Genetic and physiologic characterization of an agravitropic barley mutant
by Laura Ann Tagliani
A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in
Agronomy
Montana State University
© Copyright by Laura Ann Tagliani (1985)
Abstract:
A chemically induced mutation in barley (Hordeum vulqare L.) which results in agravitropic roots was
examined to determine genetic and physiologic controls of the trait. Crosses between wild type and
mutant plants yielded three to one F2 segregation ratios, indicating monogenic control with
gravitropism completely dominant over agravitropism. No linkage was found between agravitropism
and seven barley translocation breakpoints, the V locus on chromosome two, or the Hor-1 and Hor-2
loci on chromosome five.
No evidence of gravicurvature was found in light or dark grown agravitropic roots, although shoots
displayed complete negative gravitropism. Equivalent amounts of starch were found in root tips of
agravitropic and gravitropic plants, indicating the presence of sufficient starch in the amyloplasts for
gravitropic perception. Total root growth was similar for mutant and wild type roots, although the
mutant had fewer roots per seed and greater elongation per root. The agravitrope’s root growth was
more tolerant of inhibitory levels of applied IAA than wild type roots. Agravitropic and gravitropic
roots were equally sensitive to applications of NAA and 2,4-D. High pressure liquid chromotography
determinations of root endogenous IAA levels showed no differences between gravitropes and
agravitropes. The data from these experiments suggest that auxin controlled growth regulation may be
altered in the mutant, particularly the ability of the tissue to transport, receive, or respond to IAA. GENETIC AND PHYSIOLOGIC CHARACTERIZATION
OF AN AGRAVITROPI C BARLEY MUTANT
by
L a u r a Ann T a g l i a n i
A t h e s i s subm itted in p a r t i a l f u lf illm e n t
of the requirem ents fo r th e degree '
of
M aster o f S cience
in
Agronomy
MONTANA STATE UNIVERSITY
Bozeman, M o n t a n a
No ve mb e r 1985
A /37g
T U ?
G -Q p . = L
ii
APPROVAL
o f a t h e s i s s u b m i t t e d by
L a u r a Ann T a g l i a n i
T h i s t h e s i s h a s b ee n r e a d by e a c h member o f t h e t h e s i s c o m m i t t e e
and h a s b ee n found t o be s a t i s f a c t o r y r e g a r d i n g c o n t e n t , E n g l i s h u s a g e ,
f o r m a t, c i t a t i o n s , b i b l i o g r a p h i c s t y l e , and c o n s i s t e n c y , and i s re a d y
fo r subm ission to th e C ollege of G raduate S tudies.
C hairperson,
G r a d u a t e Committee
Approved f o r t h e M a jo r D e p artm en t
f f n
r -
' I
Date
Head, M ajor D e p a rt m e n t
Approved f o r t h e C o lle g e o f G ra d u a te S t u d i e s
/ /
Date
~ £ j —
G r a d u a t e Dean
ill
STATEMENT OF PERMISSION TO USE
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r e q u ir e m e n t s f o r a m a s t e r 's d e g re e a t Montana S t a t e U n i v e r s it y ,
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ACKNOWLEDGMENT
I sin cerely
B lake,
appreciate
as w e ll as the
the
assistan ce
o f my a d v i s o r ,
s u p p o r t o f D r s . R. L. D i t t e r l i n e ,
a n d 8. J . R o g e r s i n t h e c o m p l e t i o n o f t h i s r e s e a r c h .
extended
m utant,
to
P r o f e s s o r R.
F.
E slick
and S c o t t N is s e n f o r h i s
A cknow ledgm ents
M ark etin g Com m ittee
are
for
due
am
esp ecially
to
th e
funding t h i s
g ratefu l
p roviding
M. E. F o l e y ,
Thanks are a ls o
the
ag rav itro p ic
i n t e r e s t and t e c h n i c a l h e l p .
Science D epartm ent f o r use of t h e i r
I
for
D r . T . K.
to
M ontana
research,
W heat
and t h e
R esearch
and
P l a n t a nd S o i l
facilities.
R onald
J.
T a g lia n i,' B arbara
H.
T a g l i a n i a n d D a v i d M. Webb f o r t h e i r e n d l e s s e n c o u r a g e m e n t a n d s u p p o r t .
V
TABLE OF CONTENTS
Page
APPROVAL.......................................................................... ..................................................................; . . i i
STATEMENT OF PERMISSION TO USE...........................................................................................i i i
ACKNOWLEDGEMENT........ ..................................................................'......................................................i v
LIST OF TABLES...............................................................................................' ..................................v i i
L IS T OF FIGURES....................................................................................................................................i x
ABSTRACT..........................................................................................................................................................
INTRODUCTION...............................
I
LITERATURE REVIEW....................................................................
2
G e n e t i c A n a l y s i s ..........................: .........................................................................................2
I n t e r c h a n g e Chromosome B e h a v i o r .................................................................... 2
L i n k a g e A n a l y s i s .......................................................................................................... 6
R o o t G r a v i t r o p i s m .................................................................................................................... 9
P e r c e p t i o n .................................................................................... '...................... '........... 9
H o r m o n a l R e s p o n s e ..................................................................................................... 11
I o n i c R e s p o n s e .............................................................................................................13
A g r a v i t r o p i c M u t a n t s ..............................................................................................14
GENETIC ANALYSIS................................................................................................................................. 16
M a t e r i a l s a n d M e t h o d s . . . ...................................................................................................16
G e n e t i c S t o c k ................................................................................................................16
P o p u l a t i o n A n a l y s i s .....................' . ............ ......................................................... 18
L i n k a g e A n a l y s i s ...........................................................................
19
R e s u l t s a n d D i s c u s s i o n ..................................................................................................... 21
G e n e t i c S t o c k ............................................................................................................... 21
P o p u l a t i o n A n a l y s i s ................................................................................................ 21
L i n k a g e A n a l y s i s ....................................................................................................... 23
AGRAVITROPIC ROOT RESPONSE........................................................................................................29
M a t e r i a l s a n d M e t h o d s ........................................................................................................29
A g r a v i t r o p i c G r o w t h ................................................................................................ 29.
R o o t T i p S t a r c h C o n t e n t ...................................................................................... 30
E x o g e n o u s A u x i n S e n s i t i v i t y .....................................................
31
E n d o g e n o u s A u x i n C o n t e n t ........................................................................... . . . 1 3 1
vi
TABLE OF CONTENTS— C o n t i n u e d
Page
R e s u l t s a n d D i s c u s s i o n ............................
33
A g r a v i t r o p i c G r o w t h ....................... •............................... ..................................... 33
R o o t T i p S t a r c h C o n t e n t ................................. ■:...............................................34
E x o g e n o u s A u x i n S e n s i t i v i t y ........................................................................... 36
E n d o g e n o u s A u x i n C o n t e n t . ................................. .. ; .......................................39
SUMMARY AND CONCLUSIONS............................................................................................................... 42
LITERATURE CITED
45
vii
LIST OF TABLES
Page
1.
T r a n s l o c a t i o n s , chromosom al b r e a k p o i n t s , and a u t h o r i t i e s
fo r th e b a rle y l e t h a l tr a n s lo c a tio n t e s t e r s e t used to
d e t e r m i n e l i n k a g e t o a g r a v i t r o p i s m ..................................................................... 19
2.
F2 s e g r e g a t i o n d a t a and c h i - s q u a r e v a l u e s f o r c r o s s e s .
betw een t h e a g r a v i t r o p i c m u tan t and w ild ty p e b a r l e y
p l a n t s .................................... ................... ....................................................................................21
3.
R a t i o o f homozygotes t o h e t e r o z y g o t e s f o r B and C b a r l e y
h o r d e i n b a n d i n g p a t t e r n s i n two i n b r e d g e n e r a t i o n s o f
t h e a g r a v i t r o p i c p o p u l a t i o n ........................................................................................ 22
4.
F 2 S e g r e g a t i o n d a t a and c h i - s q u a r e v a l u e s f o r homozygous
g r a v i t r o p e s t o h e t e r o z y g o u s g r a v i t r o p e s from c r o s s e s
b e tw e e n t h e a g r a v i t r o p i c b a r l e y m u t a n t and t h e l e t h a l
t r a n s l o c a t i o n t e s t e r s e t ................................................................................................ 25
5.
F 2 s e g r e g a t i o n d a t a and c h i - s q u a r e v a l u e s f o r s e m i ­
s t e r i l i t y t o f e r t i l i t y in r e l a t i o n t o g r a v i t r o p i c genotype
f o r c r o s s e s b e tw e e n t h e a g r a v i t r o p i c b a r l e y m u t a n t and
t h e l e t h a l t r a n s l o c a t i o n t e s t e r s e t . ' ................................................................. 26
6.
F2 s e g r e g a t i o n d a t a and c h i - s q u a r e v a l u e s f o r number
o f k e r n e l r o ws p e r s p i k e i n r e l a t i o n t o a g r a v i t r o p i s m
from c r o s s e s b e tw e e n t h e a g r a v i t r o p i c b a r l e y m u t a n t
a n d t h e l e t h a l t r a n s l o c a t i o n t e s t e r s e t ............... ............... •....................... 28
7.
F2 s e g r e g a t i o n d a t a and c h i - s q u a r e v a l u e s f o r t h e B and
C h o rd e in banding p a t t e r n s in r e l a t i o n to a g ra v itro p ism
from s e l f ed a g r a v i t r o p i c and g r a v i t r o p i c h e t e r o z y g o u s
p l a n t s ..................................................
28
8.
D e g r e e s o f c u r v a t u r e o f l i g h t a n d d a r k g r ow n r o o t s o f
t h e a g r a v i t r o p i c b a r l e y m u tan t and g r a v i t r o p i c s e e d l i n g s
a t f o u r t i m e i n t e r v a l s f o l l o w i n g g r a v i s t i m u l a t i o n ................................ 33
9.
T o t a l r o o t g ro w th , r o o t s p e r s e e d l i n g s , and l e n g t h p e r
ro o t a t t h r e e tim e i n t e r v a l s fo llo w in g im b ib itio n f o r the
a g r a v i t r o p i c b a r l e y m u t a n t a n d g r a v i t r o p i c s e e d l i n g s .......................... 34
viii
LIST OF T A B L E S - - C o i i t i n u e d
-Page
1 0.
S t a r c h c o n t e n t (nm a n h y d r o u s g l u c o s e e q u i v a l e n t s ) p e r u g
p r o t e i n o f 20 Imm r o o t t i p s a m p l e s f o r t h e a g r a v i t r o p i c
b a r l e y m u t a n t a n d g r a v i t r o p i c s e e d l i n g s .............'.......................................... 35
11 .
F r e e IAA c o n t e n t p e r g r a m FW o f p r i m a r y r o o t s f o r p a r e n t s
a n d F 2 p r o g e n y o f B e t z e s X a g r a v i t r o p e 107 a n d B e t z e s
X a g r a v i t r o p e 90 c r o s s e s , a n d r a n d o m 1983 a g r a v i t r o p i c
a n d g r a v i t r o p i c p l a n t s ...................................................................................................40
LIST OF FIGURES
Page
1.
D iagram m atic r e p r e s e n t a t i o n o f t r a n s l o c a t i o n h e te r o z y g o te
p a i r i n g a n d s e p a r a t i o n d u r i n g m e i o s i s ................................................................ 3
2.
D iag ram m atic r e p r e s e n t a t i o n o f m e i o t i c p a i r i n g and s e p a ­
ra tio n of a tra n s lo c a tio n heterozygote w ith i n t e r s t i t i a l
r e c o m b i n a t i o n ........................................................................................................... '..............5
3.
Diagram m atic r e p r e s e n t a t i o n o f t h e s e g r e g a t i o n o f a
s e l f - p o l l i n a t e d l e t h a l t r a n s l o c a t i o n h e t e r o z y g o t e ...................................8
4.
O r i g i n o f t h e a g r a v i t r o p i c b a r l e y m u t a n t . The p h e n o t y p e
an d number o f p l a n t s grown i n s e l f - p o l l i n a t e d f i e l d
p o p u l a t i o n s a r e s hown f o r 1980 t h r o u g h 1 9 8 4 ................................................17
5.
D i a g r a m m a t i c r e p r e s e n t a t i o n o f Fg s e g r e g a t i o n w i t h
l i n k a g e betw een a g r a v i t r o p i s m and a l e t h a l t r a n s l o c a t i o n
b r e a k p o i n t ................................................................................................................................... 24
6.
D i a g r a m m a t i c r e p r e s e n t a t i o n o f c hr p mo s o m e s e g m e n t s o f
t h e b a r l e y genome t e s t e d b y c r o s s e s b e t w e e n t h e a g r a v i ­
t r o p i c m u t a n t and t h e l e t h a l t r a n s l o c a t i o n t e s t e r s e t ,
a n d H o r - I , H o r - 2 , a n d V m a r k e r g e n e s ...............................27
7.
I n h i b i t i o n o f b a r l e y r o o t grow th f o r a g r a v i t r o p e s and
g r a v i t r o p e s w i t h i n c r e a s i n g c o n c e n t r a t i o n s o f NAA.
T r e a t m e n t m e a n s _+ s t a n d a r d e r r o r s a r e e x p r e s s e d
a s p e r c e n t o f c o n t r o l ..................................................................................................... 37
8.
I n h i b i t i o n o f b a r l e y r o o t grow th f o r a g r a v i t r o p e s and
g r a v it r o p e s w ith i n c r e a s in g c o n c e n tr a tio n s o f 2,4-D .
T r e a t m e n t m e a n s _+ s t a n d a r d e r r o r s a r e e x p r e s s e d
a s p e r c e n t o f c o n t r o l ......................................................................................................37
9.
I n h i b i t i o n o f b a r l e y r o o t grow th f o r a g r a v i t r o p e s and
g r a v i t r o p e s w i t h i n c r e a s i n g c o n c e n t r a t i o n s o f IAA.
T r e a t m e n t m e a n s _+ s t a n d a r d e r r o r s a r e e x p r e s s e d
a s p e r c e n t o f c o n t r o l ..........................; ..................................................... ................... 38
10.
R e p r e s e n t a t i v e HPLC c h r o m a t o g r a m o f a b a r l e y r o o t IAA
e x t r a c t i o n sam ple.
Th e IAA i s d e t e c t e d b y f l u o r e s c e n c e
w i t h a p e a k r e t e n t i o n t i m e o f 1 2 . 8 5 m i n u t e s . ............................................39
X
ABSTRACT
A c h e m i c a l l y i n d u c e d m u t a t i o n i n b a r l e y (Hordeum v u l q a r e L.) w h i c h
r e s u l t s i n a g r a v i t r o p i c r o o t s was e x a m in e d t o d e t e r m i n e g e n e t i c and
p h y sio lo g ic c o n tro ls of the t r a i t .
C r o s s e s b e tw e e n w i l d t y p e and
m u t a n t p l a n t s y i e l d e d t h r e e t o o n e Fg s e g r e g a t i o n r a t i o s , i n d i c a t i n g
m o n o g en ic c o n t r o l w ith g r a v i t r o p i s m c o m p letely dom inant over
agravitropism .
No l i n k a g e w a s f o u n d b e t w e e n a g r a v i t r o p i s m a n d s e v e n
b a r l e y t r a n s l o c a t i o n b r e a k p o i n t s , t h e V l o c u s on c h r o m o s o m e t w o , o r t h e
H o r- I and H o r-2 l o c i on chromosom e f i v e .
No e v i d e n c e o f g r a v ! c u r v a t u r e w a s f o u n d i n l i g h t o r d a r k g r o w n
a g ra v itro p ic roots,
although shoots d isp la y e d com plete n eg ativ e
g ravitropism .
E q u i v a l e n t am ounts o f s t a r c h were found i n r o o t t i p s of
a g r a v i t r o p i c ' and g r a v i t r o p i c p l a n t s ,
in d ic a tin g th e presence of
s u f f i c i e n t s t a r c h i n the. a m y l o p l a s t s f o r g r a v i t r o p i c p e r c e p t i o n .
Total
r o o t g r o w t h was s i m i l a r f o r m u t a n t and w i l d t y p e r o o t s , a l t h o u g h t h e
m u ta n t had f e w e r r o o t s p e r se e d and g r e a t e r e l o n g a t i o n p e r r o o t .
The
a g r a v i t r o p e ’s r o o t g r o w t h w a s m o r e t o l e r a n t o f i n h i b i t o r y l e v e l s o f
a p p l i e d IAA t h a n w i l d t y p e r o o t s .
A g r a v i t r o p i c and g r a v i t r o p i c r o o t s
w e r e e q u a l l y s e n s i t i v e t o a p p l i c a t i o n s o f NAA a nd 2 , 4 - D .
High p r e s s u r e
l i q u i d c h r o m o t o g r a p h y d e t e r m i n a t i o n s o f r o o t e n d o g e n o u s IAA l e v e l s
showed no d i f f e r e n c e s b e t w e e n g r a v i t r o p e s and a g r a v i t r o p e s .
The d a t a
from t h e s e e x p e rim e n ts s u g g e s t t h a t a u x in c o n t r o l l e d g ro w th r e g u l a t i o n
may b e a l t e r e d i n t h e m u t a n t , p a r t i c u l a r l y t h e a b i l i t y o f t h e t i s s u e t o
t r a n s p o r t , r e c e i v e , o r r e s p o n d t o IAA.
I
INTRODUCTION
Novel q u a l i t a t i v e
m utants
are
v aluable
research
to o ls.
Such
m u ta n ts can be u t i l i z e d as g e n e t i c m a rk e rs in l i n k a g e s t u d i e s and in
the c o n s tru c tio n
o f g e n e t i c maps.
D eterm in atio n s of p h y sio lo g ic a l
m echanisms o r b io c h e m ic a l pathw ays have a l s o
been
facilitated
by
the
use of m utants.
M utatio n s a r i s e spo n tan eo u sly o r thro u g h induced m u tag en e sis,
a r e i d e n t i f i e d by a change i n p h e n o ty p e .
g en etic
or p h y sio lo g ic
research
E ffe c tiv e use of
req u ires
the
and
a m utant in
e s ta b lis h m e n t of the
g en o ty p e and b i o c h e m i c a l a l t e r a t i o n o f t h e m utant.
The p u r p o s e
of
th is
work
was t o
ch aracterize
p h y s io lo g ic m echanism s c o n f e r r in g b a r le y
agravitropism .
chromosome c a r r y i n g t h i s
designed
to
g en etic
(H o r d e u m v u l g a r e
L.)
and
root
The g o a l o f t h e g e n e t i c s t u d i e s was t o i d e n t i f y t h e
number o f genes c o n t r o l l i n g a g r a v i t r o p i s m ,
the
th e
in v estig ate
m utation.
M echanism s
th e type o f gene ac tio n ,
and
The p h y s i o l o g i c a l s t u d i e s w e r e
for
the
m u ta n t's
lack
of
root ■
<
g rav iresp o n se.
R esults
from
th is
w ork can be u t i l i z e d
g r a v itr o p ic physiology o r b a rle y g e n e tic s
research.
in g e n e ra l
2
LITERATURE REVIEW
G enetic A nalysis
I n t e r c h a n g e Chromosome B e h a v i o r
S trick b erg er
translocated
is
(1976) an d S y b e n g a (1975) d e s c r i b e t h e b e h a v i o r o f ■
chromosomes.
A reciprocal
translocation,
interchange,
an e x c h a n g e o f s e g m e n ts o f nonhomo lo g o n s c h ro m o so m es.
l o c a t i o n h e t e r o z y g o t e i s an i n d i v i d u a l t h a t c a r r i e s
tran slo cated
complement.
chrom osom es,
ring of
four
S eparation
alternate,
is
of
the
com plete,
a
fu ll
I,
or
chromosom e
homologous segm ents o f t r a n s l o c a t i o n
form ed due
q u ad riv alen t
adjacent
norm al
retain in g
A tran s­
tw o n o rm a l and two
form ing a c ro ss c o n fig u ra tio n .
often
as a folded rin g ,
tw o
thereby
In m eioti.c p rophase,
h eterozygotes p a ir,
the
or
to
term in alizatio n
of
occur
com binations;
can
adjacent
At d i a k i n e s i s , a
2.
in
th ree
chiasm ata.
A lternate d isju n c tio n
appears
t h e t w o t r a n s l o c a t e d c h r o m o s o m e s move t o o n e p o l e a n d
chrom osom es
v i a b l e gam etes.
move' t o
the
o t h e r -pole)
resu ltin g
A d ja c e n t d i s j u n c t i o n o c c u r s i n an open r i n g ,
w i t h one t r a n s l o c a t e d and one n o r m a l chrom osom e m oving t o g e t h e r .
resu lts
in
d u p licatio n
lethal.
In
adjacent
t h e same p o l e ,
(F igure
I
and d e f i c i e n c y
separation,
a n d i n a d j a c e n t 2,
gam etes,
nonhomologous
w hich
This
are
usually
centrom eres
move t o
h o m o l o g o u s c e n t r o m e r e s move t o g e t h e r
I ).
Centrom ere d i s j u n c t i o n ty p e s a re
of
in
50% a l t e r n a t e ,
25% a d j a c e n t
I
ex p ected to o ccu r a t a frequency
and
25% a d j a c e n t
2 o rien tatio n s
3
Figure
I.
D ia g ra m m a tic r e p r e s e n t a t i o n o f tr a n s lo c a tio n heterozygote
p a i r i n g and s e p a r a t i o n d u r i n g m e i o s i s .
TRANSLOCATION
PACHYTENE
HETEROZYGOTE
CROSS CONFIGURATION
I
ALTERNATE
ADJACENT I
ADJACENT 2
DISJUNCTION
DISJUNCTION
DISJUNCTION
DUPLIC ATION/DEFICIENC Y
DUPLIC ATION/DEFICIENCY
COMPLETE
GAMETES
GAMETES
GAMETES
4
(R ickards
1983).
d eficien cies
only
( Burnham 1 9 5 6 ) ,
th o se gam etes
v i a b l e . • Hence,
nonviable,
yielding
than the
( S m i t h 1 9 51 ).
re su ltin g
of
expected
cross co n fig u ratio n ,
chrom osom al
altern ate
eggs
d isju n ctio n
and p o l l e n
s h o u ld be
produced
w ould be
50%,
heterozygotes
r a n g in g from
in
usually
to
12%
a g r e a t e r occurance
B u rn ha m e t a I .
also v arie s
is
3 1.6% ( H a n s o n 1 9 5 2 )
probably in d ic a te s
(Ramage 1963;
barley
1954; Burnham a n d
w ith en v iro n m e n t and s p e c i f i c
tran slo catio n
break
crossover,
point,
and a d j a c e n t
gam etes
heterozygote
chromosom es are in the m eio tic
c ro s s o v e r can o c c u r in p a ire d re g io n s
In te rs titia l
d eficien cy
m ost
( M i l a n 1964 ).
When t r a n s l o c a t i o n
A lternate
the
tran slo catio n
1956). S t e r i l i t y
1975).
from
Reduced s t e r i l i t y
interchanges
to lera te
50% s e e d s t e r i l i t y .
of a lte r n a te d isju n c tio n
H agberg
cannot
th e r e f o r e in the absence o f recom bination,
one h a l f o f
S em isterility
less
D ip lo id s
alters
b etw een
gam ete
I d isju n ctio n
(Burnham
1956).
th e
ce n tro m ere
v iab ility
re su lt
(Sybenga
(Hanson
1952).
i n 50% d u p l i c a t i o n
M cC lintock
(1945)
and
and
and
Burnham
(1950) o b s e r v e d t h a t c h r o m o s o m e s i n v o l v e d i n i n t e r s t i t i a l c r o s s o v e r
pass to opposite poles,
Du e t o
m eio tic
e s s e n tia lly e lim in a tin g adjacent 2 segregation.
m etaphase o rie n ta tio n s ,
re c o v e re d s o l e l y from a d j a c e n t
a lte rn a te d isjunction
The o b s e r v e d
expected
(Hanson 1952).
I segregation.
V ia b le g am ete s from
c o n t a i n o n ly p a r e n t a l chromosomes
amount o f
h e t e r o z y g o t e s d e p e n d s on t h e
and t h e
i n t e r s t i t i a l recom binants are
crossover
in terstitia l
recom bination
( F i g u r e 2).
in
interchange
frequency o f centrom ere d is j u n c t io n types
frequency
for
the
two
in terstitia l
An a b u n d a n c e o f a l t e r n a t e d i s j u n c t i o n
regions
in c re a s e s the
5
F ig u re 2.
D ia g r a m m a tic r e p r e s e n t a t i o n o f m e i o t i c p a i r i n g and
se p a ra tio n of a tr a n s lo c a tio n heterozygote w ith i n t e r s t i t i a l
r e c o m b i n a t i o n (* i n d i c a t e s c r o s s o v e r c h r o m a t i d s ) .
TRANSLOCATION HETEROZYGOTE
WITH INTERSTITIAL CROSSOVER
ALTERNATE DISJUNCTION
<
( =
)
COMPLETE GAMETES
=
)
<
=
)
COMPLETE GAMETES
...........
DUPLICATION/DEFICIENCY
DUPLICATION/DEFICIENCY
DUPLICATION/DEFICIENCY
GAMETES
GAMETES
GAMETES
6
recovery
of p a r e n t a l gam etes
recom bination.
to rsio n s
P airing
and d e c r e a s e s
and c r o s s o v e r
the
observed
may a l s o
be
am ount o f
reduced
due
to
around th e break p o in t o r h e te ro c h ro m a tin n ea r th e centrom ere
(Schulz-Schaeff e r
1980 ).
recom binant recovery
DeVries
is
(1983)
due to
concluded t h a t
in
rye,
the
low
d i s t u r b a n c e i n p a i r i n g and c r o s s o v e r ,
r a t h e r t h a n an e x c e s s o f a l t e r n a t e d i s j u n c t i o n .
The a m o u n t o f i n t e r s t i t i a l c r o s s o v e r in b a r l e y i s m ask ed by t h e
increased
frequency of
Burnham an d H a g b e rg
alternate
1956;
disjunction
Ramage
1963).
(Ha ns on
and Kram er
1949;
K ram er and B la n d e r
(1961)
e s t i m a t e d t h a t 16.7% w a s t h e m a x i m u m r e c o m b i n a n t r e c o v e r y i n b a r l e y
tra n slo ca tio n s.
D eV ries
reco m b in atio n
cy to lo g ical
and
(1983)
argues
d ata,
th at
on
altern ate
th e
b asis
of
d isju n ctio n
of
c h r o m o s o m e s w i t h i n t e r s t i t i a l c h i a s m a s h o u l d b e a s s u m e d a t 50%, n o t 75%
as
K ram er
and
in te rstitia l
d isju n ctio n
B lander
(1961)
reco m b in atio n
of
chrom osom es
used.
was
a n d B u rn h am 1965;
m asked
w ithout
decreased recovery of i n t e r s t i t i a l
D eV ries
due
chiasm a.
( 1983)
to
found
higher
R eg ard less
altern ate
of
cause,
recom binants occurs in b a rle y
R am ag e a n d S u n e s o n 1961;
th at
(Ka sha
Ramage 1966) .
Linkage A n a ly s is
B arley
translocations
have been used
b a s e d on t h e a s s o c i a t i o n o f g e n e t i c
1964; J o a c h im
T u l e e n 1 9 71 ).
Se I f - p o l l i n a t e d
hom ozygote
fertility ,
linkage
and
studies,
se m isterility
a nd a r e
(N iIan
1947; H a n so n and K r a m e r 1950; K a sh a a n d B urnham 1965;
one t r a n s l o c a t i o n
norm al
traits
in
tran slo ca tio n
hom ozygote:
(Ramage
heterozygotes
segregate
tw o t r a n s l o c a t i o n h e te ro z y g o te s:
1963).
The
hom ozygotes
have
one
norm al
but the interchange heterozygotes e x h ib it s e m is te r ility ,
due
7
to
adjacent
segregation
d isju n ctio n
ratio
in
m eiosis.
i s one s e m i s t e r i l e :
T herefore,
the
phenotypic
one f e r t i l e .
L e th a l t r a n s l o c a t i o n m u ta n ts e x p r e s s an a b e r r a n t s e g r e g a t i o n r a t i o
o f z e r o t r a n s l o c a t i o n hom o zy g o tes: tw o t r a n s l o c a t i o n h e t e r o z y g o t e s : one
n orm al homozygote,
indicating
the presence o f a recessive
linked to the tr a n s lo c a tio n b r e a k p o i n t
E lim in atin g
the
tran slo catio n
hom ozygote
In ten sity
info rm atio n
av a ila b le
p recisio n
in
stu d ies
lin k ag e
per
class
F2 p la n t,
(B ig g erstaff
segregation r a tio of these le th a l
one f e r t i l e .
(B ig g erstaff
1981)
1981).
is
The
tw o
gene
(F igure
in creases
thereby
tran slo ca tio n s
lethal
3).
linkage
in creasin g
phenotypic
sem isterile:
L inkage i s d e t e r m i n e d by l a c k o f i n d e p e n d e n t s e g r e g a t i o n
i n t h e F2 g e n e r a t i o n i n c r o s s e s b e t w e e n t r a n s l o c a t i o n h e t e r o z y g o t e s and
m utants to
be mapped
M utations
examined.
(T u l e e n 1971) .
linked
to
sp ecific
The B a n d C h o r d e i n
m arker
storage
traits
proteins
can
sim ilarly
of barley
are
be
encoded
b y t h e H o r - 2 a n d H o r - I l o c i ( D o l l a n d B ro w n 1 979; S h e w r y e t a I. 1980) ,
and a r e
lo cated
on t h e
short
arm o f chrom osom e
fiv e
(Jensen
1984).
T e c h n i q u e s f o r c h a r a c t e r i z a t i o n o f t h e s e p r o t e i n s by p o l y a c r y l a m i d e g e l
electro p h o resis
are
A ndersen
The H o r-2
1981).
w ell
d escribed
(B lake
and H o r - 1 l o c i a r e
1980) a n d h a v e b e e n u s e d t o c h a r a c t e r i z e
(Hash a n d B l a k e 1981; J e n s e n e t a l .
e t al.
1982,-
Shewry e t a l .
A m orphological t r a i t
k e r n e l rows p e r sp ik e.
the
et
al.
lin k ed
.1982;
D o l l •a n d
(Shewry e t a l.
l i n k a g e w i t h t h e MI - a l o c u s
1980), and t h e H o r-3
locus
(Blake
1983) o f c h r o m o s o m e f i v e .
for barley
This c h a ra c te r
lo n g arm o f chromosome two,
li n k a g e a n a l y s i s i s t h e number o f
is
c o n t r o l l e d by t h e V l o c u s on
w ith tw o-row head ty p e s dom inant over
8
F ig u re 3.
D iagram m atic r e p r e s e n t a t i o n o f t h e s e g r e g a t i o n o f a s e l f p o l l i n a t e d l e t h a l t r a n s l o c a t i o n h e t e r o z y g o t e (I d e n o t e s
recessive le th a l a lle le ) .
I
♦ .....
TRANSLOCATION HETEROZYGOTE
VIABLE GAMETES
WITH LETHAL GENE
SELF-POLLINATION
I
..........
t
I
____
I
IM iiim m iM ^ IIIiii
IM M M M * M M M 4
*iim
I TRANSLOCATION
HOMOZYGOTE
LETHAL
IM M M IM M M M * IM M m m m W
:
2 TRANSLOCATION
I NORMAL
HETEROZYGOTES
HOMOZYGOTE
SEMISTERILE
FERTILE
9
six-row
(N iIan
1964).
T h e _I l o c u s o n c h r o m o s o m e f o u r c o n t r o l s
morphology o f th e l a t e r a l f l o r e t s , b u t t h e e x p r e s s io n o f s ix - r o w
is
n o t a f f e c t e d by t h i s
gene
the
spikes
(Haus 19 75 ).
Root G ra v itr o p is m
Perception
Prim ary
p lan t
g ravitropism .
stim u lu s.
ro o ts
Th e f i r s t
The
grow ing to w ard s
ste p in a tro p ic
starch
stato lith
1976).
explanation
M ovement
statocyte ce lls,
g rav ity
c o rre la te d w ith graviresponse
1984).
of
starch
cells
c y lin d e r of the
fo rm u la te d .in
1975)
1900
and re m a in s t h e
(Audus
1979;
stato lith s,
Juniper
w ithin
the
A m y lo p la s t movement i s h i g h l y
( S h e n - M i l l e r a n d H i n c h m a n 1 97 4 ) , a n d t h e y
functional s ta to lith s
Root s t a t o c y t e
ce n tral
( s e e Audus
c o n s titu te s perception.
are regarded as the
was
of p la n t graviperception
w ith
ex h ib it p o sitiv e
response is p ercep tio n of the
theory
i n d e p e n d e n t l y b y H a b e r l a n d t a n d Nemec
most v ia b le
g rav ity
have been
root
cap
in p l a n ts
identified
(Audus 1979;
as
the
( J u n i p e r and F re n c h
Mo ore
colum ella
1970;
or
W ilkins
1975).
Several
response.
organelles
fo rm s.o f
w hich
stops
is
et
al.
sedim ent
(Audus
1979;.
gravitropic
w ith am yloplast
Juniper
lin k
am yloplasts
Due t o t h e i r s i z e a n d d e n s i t y ,
gravicurvature
rem oval
evidence
(H illm an
1966;
lo s t w ith s ta rc h
rap id ly
response,
and
and W i l k i n s
Cercek
rem oval
1970)
to
be
and Hinchman
response
1982)
g rav itro p ic
am yloplasts' are
enough
Shen-M iller
w ith
regeneration.
correlated
19 74 ).
return
and r o o t
th e only
cap
is
Root
cap
correlated
(B arlow
G ravitropic
from s t a t o c y t e s and r e s p o n s e
w ith
1974,;
response
retu rn s
w ith
10
sta rc h reform ation
( I v e r s e n 1969; G r i s a f i e t a l . 1984; K aufm an e t a I.
1984) .
Amyl o p l a s t s
p erception .
m a y s L.)
that
may i n t e r a c t w i t h o t h e r c e l l u l a r c o m p o n e n t s i n g r a v i -
M oore (1983) r e p o r t e d t h a t g r a v i s t i m u l a t e d , m a i z e (Zea
root stato cy te organelles
am yloplast
Dictyosom e
m ovem ent' alo n e
activ ity
(Shen-M i H e r
were d i s t r i b u t e d
did
not
account
for
is
altered
w ith
and d i s t r i b u t i o n
and H inchm an
endoplasm ic re tic u lu m
1974).
Juniper
gravity,
w alls
w ith in
the
ce ll,
t h e ER r e t u r n s t o ' i t s
and
that
d istrib u tio n .
gravistim ulation
French
(1970)
found
running p a r a l l e l to
W ith g r a v i s t i m u l a t i o n ,
follow ing
and
reo rien tatio n
t h e ER
tow ards
norm al d i s t r i b u t i o n r e l a t i v e to the c e l l
( J u n i p e r and F r e n c h 1973).
statocytes,
and
(ER) i n m a i z e r o o t s t a t o c y t e s
t h e n u c l e a r m em brane and c e l l w a l l s .
agg reg ates
asym m etrically
In c r e s s
(L e p i d i u m s a t i v u m L . ) r o o t
t h e ER f o r m s a c u p - s h a p e d a g g r e g r a t i o n a t t h e
low er sid e of
t h e c e l l t h a t d o e s n o t move w i t h a c h a n g e i n o r i e n t a t i o n
(Vol k m a n n a n d
S iev ers
w hich
1979).
changes
pressure
rep o rts
A m yloplasts r e s tin g
w ith
reo rien tatio n
o n t h e ER m a y e x e r t
and
am yloplast
c h a n g e may b e a f o r m o f p e r c e p t i o n .
of
am yloplasts
(Ransom a n d M oo re
1983;
in
stato cy tes
do n o t e x h i b i t a p a r t i c u l a r ER d i s t r i b u t i o n
How t h e p h y s i c a l s t i m u l u s i s
r e s p o n s e i s u n k n o w n ( Moore 1984).
in th e l i t e r a t u r e
V olkm ann
av ailab le
and
to
m ovem ent.
Y et,
w h ich do n o t
Moore and M c C le le n
1 98 3) ,
th ere
are
T his
also
c o n ta c t the
and s t a t o c y t e s
(Juniper
tran sm itte d
a pressure
into
ER
that
1 97 6) .
a. p h y s i o l o g i c a l
Numerous t h e o r i e s h a v e b e e n r e v i e w e d
( P e r b a l 1978; J u n i p e r 1976; Audus 1975; M oore 1984;
S iev ers
1979)
support those
but
theories.
little
experim ental
evidence
is
11
Hormonal R es p o n s e
The r e s u l t o f g r a v i s t i m u l u s
elongation
zone o f th e
proposed a h y p o th e s is
They s u g g e s t e d t h a t
to
the
low er s id e
root.
to
Audus
1975;
in a h o riz o n ta l
Juniper
in
response
1976;
is
1957).
d eterm in e
root
in h ib itin g
ce ll
S ince th en , th e re
if
auxins
graviresponse
w ith
a general
or o th er
(see
G ibbons
inhib itio n
and W ilk in s
e v i d e n c e o f a g r o w t h i n h i b i t o r moving b a s i p e t a l l y
graviresponse.
laterally
review s,-
1979) .
associated
and B ro w n b rid g e
to
in
W ilkins
the
( s e e Audus 1979).
auxin is d is p la c e d
dow nw ard c u r v a t u r e :
functio n in g
in
C h o l o d n y a n d We n t i n d e p e n d e n t l y
root,
in v estig atio n s
are
Root c u r v a tu r e
(A udus
1926,
in su p ra o p tim al c o n c e n tra tio n s,
have been num erous
in h ib ito rs
In
c u rv atu re tow ards g ra v ity
explain g ra v itro p ic
e l o n g a t i o n and r e s u l t i n g
grow th
is
Removal o f one h a l f
of the
o f grow th
(1970)
from t h e
provide
r o o t cap in
r o o t cap in m aize s e e d l i n g s
c a u se s c u r v a tu r e to w a rd s th e s id e w ith th e i n t a c t cap, r e g a r d l e s s of
g ra v ity .
M echanical b a r r i e r s
p l a c e d b etw een t h e apex and e l o n g a t i o n
z o n e o f m a i z e a n d p e a (P i s u m s a t i v u m L.) r o o t s p r o v i d e d s i m i l a r r e s u l t s
(Shaw
and
W ilkins
u n trea ted side,
1973).
C urvature
alw ays
occured
in d ic a tin g t h a t a grow th i n h i b it o r in
tow ards
the
th e
cap
root
moves b a s i p e t a l l y t o th e e l o n g a t i o n zone. . In a s i m i l a r e x p e r im e n t,
P ile t
(1973)
showed t h a t
a grow th
in h ib ito r
in
the
root
cap
moves
l a t e r a l l y downward in h o r i z o n t a l r o o t s , th e r e b y in d u c in g c u r v a t u r e .
In d o leacetic
present
P ilet
in ro o t t i p s
1974).
. (I v e r s e n
acid
et
Its
al.
(IAA) , a n a t u r a l I y o c c u r i n g p l a n t
(B ridges e t a l.
movement w i t h i n
1971;
B a t r a e t a I.
1 973) a n d r o o t c a p s
the
root is
p rim arily
1975;
Juniper
1 97 6) .
auxin,
is
( R i v i e r and
acropetal
A pplication of
12
IAA a n d t w o s y n t h e t i c a u x i n s , n a p h t h a l e n e a c e t i c a c i d
d ic h loro p h en o x y acetic
19 67 ).
acid
A pplied exogenously,
(2,4-D ),
IAA
in h ib its
red istrib u tes
side of h o riz o n ta lly stim u la te d ro o ts
m en t s ' o f e n d o g e n o u s IAA d i s t r i b u t i o n
asym m etry
w ith
root
g ra v !stim u latio n
grow th
laterally
(K onings 1967).
i n m aize
(M ertens
(NAA) a n d 2 , 4 -
roots
to
of
the
s h o w e d no
lateral
1983).
Root
2 ,3 ,5 -triio d o b en z o ic
a c i d (TIBA), a p o l a r a u x i n t r a n s p o r t i n h i b i t o r (K o n in g s 1969).
(1975)
su g g ests
th at
IAA i s
necessary
for
lower
Y et, m e a s u r e ­
and W e i l e r
g r a v i r e s p o n s e ca n be i n h i b i t e d by a p p l i c a t i o n
(A n d r e a e
Audus
g ra v ic u rv atu re, but
the
r e g u l a t i o n o f g r a v i r e s p o n s e may b e d u e t o a n o t h e r i n h i b i t o r w h i c h m o ve s
b asip etally
from t h e r o o t cap.
A u x i n a p p l i e d t o r o o t s i n h i b i t s g r o w t h by s t i m u l a t i n g e t h y l e n e
production
(C hadwick and Burg
have
used
been
to
1 96 7) .
d em onstrate
Ethylene b io s y n th e s is
the
i n h i b i t o r in auxin t r e a t e d t i s s u e
ro le
of
ethylene
(Mu I k e y e t a l .
inhibitors
as
1982a,
a grow th
1982b).
l e v e l s o f a p p l i e d a u x i n s c a u s e no a l t e r a t i o n o f r o o t g r o w t h .
the
presence
of
ethylene
stim ulated
by
the
in teractio n
has been
a n d B u r g 1967;
basipetal
19 7 4 ;
auxins.
T his
suggested as
1974;
(P ilet
Iversen
in h ib ito rs,
au x in -eth y len e
a factor
W heeler and S a l i s b u r y
A bscisic acid
and Audus
biosynthesis
1975).
et
a I.
et
al.
1977)
and
Root e l o n g a tio n i s
1977).
grow th
(1983)
found t h a t
the
grow th
is
reg u latin g
graviresponse
P ile t
in
its
m aize
root
movement
(Chadwick
caps
in
(Kundu
roots
is
i n h i b i t e d b y ABA ( M i l b o r r o w
(1975)
d etected
r e d i s t r i b u t i o n o f ABA d o w n w a r d i n h o r i z o n t a l r o o t s ,
W eiler
Y et, in
19 80 ).
(ABA) h a s b e e n i d e n t i f i e d
R iv ier
in
root
Low
a s y m m e t ry was s l i g h t ,
a
lateral
b u t M e r te n s and
tran sien t,
a nd t o o
13
late
to
W ain
induce
1975),
(W ilkins
grav!response.
or
exposure
an d W ain
1974),
' LG1 1 ' m a i z e m u t a n t .
Yet,
E x o g e n o u s ABA a p p l i c a t i o n
to
w hite
lig h t
is
req u ired
to
for
Smith e t a l.
induce
( W ilk in s and
ABA p r o d u c t i o n
root g rav iresp o n se
in th e
(1985) f o u n d n o r m a l g r a v i t r o p i c
r e s p o n s e i n ABA d e p l e t e d r o o t s o f o t h e r m a i z e c u l t i v a r s .
X anthoxin,
ABA a n a l o g u e
Burden
w ith
sim ila r properties
as
ABA ( T a y l o r a n d
may a l s o b e a g r o w t h i n h i b i t o r i n g r a v i r e s p o n s e
an
1970),
(Audus 1975; I v e r s e n e t
a l . 1977; Kundu and Audus 1974).
G ib b erellic
h o rizo n tal
1974).
acid
roots
re d istrib u tes
laterally
(W e b ste r and W ilk in s
1974;
to
E l-A ntably
G ibberellin s stim u la te root elo n g atio n
i n h i b i t e lo n g a tio n a t high c o n c e n tra tio n s
A ro le for g ib b e re llic
(W ilkins
the upper side of
and L arso n
(E l H i n n a w y 1973) an d
(E l-A n tab ly and L arson
197 4).
a c i d in g e o r e s p o n s e h a s y e t t o be e s t a b l i s h e d
1979).
I o n ic Response
Auxins s t i m u l a t e p r o to n e x t r u s i o n ,
and c e l l
is
enlargem ent
evidence
that
(Rayle and C le la n d
w ith
g r a v is t i m u I a t ion,
leading to c e l l
1977).
w a ll loosening
In p la n t
auxins
shoots,
red istrib u te
f o l l o w e d by a s y m m e t r i c p r o t o n e f f l u x a n d g r a v i c u r v a t u r e
Rayle
1983;
M igliaccio
n o t as c l e a r .
inw ard
elongation
19 84 ).
In
roots
the
of
grow ing
zone,
p rotons
roots
in
show
w hile h o riz o n ta l
m aize
roots
(W rig h t and
relationship
sym m etric
roots
(Evans
acid
is
Mulkey e t a l .
1981;
Behrens e t a l .
et
efflu x
a I.
1980).
along
the
e x h i b i t e n h a n c e d e f f l u x on t h e
u p p e r s u r f a c e and r e d u c e d e f f l u x a l o n g t h e l o w e r s i d e
1981;
laterally
E xcess au x in c a u se s g ro w th i n h i b i t i o n and an a p p a re n t
movement
V e rtic ally
and R ayle
there
1982) .
( M u l k e y a n d E va n s
Conversely,
W eisenseel.
14
e t a I.
zone,
(1979)
and o u t o f th e
C alcium
1966;
re d istrib u tes
red istrib u tes
(Lee e t a l .
1983a).
(Lee e t a I.
curvature
root tip
in g r a v is tim u la te d
1976).
downward,
In
and e l o n g a t i o n
moving
calcium
(Lee e t
across
the
ro o ts,
root
tip
l a t e r a l c a l c i u m movement
ap p licatio n
al.
(Arslan-Cerim
stim u lated
laterally
Exogenous c a lc iu m
the
tissues
h o rizo n tally
Root cap rem oval i n h i b i t s
1983a).
tow ards
the
r o o t h a i r zone.
Goswam i and Audus
calcium
is
found p r o t o n s m oving i n t o
1 9 83 b) .
to
Root
ro o ts
causes
graviresponse
i n h i b i t e d by c a lc i u m c h e l a t i n g a g e n t s and r e s t o r e d by a p p l i c a t i o n o f
calciu m c h lo rid e .
g ra v istim u lated
C alcium en h an ces l a t e r a l au x in movement a c r o s s
root tip s
(Lee and E v a n s 1985).
A m y lo p lasts in the
r o o t cap c e l l s o f m a iz e , p e a , and l e t t u c e
(L a c t u c a s a t i v a L.) c o n t a i n
calcium
( 1983a )
(Chandra e t a I.
may h a v e a r o l e
1982) .
L ee e t a l .
su g g est t h a t calcium
lin k in g g r a v i s t i m u l a t i o n t o g ra v ir e s p o n s e in ro o ts.
A g r a v i tr o p ic M utants
P l a n t m u t a n t s may b e u s e d t o s t u d y g r a v i t r o p i c r e s p o n s e m e c h a n i s m s
( Vo l k m a n n a n d S i e v e r s
197 9 ) .
coleoptile
graviresponse
statocytes
(H ertel e t a l.
auxin r e d i s t r i b u t i o n
and g r a v i t r o p i c
m utant
req u ires
graviresponse
Ah a m y l o m a i z e m u t a n t e x h i b i t s
apparently
1969).
Iversen
curvature
w hite
1 98 1 ).
( 1980a,
in
the
examine
( H e r t e l e t a I . 1 9 6 9 ; O u i t r a k u l a n d H e r t e l 1969)
(H iId and H e r t e l
lig h t
for
1972).
ABA p r o d u c t i o n
( W i l k i n s a n d Wa in 1 9 7 4 ) ,
Chanson and P i l e t
sm aller am yloplasts
T his m u tan t has been used t o
as a ro o t cap g row th i n h i b i t o r
and
due t o
reduced
The ' L G l l 1 m a iz e
and p o s i t i v e
and h a s c r e a t e d
in terest
in g ra v itro p ic response
root
i n ABA
( P i l e t 1983;
An a g r a v i t r o p i c p e a m u t a n t d e s c r i b e d b y O l s e n
1980b)
has
ER d i s t r i b u t e d
throughout the
root
cap
15
co lu m ella c e lls ,
statocytes.
This a l t e r e d d i s t r i b u t i o n
gravistim ulus.
by s c r e e n i n g
r a th e r than the cup-shaped d i s t r i b u t i o n
in norm al
may d i s r u p t t r a n s m i s s i o n o f t h e
A g ra v itr o p ic A ra b id o p sis t h a l i a n a m u tan ts were i s o l a t e d
fo r auxin r e s is ta n c e
(M aher and M a r t i n d a l e
1980).
The
m u t a n t s ' r o o t s d i s p l a y l e s s g r o w t h i n h i b i t i o n d u e t o a p p l i e d IAA a n d
2,4-D t h a n c o n t r o l r o o t s .
unlinked
1984).
dom inant
Root
u ltrastru ctu re,
sedim entation
gene
anatom y
On e m u t a t i o n
w hich
stu d ies
is
leth al
y ield ed
is
recessive,
another is
an
whe n h o m o z y g o u s
(M irza e t a l .
no d i f f e r e n c e s
in
stato cy te
bu t the re c e ssiv e m utant ex h ib ite d decreased am yloplast
rates
(Olsen e t
al.
1984) .
16
GENETIC ANALYSIS
M a t e r i a l s and Methods
G e n etic S tock
The a g r a v i t r o p i c
balanced t e r t i a r y
d ieth y l
su lfate
b a r l e y m u ta n t a r o s e from c h e m ic a l m u ta g e n e sis o f
triso m ic
(DES)
(BTT) s e e d
treated
(R am age 1965)
'6 3 - j- 1 8 -1 7 '
seed
f i e l d as t h e fe m a le rows in a c r o s s i n g b lo c k ,
parent.
in
1970 a n d
1971.
u nresponsive to g ra v ity
selectio n .
in th e
w ith 'A r i v a t 1 as t h e male
were
m ixed.
T h a t s e e d was grow n in t h e
com pletely
r o o t grow th
field
a t Bozeman in
1980 and
th e progeny of
one was g r a v i t r o p i c ,
a n d o n e was
T h is s e e d was f i e l d grow n and h a r v e s t e d as s i n g l e p l a n t s in
crosses
w ere
in
made
1982,
in
greenhouses, u t i l i z i n g seed from
the type of in h eritan c e,
agravitropic plants
g rav itro p ic
produced
revealed
w e re s e l f e d and h a r v e s t e d ;
agravitropic,
three se lfe d generations,
A ll
G erm ination t e s t s
i n t h e p r o g e n y o f a 1971 r a n d o m s i n g l e p l a n t
N ine s i n g l e p l a n t s
seven
was p l a n t e d
The
D i p l o i d f e m a l e p l a n t s w e re h a r v e s t e d and g ro w n o u t t w o s e l f e d
generations
1981.
( F i g u r e 4).
seed
p lan ts
seed
transplanted
to
the
sp ring
1984.
of
1984,
in
the
1983 h a r v e s t e d p l a n t s .
and g r a v i t r o p e s ,
from
the
Bozeman
To e v a l u a t e
in
the
s p e c if ic a lly A rivat,
a g r a v i t r o p i c population.
in
2. 8 9 mM g i b b e r e l l i c
was g e r m i n a t e d
pots
and
r e c i p r o c a l c r o s s e s w e r e made b e t w e e n s e l e c t e d
was g e r m i n a t e d
dormancy.
1983,
to
'B etzes',
A ll greenhouse
acid
to
overcome
observe root g raviresponse,
greenhouse.
F2
seed
and
was
then
sim ilarly
17
F ig u re 4.
O rig in o f th e a g r a v i t r o p i c b a r le y mutant.
number o f p l a n t s grown in s e l f - p o l l i n a t e d
a r e s h o w n f o r 1980 t h r o u g h 1984.
Th e p h e n o t y p e a n d
f ie ld populations
MANCHURIA mm2 X BONUS T 2 - 7 d
63-1-18-17
X ARIVAT
( D E S - t r e a t e d BIT)
1970
SINGLE PLANT
1971
SINGLE PLANT
AGRAVITROPES, GRAVITROPES, MIXED
1980, 1981
7
I
AGRAVITROPES, GRAVITROPES
1982
105
11
4
8
1983
473
73
21
52
1984
56
8
4
4
18
g e rm in a te d and s c o re d f o r r o o t g r a v ir e s p o n s e .1 A c h i - s q u a r e t e s t of
deviation
( L i t t l e and H i l l s
1978)
wa s u s e d i n a n a l y s i s o f t h e s e
as w e ll as th e o t h e r g e n e tic s s tu d ie s .
0.10 w e r e c o n s i d e r e d
P ro b ab ility
crosses
le v e ls le s s than
significant.
P o p u latio n A nalysis
Sodium d o d e c y l s u l f a t e
p o ly acry lam id e gel electrophoresis
PAGE) w a s u s e d t o c h a r a c t e r i z e t h e
th e
(SDS-
B and C h o r d e i n b a n d in g p a t t e r n s
a g ra v itro p ic . p o p u latio n .
The
h o rd e in
ex tractio n
of
and
e l e c t r o p h o r e s i s m ethods w ere a m o d i f i c a t i o n o f t h a t o f B lake e t a l.
(1982).
The d i s t a l h a l f o f s e e d s w e r e c r u s h e d w i t h p l i e r s and p l a c e d
i n 1 . 5 m l t u b e s w i t h 3 0 0 u I 55% ( v / v ) p r o p a n o l ,
a n d 2% ( v / v )
2-m ercaptoethanol.
Samples were in c u b a te d
h o u r , t h e n c e n t r i f u g e d a t 1 2 ,8 0 0 'g '
of supernatant
w ater,
was p l a c e d
200
ul
20%
(v/v)
m ercaptoethanol,
w ere
at
25% ( v / v )
'g' f o r
g ly cero l,
0.124
w ith
a t 60C f o r o n e
A 100 u l s a m p l e
300 u l d o u b l e d i s t i l l e d
P recipitated proteins
two
m inutes
M T ris-C l
were p e l l e t e d
and t h e n
d issolved
in
pH
2%
2-
6.8,
a n d 2% (w/ v) SDS i n a b o i l i n g w a t e r b a t h .
b i s a e r y lam ide g e ls a t
in
12,800
electro p h o resed
coom assie b l u e ,
f o r one m in u te .
in clean tubes
and r e f r i g e r a t e d o v e r n i g h t .
by c e n t r i f u g a t i o n
0 . 3 7 M T r i s - C l pH 8 . 8 ,
in
11.1%
15 mA p e r g e l .
30% ( v / v ) m e t h a n o l ,
m ethanol,
(w /v)
8% ( v / v )
(v/v)
The s a m p l e s
acry lam id e,
0.09%
(w /v)
G e l s w e r e s t a i n e d w i t h 0.1% (w/ v)
10% ( v / v ) a c e t i c a c i d
acetic
and d e s t a i n e d
acid.
The 1 9 8 0 / 1 9 8 1 a n d 1982 a g r a v i t r o p i c p o p u l a t i o n s w e r e c h a r a c t e r i z e d
for
B and
C h o rd e in
banding
p attern s.
Four seeds
a n a l y z e d and e a c h p l a n t was s c o r e d a s a h o m o zy g o te
p a r e n ta l banding p a tte r n )
or a heterozygote
per
plant
w ere
( f o u r s a m p le s o f one
(a h e t e r o z y g o u s b a n d i n g
19
p attern
or
both
paren tal
types).
P ercentage
hom ozygosity
due
to
i n b r e e d i n g was t e s t e d a g a i n s t e x p e c t e d v a l u e s f o r t h e p o p u l a t i o n .
Linkage A n a ly s is
C rosses
lethal
w ere
made b e t w e e n s e l e c t e d
tran slo catio n
tester
set
made w i t h e a c h t r a n s l o c a t i o n
m ale and fe m a le p a r e n t s .
(Table
as
w ithout com pletely
I) .
At
least
p lan ts
two
crosses
and a
were
l i n e and t r a n s l o c a t i o n l i n e s s e rv e d as
A ll
s e e d was g e r m i n a te d t o o b s e r v e r o o t
g r a v i r e s p o n s e and t r a n s p l a n t e d t o p o t s
plants
ag rav itro p ic
fe rtile
in th e greenhouse.
heads
were h a r v e s te d
At m a t u r i t y ,
and c l a s s i f i e d
sem isterile.
Table I.
T r a n s l o c a t i o n s , c h r o m o s o m a l b r e a k p o i n t s , and a u t h o r i t i e s f o r
th e b a rle y l e t h a l tr a n s lo c a tio n t e s t e r s e t used to determ ine
linkage to agravitropism .
T i-3 e,d
T l-S f, f
T l-6 a,c
T l-6e,a
T l-7k,c
T2-3a,b
T 2-4a,c
T2-4d,q
T 2-5a,v
T 3-4b,e
T3-7c , 3 - 7 d ,c
T4-7b,b
T 5-6b,I
L
L
Sat
S?
L
S?, S
P e r s s o n (1 970)
Ramage e t a l . (1961)
Ramage e t a l . (1 9 61 )
P e r s s o n ( 19 7 0 )
P e r s s o n (1970)
K a s h a a n d B ur nha m (1965)
S?, L
L ? , S?
Ramage e t a l . (1961)
Ramage e t a l . ( 19 6 1)
N i l a n (1964)
K a s h a a n d B ur nha m (1 965)
Ramage e t a l . (1961)
H a g b e r g e t a l . (1975)
Ramage e t a l . (1961)
-/ s
rH
I
U
r<
L,
S,.
S,
L,
L,
S, Li / L / S
S, S a t
L, L
S, S
a S = Short arm,
L = I o n g arm,
-=position not determined.
W henever p o s s i b le ,
seed lin g s
from
A uthority
Break P o i n t a
T ranslocation
each
Sat=Sate I lite,
?=probably in that arm,
f i v e a g r a v i t r o p i c and e l e v e n g r a v i t r o p i c F 2
sem isterile
F^
p lan t
w ere
tran sp lan ted
to
20
greenhouse benches.
follow ing equation
T h e s e p o p u l a t i o n s i z e s were d e t e r m in e d from t h e
(Sedcole
1977).
n = l o g (I-p)
l o g ( 1 - q)
The v a r i a b l e p i s t h e p r o b a b i l i t y o f f i n d i n g a t l e a s t o n e i n d i v i d u a l
w ith the d e s ire d t r a i t ,
trait,
q.
q is the p r o b a b ility o f th e occurance of the
an d n i s t h e s a m p l e s i z e r e q u i r e d by t h e c h o s e n v a l u e s f o r p and
A q
value
sem isterile
fe rtile
of
was
in d ividual
in d iv id u al
probability,
p,
used
fo r th e
in th e f e r t i l e
in
th e
p ro b ab ility
of
o btaining
a g r a v i t r o p i c c l a s s a n d 0.33 f o r a
sem isterile
t h e F2 p l a n t s
16 s e e d s
g ra v itro p ic
class.
The
were s c o r e d as f e r t i l e
or sem isterile.
from each F2 p l a n t w ere g e r m in a te d t o d e t e r m i n e t h e
genotype o f t h a t ' p la n t.
between a g r a v itro p is m
F2 s e g r e g a t i o n
ratio s
were t e s t e d
for
linkage
and t r a n s l o c a t i o n b r e a k p o i n t s .
Th e t r a n s l o c a t i o n
lines
used
in
th is
study have been backcrossed
to 'S c a s h a b e t', a c u I t i v a r w ith th e d o m in an t tw o-row head type.
agravitropic
plants,
a
w a s s e t a t 0. 9 9.
At m a t u r i t y ,
At l e a s t
0.67
population expresses the
recessive
s ix -ro w head type.
from t h e t r a n s l o c a t i o n c r o s s e s d e s c r i b e d above,
k e r n e l row s p e r s p i k e and e v a l u a t e d
chromosom e t w o and a g r a v i t r o p i s m .
The
F2
were sco red fo r
f o r l i n k a g e b e t w e e n t h e -V l o c u s on
C r o s s e s i n v o l v i n g a t r a n s l o c a t i o n on
chrom osom e tw o w ere n o t u sed in th e a n a l y s i s due t o a b e r r a n t r a t i o s
r e s u l t i n g from lin k a g e betw een th e t r a n s l o c a t i o n b r e a k p o i n t s
a nd t h e V
locus.
P lan ts
from
th e
1980/1981
p opulation
th at
w ere
id en tified
h e te ro z y g o u s f o r h o rd e in band in g p a t t e r n s w ere u t i l i z e d
linkage
study.
Th e
1 982 p r o g e n y o f
those
plants
as
a s F^ s i n a
would be e x p e c te d t o
21
segregate
one
homozygous
homozygous p a r e n t a l
type.
p aren tal
ty p e:
Independence o f
tw o
heterozygotes:
segregation
was
one
tested
for
t h e H o r - I a n d H o r - 2 l o c i on c h r o m o s o m e f i v e a n d a g r a v i t r o p i s m .
R e s u l t s and D i s c u s s i o n
G e n etic Stock
R eciprocal cro sses
com pletely g ra v itro p ic
three
gravitropes:
gravitropism
T a b le 2.
progeny.
one a g r a v i t r o p e ,
Fg s e g r e g a t i o n
indicating
fits
a ratio
monogenic c o n t r o l ,
co m p letely dom inant over a g ra v itro p is m
of
w ith
( T a b l e 2).
Fg s e g r e g a t i o n d a t a a n d c h i - s q u a r e v a l u e s f o r c r o s s e s b e t w e e n
t h e a g r a v i t r o p i c m u tan t and w i l d ty p e b a r l e y p l a n t s .
Grav.
Cross
rti
CM
I
X
X
X
X
X
O
(T i
I
CM
CM
Q
Betzes
67-1
A rivat
77-1
b e t w e e n a g r a v i t r o p e s and g r a v i t r o p e s y i e l d e d
for
3: I
P-VaIue
77
76
41
71
48
24
23
15
31
21
101
99
56
102
69
0.030
0.842
0.024
1.310
0.816
0.863
0.772
0.877
0.252
0.366
313
1 14
427
0.569
0.451
Betzes
116 -1
A rivat
92-6
Total
No. o f F2 P l a n t s
Agrav.
Total
a N um be r s r e f e r t o s i n g l e p l a n t s f r o m t h e 1983 a g r a v i t r o p i c p o p u l a t i o n .
bG r a v i t r o p e from t h e a g r a v i t r o p i c p o p u l a t i o n .
P opulation A nalysis
F ig u r e 4 shows t h e a p p e a ra n c e o f a p p a r e n t l y homozygous g r a v i t r o p i c
plan ts
in
1980/1981
and l a t e r
generations.
F oreign
c o n t a m i n a t i o n was c o n s i d e r e d a s a p o s s i b l e o r i g i n
d eterm in e
the o rig in
p opulation,
of the g ra v itro p ic p la n ts
SDS-PAGE c h a r a c t e r i z a t i o n
p a t t e r n s was u se d .
of
B and
seed or p o llen
of these p lants.'
in th e
To
ag rav itro p ic
C h o rd ein
banding
The H o r - 2 an d H o r - I l o c i e n c o d i n g t h e s e p r o t e i n s
22
are highly v a ria b le
studies
(D oll
id en tified
a n d may b e u s e d a s m a r k e r g e n e s i n e v o l u t i o n a r y
and
for
Brown
both
h e te ro z y g o u s progeny.
see d s examined.
1979).
p aren ts,
D istin ct
63-j-1 8 -1 7
banding
and
No o t h e r b a n d i n g p a t t e r n s
The h o r d e i n b a n d i n g p a t t e r n s
p attern s
A riv a t,
and
w ere
th eir
were found in th e
516
indicate a s im ila r origin
o f g r a v i t r o p e s and a g r a v i t r o p e s .
If
the
1971 p a r e n t p l a n t
was h e t e r o z y g o u s
a t th e Hor-I
and Hor-2
l o c i , th e. f o l l o w i n g s e l f e d g e n e r a t i o n would be e x p e c te d t o be o n e - h a l f
hom o zy g o tes and o n e - h a l f h e t e r o z y g o te s .
consist of th ree -fo rth s
The n e x t g e n e r a t i o n s h o u l d
h o m o z y g o te s and o n e - f o r t h h e t e r o z y g o t e s .
Chi-
\
square data
generations
p attern s
for segregation
agree
of
w ith
th ese
those
a t both
lo ci
expectations
generations
show
in the
1 9 8 0 / 1 9 8 1 an d 1982
(Table
3).
segregation
Hordein
banding
in d icativ e
of
a
p o p u l a t i o n in b re d from a s i n g l e h e te r o z y g o u s p l a n t .
Table 3.
R a tio o f hom ozygotes to h e te r o z y g o te s
h o r d e in b a n d in g p a t t e r n s in tw o in b re d
a g r a v itr o p ic population.
Homo.
1980/1981
B H ordeins
C H ordeins
1982
B Hordeins
C H ordeins
No. o f P l a n t s
T otal
H etero.
4
4
77
96
-
no u n a c c o u n t a b l e
hom ozygosity due t o
seed m ixture
X2 f o r
I:I
3:1
4
5
8
9
O
O
21
33
98
129
_
G ravitropic p la n ts are m o rp h o lo g ic a lly
W ith
f o r B and C b a r le y
g e n e ra tio n s of the
v ariatio n
in
in th e
sim ilar
there
is
P-Value
-
1.000
1.000
0.489
O
0.484
1.000
to
banding p a tte r n s ,
in b re e d in g as expected,
or co ntam ination
—
.
ag rav itro p es.
and p e r c e n t
no e v i d e n c e o f
a g r a v i t r o p i c population..
a
Thus,
23
the
grav itro p es
were
fo r use as c o n tro ls
deemed
su fficien tly
sim ilar
to
the
agravitropes
in p h y s io lo g ic a l s tu d ie s .
L in k a g e A n a l y s i s
S i x t y c r o s s e s w e r e made b e t w e e n
I) a n d a g r a v i t r o p i c p l a n t s .
of the
O n l y 40 s e m i s t e r i l e F 11S,
fourteen tra n s lo c a tio n s ,
S elfed
leth al
tran slo ca tio n
tran slo ca tio n
ca n n o t be
readily
fe rtile
heterozygotes
p r o b a b l y made w i t h
one
(Figure
determ ined
fe rtile
lines
(Table
co m p risin g seven
w e r e r e c o v e r e d f r o m 277 m a t u r e p l a n t s .
h etero zy g o tes:
s e m i s t e r l i e s : one
le th a l translocation
norm al
3).
segregate
hom ozygote,
F ertility
a t anthesis,
p lan ts
should
or
or
tw o
tw o
sem isterility
hence numerous c r o s s e s were
w hich d id
not have tr a n s lo c a te d
chromosomes.
Linkage
betw een
agravitropism
and a t r a n s l o c a t i o n
sh o u ld r e s u l t i n a l e t h a l homozygous g r a v i t r o p i c c l a s s ,
breakpoint
more th a n tw o -
t h i r d s s e m i s t e r i I e s in t h e h e t e r o z y g o u s g r a v i t r o p i c c l a s s , and more
than
o n e-th ird
reduction
fe rtile s
in
the
i n t h e homozygous g r a v i t r o p i c
tran slo ca tio n
sem isteriles:
crosses
(T able
one f e r t i l e
How ever,
sem isteriles,
each
which
represents
is
4).
class
In
not
the
gave
a
class
expected
5).
No
the
ra tio
of
tw o
t h r e e homozygous and t h r e e
sig n ifican t
g reater
(Figure
was fo u n d f o r any o f t h e
testin g
f o r each genotype,
heterozygous g r a v it r o p i c c l a s s e s
5).
ag rav itro p ic
number
aberrant
chi-squares
of
ratio
(T able
fe rtile s
w ith
than
linkage.
T h r e e o f t h e a g r a v i t r o p i c c l a s s e s g av e s i g n i f i c a n t c h i - s q u a r e s due t o a
g r e a t e r number o f f e r t i l e
plants,
as
d i f f e r e n t chromosomes a r e i m p l i c a t e d ,
these data
rem ain
inconclusive.
expected
w ith
linkage.
But,
six
so due t o t h e s m a l l sam p le s i z e s
24
F ig u r e 5.
D i a g r a m m a t i c r e p r e s e n t a t i o n o f Fg s e g r e g a t i o n w i t h l i n k a g e
b e t w e e n a g r a v i t r o p i s m and a l e t h a l t r a n s l o c a t i o n b r e a k p o i n t
(G d e n o t e s d o m i n a n t g r a v i t r o p i s m a l l e l e a n d g d e n o t e s
recessive agravitropism a l l e l e ) .
G
i G
g
.........
g
I ie n illlllllM l^ lllM e e * " * *
IU IIIIIIM IH M ^ M M IM M M M
.............................................. ............... .
.................................................. >•••
TRANSLOCATION HETEROZYGOTE
AGRAVITROPE
WITH LETHAL GENE
'
f
g
#
2
'
G
I G
F,
.... •••••.....
#111111
I SEMISTERILE GRAVITROPE
:
1 FERTILE GRAVITROPE
>r
I G
g
g
I G
I G
g
11 M i l l M M M l I l # M M
I
lM M H H IM H IM # M M M * ^ e e e e i
I LETHAL
2 SEMISTERILE
GRAVITROPE
GRAVITROPES
.
I FERTILE
AGRAVITROPE
25
T a b le 4.
F 2 s e g r e g a t i o n d a t a and c h i - s q u a r e v a l u e s f o r homozygousg r a v i t r o p e s t o h e te r o z y g o u s g r a v i t r o p e s from c r o s s e s betw een
t h e a g r a v i t r o p i c b a r l e y m u t a n t and t h e l e t h a l t r a n s l o c a t i o n
te ste r set.
type
of
translocations
m u tatio n
is
sem isterile:
ratio
leth al
not
1981).
fu n ctio n in g ,
one f e r t i l e .
is
und eterm in ed
expected
w ith s ig n if ic a n t
many o f t h e
th at
the
F2 segregation
T estin g each g r a v itr o p ic
two c r o s s e s
0.348
0.483
1.000
0.571
0.169
0.707
0.276
for
With t h e a s su m p tio n
the
P-Value
Q.' 880
0.491
0
0.321
1.893
0 . 141
1.185-
67
35
24
72
56
19
18
.
m u tatio n
(B iggerstaff
yielded
again,
49
21
16
51
32
14
11
18
14
8
21
24
5
7
T l-6 a,c
T2-3a,b
T2-5a,v
T3-7c, 3 -7 d ,c
T4-7b,b
T 5-6b,I
T6-7c, I
The
X2 f o r '
1:2
N o . o f F2 G r a v . ' P l a n t s
Total
H etero.
Homo.
T ran slocation
genotype
chi-squares
leth al
is
one
for th is
( T a b l e 5).
both cases e x h ib it seg re g a tio n o p p o site o f th e expected
But
linkage
ratio s.
Hanson
and
K ram er
reco m b in atio n
th at
tran slo catio n
crosses.
presented here is
d etect
linkage
translocation
four,
(1950)
can be d e te c te d
The a v e r a g e
58 p l a n t s ,
w ith in
lines
present
used
for
a given
th e
percentage
number o f
F2 p o p u latio n
for
the
F2's
in
crosses
w h ic h w o u ld p r o v i d e enough i n f o r m a t i o n t o
15 m a p u n i t s
in
from
tab les
these
of
crosses
th e
breakpoint.
test
chromosomes
and f i v e w ith o n ly one o r tw o b r e a k p o i n t s
map u n i t s f r o m o n e o r t w o c h r o m o s o m a l l o c a t i o n s
The s e v e n
( F i g u r e 6).
leaves
a
one,
two,
F ifteen
la r g e amount
o f t h e b a r l e y genome u n e x a m i n e d f o r l i n k a g e t o a g r a v i t r o p i s m .
26
T a b l e 5.
F2 s e g r e g a t i o n d a t a and c h i - s q u a r e v a l u e s f o r s e m i s t e r i l i t y
to f e r t i l i t y in r e l a t i o n t o g r a v it r o p i c genotype fo r c ro sse s
b e tw e e n t h e a g r a v i t r o p i c b a r l e y m u ta n t and th e l e t h a l
tra n s lo c a tio n t e s t e r set.
Homozygous G r a v i t r o p e s
T ran slocation
T l-6 a,c
T 2-3a,b
T2-5a, v
T 3 -7 c,3 -7 d ,c
T 4-7b,b
T6-7c, I
N o . o f F2 P l a n t s
s s . a F ert.
Total
7
7
4
11
8
2
11
7
4
10
16
5
18
14
8
21
24
7
X2 f o r
2:1
5.225
1 . 142
0.518
1.423
10.830
3.099
P-Value
0.022*
0.285
0.518
0.233
0 . 001*
0.078*
X2 f o r
I:I
P-VaIue
0.500
0
0
0
2.042
0.571
0.480
1.000
1.000
1.000
0.153
0.450
X2 f o r
'I : I
P-VaIue
H eterozygous G r a v itr o p e s
T ranslocation
H
I
O
n3
(Ti
T l-6 a,c
T2-3a,b
T 2-5a,v
T3-7c, 3 -7 d ,c
T 4-7b,b
T 5-6b,I
N o . o f F2 P l a n t s
F e r t . Total
SS.
18
12
8
23
14
6
5
31
9
8
28
18
8
6
49
21
16
51
32
14
11
X2 f o r
2:1
18.950
0.531
1.393
10.100
6.807
2.680
1.438
P-Value
0.000*
0.466
0.238
0.001*
0.009*
0.102
0.230
2.939
0.196
0
0.314
0.281
0.071
0
0.086*
0.662
1.000
0.575
0.596
0.789
1.000
X2 f o r
I:I
P-Value
Homozygous A g r a v i t r o p e s
T ranslocation
T l-6 a,c
T2-3a,b
T2-5a,v
T3-7c, 3-7d,c
T 4-7b,b
T 5-6b,I
T6-7c, I
N o . o f F2 P l a n t s
SS.
F e r t . Total
X2 f o r
2:1
16
9
4
11
18
4
5
3.449
0
7.693
6.097
0
0.418
0
16
3
10
15
8
4
2
32
12
14
26
26
8
7
aSS.= s e m is te r ile , F e r t . = f e r t i l e .
5ltS i g n i f l e a n t a t a p r o b a b i l i t y l e v e l o f 0 . 1 0 .
P-Value
0 . 063*
1.000
0.006*
0.014*
1.000
0.518
1.000
0
2.083
1.786
0.346
3.115
0
0.571
1.000
0.149
0.181
0.556
0.078*
1.000
0.450
27
F ig u re 6.
D i a g r a m m a t i c r e p r e s e n t a t i o n o f chromosome seg m e n ts o f t h e
b a r l e y genome t e s t e d by c r o s s e s b e tw e e n th e a g r a v i t r o p i c
m u ta n t and t h e l e t h a l t r a n s l o c a t i o n t e s t e r s e t , and H o r - I ,
H or-2,
a n d V m a r k e r g e n e s (S = s h o r t a r m ,
L= l o n g a r m ,
S at= S atellite)..
Tl-6a
I S -------------------------------------------O-
L
T2-3a
2S ------------------------------- :------O
V
T2-5a
------------------------------- L
T 2 -3 a , T3-7c
3S ------------------:--------------------O
T3-7d
------------------ ,-------- L
T4-7b
4S -------------------------------------- O
L
TS-Gb
H or-I , 2
T2-5a
5S -------------------------------------- O
Tl-Ga
G S a t -------------
TS-Gb
T G- 7 c.
--------------------------------—O
S p e c ific m arker t r a i t s
b a r l e y chromosomes.
L
T3-7c
--------------------------- L
T 3-7d, T6-7c
------------------------------ O
T4-7b
7 S a t ------------
L
w e re u s e d t o f u r t h e r e x p l o r e some o f t h e
Linkage betw een k e r n e l rows p e r s p ik e ,
b y t h e V l o c u s on c h r o m o s o m e t w o , a n d a g r a v i t r o p i s m
plants
showed
from
no
the
sig n ifican t
segregation
1980/1981
ra tio .
Therefore,
at
the
crosses
d ifferences
The
g en eratio n
agravitropism
differences
tran slo catio n
progeny
w ere
Hor-I
(Table
from
of
the
w a s e x a m i n e d i n Fg
C hi-square
ex p ected
heterozygous
sim ilarly
and H o r-2
6).
loci
an aly zed
(Table
for
7).
is
no
evidence
of
lin k a g e betw een th e
analysis
th ree:o n e
p lan ts
from
lin k ag e
the
to
No s i g n i f i c a n t
from t h e e x p e c te d one:tw o:one s e g r e g a t i o n r a t i o
there
controlled
w ere found.
agravitropism
g e n e a n d t h e H o r - I o r H o r - 2 l o c i on t h e s h o r t arm o f c h r o m o s o m e f i v e ,
o r t h e V l o c u s on t h e
l o n g arm o f chrom osom e two.
28
T ab le 6.
F2 s e g r e g a t i o n d a ta and c h i - s q u a r e v a lu e s f o r num ber o f
k e r n e l row s p e r s p ik e in r e l a t i o n to a g r a v i t r o p i s m from
c r o s s e s b e tw e e n t h e a g r a v i t r o p i c b a r l e y m u ta n t and t h e l e t h a l
tra n s lo c a tio n t e s t e r set.
N o . o f F2 P l a n t s
2-row
6-row
Total
A gravitropes
■G r a v i t r o p e s
T a b l e 7.
72
180
34
62
X2 f o r
3: I
106
242
B H ordeins
A gravitropes
G ravitropes
C Hordeins
. A gravitropes
G ravitropes
No . o f F2 P l a n t s
Aj A2
Total
A2A2
X2 f o r
1:2:1
The g e n e t i c
agravitropism
tested.
P-VaIue
10
5
9
12
8
5
27
22
3.296
0.182
0.190
0.913
13
6
20
13
7
4
40
23
I .800
0.739
0.409
0.697
aA jA ^= A rivat b a n d in g p a t t e r n , A jA g=H eterozygous
AgAg=GS^-IS-IV ban d in g p a t t e r n .
an aly ses
provided
banding
no s i g n i f i c a n t
and any o f t h e t r a n s l o c a t i o n
pattern,
lin k a g e betw een
b reakpoints
o r m arkers
Th e l o n g a r m s o f c h r o m o s o m e s o n e a n d f o u r w e r e n o t t e s t e d ,
s h o r t a rm s w ere t e s t e d by o n ly one b r e a k p o i n t
but
0.116
0.882
'2.465
0.022
Fg s e g r e g a t i o n d a t a a n d c h i - s q u a r e v a l u e s f o r t h e B a n d C
b a r le y h o rd e in banding p a t t e r n s in r e l a t i o n t o a g ra v itro p ism '
fro m s e l f ed a g r a v i t r o p i c and g r a v i t r o p i c h e t e r o z y g o u s p l a n t s .
AjAja
five
P-Value
(F ig u re 6).
and
The o t h e r
chromosomes were examined f o r lin k a g e a t t h r e e o r f o u r p o s itio n s ,'
data
from
chromosom e
the
six
Chrom osom es one,
b arley
stu d ies
are
agravitropism .
order
arm
weak
four,
chrom osom es,
in
long
due
chromosom e
to
th e
and s i x w ere t h e
but a ll
to
of
should
d eterm in e
sm all
fiv e
Fg
both
p o p u latio n
arms
of
sizes.
l e a s t e x p lo re d of the seven
be ex a m in e d
th e
and
in
fu rth e r
chrom osom al
linkage
lo catio n
of
29
AGRAVI TROPI C ROOT RESPONSE
M a t e r i a l s and Methods
A q r a v i t r o p i c Growth
In
lines,
all
experim ents,
g ravitropes
A r i v a t and 6 3 - j - 1 8 - 1 7 ,
plan ts
from
the
as w e ll as
1983 a g r a v i t r o p i c
randomly s e l e c t e d
were
single plants
(L ittle
and H i l l s
randomly s e l e c t e d
population.
from t h e
b etw e en a g r a v i t r o p e s and g r a v i t r o p e s
variance
1978).
r e p r e s e n t e d by th e
parental
g ravitropic
A ll a g r a v i t r o p e s were
1983 p o p u l a t i o n .
D ifferences
w ere e v a l u a t e d by a n a l y s i s o f
P robability
l e v e l s g r e a t e r t h a n 0. 0 5
were c o n s id e r e d i n s i g n i f i c a n t .
A g ra v itr o p e s w ere com pared to g r a v it r o p e s f o r g r a v ! r e s p o n s e in
lig h t
and d a r k .
treatm ents;
light,
T w elve
a g ra v itro p e s in continuous
agravitropes
darkness,
rep licatio n s
in
g ra v ic u rv atu re
light,
com plete darkness,
A fte r'4 8 h ours,
was
recorded
R oot c u r v a t u r e was e s t i m a t e d
least
seeds
for
gravitropes
and g r a v i t r o p e s
the
four
in continuous
in
com plete
eleven
roots.
r o o ts w ere o r ie n te d h o r i z o n t a l l y
a f t e r o n e , tw o,
E longation
rates
of
four,
w ith a p r o tr a c to r to
S eedlings
24 h o u r s a n d s h o o t g r a v i c u r v a t u r e
com pared.
th ree
were g e r m in a te d in v e r t i c a l l y o r i e n t e d c y l i n d e r s o f m o iste n e d
f i l t e r paper.
on a t
of
f i l t e r p a p e r in c o n s ta n t l i g h t .
and e i g h t h o u rs .
w ithin
five
degrees
m aintained h o riz o n ta lly
for
was r e c o r d e d .
agravitropic
F ive r e p l i c a t i o n s
were
and
and g r a v i t r o p i c
o f 50 s e e d s
roots
were a ls o
w e re p l a c e d on m o i s t e n e d
Number o f r o o t s and r o o t g ro w th p e r
30
seedling
(mm)
were
each r e p l i c a t i o n ,
recorded
24 ,
for
the
five
f a s t e s t grow ing se e d lin g s
30 a n d 42 h o u r s a f t e r
in
im bibition.
Root Tip S ta r c h C ontent
S tarch co n ten t
(nanomoles o f anhydrous g lu c o s e e q u i v a l e n t s )
p r o t e i n w a s d e t e r m i n e d f o r 66 a g r a v i t r o p i c
sam ples
usin g
method.
E a c h s a m p l e c o n s i s t e d o f 20 I mm p r i m a r y r o o t t i p s ,
in
a glass
a
m o d ificatio n
tissue
was
a t . 3 29 0 ' g'
removed,
e t h a n o l was ad d e d ,
f o r 20 h o u r s .
the
O utlaw
and
h o m o g e n i z e r w i t h 3 ml c o l d ,
F ollow ing c e n tr if u g a tio n
supernatant
of
a n d 47 g r a v i t r o p i c
200 u l
and t u b e s
0.4
M potassium
w ith
(1979)
disrupted
double d i s t i l l e d
were capped t i g h t l y
Samples were n e u t r a l i z e d
root tip
M anchester
f o r 30 m i n u t e s ,
p e r ug
w ater.
a l l b u t 200 u l
hydroxide,
and
incubated
of
0.2
at
M
90C
200 u l 0 . 4 M h y d r o c h l o r i c
a c i d , t h e n 0 . 4 u n i t s o f a m y l o g l u c o s i d a s e i n 1 0 0 mM s o d i u m a c e t a t e pH
4. 4 w a s a d d e d .
F ollow ing in cu b atio n
were c e n tr i f u g e d a t
at
5 SC f o r t w o h o u r s ,
3 2 9 0 ' g' f o r 30 m i n u t e s ,
was t r a n s f e r e d t o c l e a n t u b e s .
and' 8 0 0 u l o f
At room t e m p e r a t u r e ,
th e sam ples
supernatant
I ml o f g lu c o s e
r e a g e n t c o n t a i n i n g 0.5 u n i t s g l u c o s e - 6 - p h o s p h a t e d e h y d r o g e n a s e ,
u n i t s hexokinase,
adenine
10 mM a d e n o s i n e t r i p h o s p h a t e
din u cleo tid e
phosphate
(ATP),
0.8
2 mM n i c o t i n a m i d e
(NADP), 3 6 mM d i t h i o t h r e i t o I ,
2 mM
m a g n e s i u m c h l o r i d e a n d 360 mM T r i s - C l pH 8. 8 w a s a d d e d a n d a l l o w e d t o
react
for
30
m in u tes.
dehydrogenation
absorbance a t
starch
red u ctio n
of
NADP t o
NADPH d u r i n g
o f g l u c o s e - 6 - p h o s p h a t e was m e a s u r e d a s t h e ch a n g e in
3 4 0 nm.
stan d ard s
M a n c h e s t e r 1979).
d eterm in ed
The
u sin g
was
A r e g r e s s i o n e q u a tio n d e v e lo p e d from p o ta to
used
to
estim ate
to tal
starch
P r o t e i n c o n t e n t o f t h e 20 I mm r o o t t i p
th e
Lowry
et
a I.
( 19 5 1 )
p ro tein
(O utlaw
and
sam ples
was
assay
w ith
31
p re cip ita tio n
by t r i c h l o r o a c e t i c
acid
A ir dry w eights o f fo u r a g ra v itro p e
I mm r o o t t i p s
( B e n s a d o u n a n d W e i n s t e i n 1976).
and f o u r g r a v i t r o p e
s a m p l e s o f 500
w e r e d e t e r m i n e d and raw d a t a a d j u s t e d t o c o m p e n s a t e f o r
t h e 8% w e i g h t d i f f e r e n c e b e t w e e n a g r a v i t r o p e s a n d g r a v i t r o p e s .
Exogenous Auxin S e n s i t i v i t y
Auxin s e n s i t i v i t y
to tal
ro o t grow th
of six
in
ag rav itro p ic
auxin tre a tm e n ts .
in
prim ary
varying
concentrations.
Four
rep licatio n s
The s e e d s w e re g e r m i n a t e d b e tw e e n tw o s h e e t s o f
10 mM p o t a s s i u m n i t r a t e
NAA i n c o n c e n t r a t i o n s o f 0 ,
1 0 0 u M , 5 0 0 u M , a n d I mM.
seedlings
of
D ata
expressed
are
auxin
was e x a m in e d a s a f u n c t i o n o f
and s i x g r a v i t r o p i c s e e d s w ere u s e d f o r th e t e n
f i l t e r p ap e r m oistened w ith
the
roots
six
averaged over four
10 n M ,
I uM,
5 uM,
A f t e r 48 h o u r s , t h e t h r e e
germ inated
as
10 0 nM,
a n d IAA,
were
a percent
measured
of
control
for
2,4-D ,
or
10 u M , 50 uM,
m ost elongated
to tal
(no a u x i n )
root
growth.
ro o t grow th
rep lications.
Endogenous Auxin C o n t e n t
■Root e n d o g e n o u s IAA c o n t e n t s w e r e m e a s u r e d u s i n g a m o d i f i c a t i o n o f
th e m ethod o f L iu and T i l l b e r g
g rav itro p e cross,
ag rav itro p ic
hypochlorite
in
p h otolabile,
tim es.
F 2 see d from an a g r a v i t r o p e X
p a r e n t a l s e e d , a n d s e e d f r o m 12 g r a v i t r o p i c a n d 13
p lan ts
w ere
surface
sterilized
and g e r m i n a t e d on m o i s t b l o t t e r
0.5 g f r e s h w e i g h t
p estel
(1983).
8
ml
w ith
paper.
20%
A fter
(FW) r o o t s a m p l e s w e r e g r o u n d w i t h
80%
therefore
(v/v)
root
m ethanol.
sam ples
(v/v)
from
fo u r days,
a m o r t a r and
In d o le-3-acetic
were p r o te c te d
sodium
acid
light
at
is
all
E x t r a c t i o n o f IAA f r o m t h e r o o t t i s s u e w a s b y g e n t l e s h a k i n g
32
for
20 h o u r s
potassium
at
SC:
V olum es
phosphate a c id if ie d
w ere
brought
to
100
ml
w ith
0.75
M
t o pH 2 . 7 w i t h 2 . 8 M p h o s p h o r i c a c i d .
D i e t h y l e t h e r w i t h 0.01% (w/ v) b u t y l a t e d h y d r o x y t o l u l e n e w a s l a y e r e d on
th e r o o t homogenate,
to
a n d 1 50 x 32 mm c e l l u l o s e d i a l y s i s
14,000 m o l e c u l a r w e ig h t c u t o f f )
containing
tubing
(12,000
15 m l 0. IM p o t a s s i u m
p h o s p h a t e pH 9 . 0 w a s s u s p e n d e d i n t h e e t h e r .
P artitio n in g of
the
f o r t h r e e h o u r s a t room
r o o t h o m o g e n a te was by g e n t l e
tem perature.
pH w a s
Th e s a m p l e s w e r e r e m o v e d f r o m t h e d i a l y s i s t u b i n g a n d t h e
read ju sted
cartridges
stirrin g
IAA f r o m
to
2.7.
W aters
Sep-pak
C18 s a m p l e p r e p a r a t i o n
were used t o f u r t h e r p u r i f y t h e s o l u t i o n s .
E l u t a n t from th e
c a r t r i d g e s was e v a p o r a t e d t o d r y n e s s u n d e r a s t r e a m o f n i t r o g e n and
r e d i s s o l v e d i n 50 u l m e t h a n o l .
High p e r f o r m a n c e l i q u i d c h r o m a to g r a p h y
a n d q u a n t i f y IAA i n t h e s a m p l e s .
colum n
was
a c eto n itrile
used
in
w ith
a
fiv e
(HPLC) w a s u s e d t o s e p a r a t e
A 4 x 12 5 mm, 5 urn E. M. S c i e n c e C I S
m inute
g rad ien t
0.1% ( v / v ) a c e t i c a c i d .
I AA
elu tin g
IAA e l u t e d
from
th e
from
colum n
the
was
5
to
20%
(v/v)
S t a n d a r d IAA w a s a d d e d t o
s a m p l e s t o i d e n t i f y t h e IAA p e a k r e t e n t i o n t i m e .
ml p er m inute,
of
colum n a t
d etected
A t a f l o w r a t e o f 1.5
1 2 . 8 5 _+ 0 . 0 7 m i n u t e s .
by
a
s p e c t r o p h o t o m e t e r w i t h e x c i t a t i o n a t 220 nm a n d e m i s s i o n
flu o rescen ce
up t o
320 nm.
K n o w n a m o u n t s o f IAA w e r e u s e d t o d e v e l o p a r e g r e s s i o n e q u a t i o n f o r
p ea k h e i g h t and c o n c e n t r a t i o n .
using
isotope d ilu tio n .
T o t a l IAA p e r s a m p l e w a s d e t e r m i n e d
33
R e s u l t s and D i s c u s s i o n
A q r a v i t r o p i c Growth
The a g r a v i t r o p e w a s i n i t i a l l y
response.
F ollow ing
a g ra v itro p e 's
roots
determ ined a f t e r
g rav itro p ism .
plants
were
g rav istim u latio n
had n o t curved
24 h o u r s
and
found betw een
1961;
lig h t
(Table
all
Root g r a v it r o p i c
( La ke a n d S l a c k
T a b le 8.
exam ined f o r ev idence o f g r a v i t r o p i c
shoots
f o r up t o
eig h t
hours,
the
8). ■ S h o o t g r a v i r e s p o u s e
was
displayed
response is
com plete
negative
l i g h t d e p e n d e n t in some
W i l k i n s a n d Wa in 1 97 4) ,
b u t no d i f f e r e n c e s
and d a r k g ro w n s e e d l i n g s
in t h i s
experim ent.
D egrees o f c u r v a t u r e o f l i g h t and d a rk grow n r o o t s o f th e
a g r a v i t r o p i c b a r l e y m u ta n t and g r a v i t r o p i c s e e d l i n g s a t fo u r
tim e in te rv a ls follow ing g ra v istim u la tio n .
A gravitropes
L ight
Dark
G ravitropes
L ight
Dark
I h
2 h
4 h
8 h
0
0
0
0
0
0
0
0
32 + 2a
37 + 2
48 _+' 2
55 + 3
71 + 2
71 + 3
80 + 2
74 + 3
a S a m p l e mean _+ s t a n d a r d e r r o r .
T otal
root
grow th
was
a g r a v i t r o p e s and g r a v i t r o p e s
had
sig n ifican tly
few er
not
sig n ifican tly
(T a b le 9).
roots
and
A g r a v i t r o p i c p ea (O lsen and I v e r s e n
A rab id o p sis
(M aher and M a r t i n d a l e
d ifferen t
Y et, a g r a v itro p ic se e d lin g s
g reater
1980a),
elongation
m aize
(Pi l e t
that
the
increased
in h ib ito r in the roots.
per
root.
1983), and
198 0) m u t a n t s a l s o d i s p l a y g r e a t e r
ro o t elongation, ra te s than th e ir g ra v itro p ic c o n tro ls.
suggests
betw een
elongation
P ile t
(1983)
may b e d u e t o a l a c k o f g r o w t h
T h a t g r o w t h i n h i b i t o r may a l s o b e r e q u i r e d f o r
34
d i f f e r e n t i a l ’g r o w t h a n d g r a y i c u r v a t u r e .
A bscisic ac id
ethylene
ro o t grow th
( C h a d w i c k a n d •B u r g
p o ssib le ro les
in g r a v ic u r v a tu r e .
(Chadwick an d Burg 1967),
also
cause
suggest
are
sen sitiv ity
a
low er
may
in h ib ito rs
a nd
w ith
so low er endogenous auxin c o n c e n tr a tio n s
endogenous
account
A rabidopsis a g r a v itro p ic
1975)
A uxins in d u ce e th y le n e s y n t h e s i s
l e s s e t h y l e n e to' be p ro d u c e d .
th at
Table 9.
1967)
(P ilet
for
th e
M irza e t a l.
auxin
(1984) s i m i l a r l y
co n cen tratio n
g reater
root
may
or
elo n g atio n
altered
in
the
m utants.
T o t a l r o o t g r o w th , r o o t s p e r s e e d l i n g , and l e n g t h p e r r o o t a t
th ree
tim e
in terv a ls
fo llo w in g
im b ib itio n
fo r th e
a g r a v i t r o p i c b a r l e y m u ta n t and g r a v i t r o p i c s e e d l i n g s .
24 h o u r s
A gravitropes
G ravitropes
hours
A gravitropes
G ravitropes
hours
r
A gravitropes
G ravitropes
T otal root
g r o w t h (cm)
Roots p e r
seedling
0 . 5 8 + . 10
0 . 5 5 + .07
1 .6 0 + .19
2.25 + . 21*
0.22
2 . 7 8 + .15
3 . 3 1 _+ . 15*
0 . 5 8 _+ . 0 4
0 . 5 1 + . 03
3 .3 7 + .19
4 . 3 1 _+ . 1 8 * *
1.36 + .06
1 .12 + .06**
1 . 6 3 + . 14
1 . 7 1 + . 14
•
4 . 5 9 + .32
4 . 9 4 + .32
Length p e r
r o o t (cm)
0.34 + .04
+ .02*
^ S ig n ific a n t a t a p r o b a b ility le v e l of 0.05.
* * S ig n ifle a n t a t a p r o b a b ility lev el of 0.01.
Root Tip S ta r c h C ontent
Root
tip
starch
contents
w ere
com pared
for
agravitropes
and
g r a v it r o p e s to i n v e s t i g a t e th e m u ta n t's a b i l i t y to p e r c ie v e g r a v ity .
S tarch
in
the
( I v e r s e n 1 96 9 ).
the c o le o p tile ,
root
cap
am yloplasts
is
req u ired
for
g rav iresp o n se
An a m y l o m a i z e m u t a n t w h i c h h a s s m a l l e r a m y l o p l a s t s
in
also d isp la y s decreased g ra v iresp o n se (H ertel e t al.
35
1969).
No s i g n i f i c a n t d i f f e r e n c e s
gravitropic
T a b l e 1 0.
root t i p
starch
were found betw een a g r a v i t r o p i c
contents
A gravitropes
G ravitropes
M icro sco p ic
num ber,
g ra v itro p ic
w e ll w ith
starch
10).
S t a r c h c o n t e n t (nm a n h y d r o u s g l u c o s e e q u i v a l e n t s ) p e r u g
p r o t e i n o f 2 0 Imm r o o t t i p s a m p l e s f o r t h e a g r a v i t r o p i c
b a r l e y m u t a n t and g r a v i t r o p i c s e e d l i n g s .
nm A n h y d r o u s g l u c o s e e q u i v a l e n t s
p e r ug p r o t e i n
No. o f
samples
size,
(Table
or
in v estig atio n s
y i e l d e d n o d i f f e r e n c e s i n amy l o p l a s t
sed im en tatio n
root tip
the
0.552 + .024
0 .5 5 4 + .028
66
47
colum ella
sim ilarity
contents.
Moore
ra te
b etw een
c e lls
in g r a v itr o p ic
(1985)
also
ER i s
colum ella
found
cell
in
a cup-shaped
(O lsen and
noted
no d i f f e r e n c e s
1980b).
o f ER.
at
and
This corresponds
and a g r a v i t r o p i c
aggregation
Iversen
ag rav itro p ic
( M o o r e 1985).
colu m ella o r g a n e lle s ," in clu d in g the d i s t r i b u ti o n
the
and
root tip
in o t h e r
In pea
th e bottom
An a g r a v i t r o p i c
roots,
of each
pea
m utant
h a s n o rm a l a m y l o p l a s t m ovem ent and c o l u m e l l a c e l l u l t r a s t r u c t u r e ,
e x c e p t t h a t t h e ER i s n o t a g g r e g a t e d .
be
in terferin g
G ravitropic
w ith
th e
This
m u ta n t's
and a g r a v i t r o p i c
b arley
r a n d o m ER d i s t r i b u t i o n
a b ility
root
to
colum ella
o r i e n t e d a d j a c e n t and p a r a l l e l t o t h e c e l l w a l l s ,
d id n o t change w ith g r a v i s t i m u l a t i o n .
is
Thus,
perceive
cells
may
g rav ity .
displayed
ER
and t h a t d i s t r i b u t i o n
a n a l t e r e d ER d i s t r i b u t i o n
n o t e v id e n t in t h i s b a r le y m utant.
E q u iv a le n t amounts o f s t a r c h
in th e
root tip s,
and no d i f f e r e n c e s
1
in
cellu lar
th at
th is
morphology betw een g r a v i t r o p e s
m u tatio n
is.n o t
sim ilar
to
and a g r a v i t r o p e s ,
other
indicate
known g r a v ! p e r c e p t i o n
36
m utants.
T his
ag rav itro p ic
apparatus
(sed im en tin g ,
m utant
appears
starch -filled
to
have
am yloplasts)
th e
to
req u ired
p erceive
a
gravistim ulus.
Exogenous Auxin S e n s i t i v i t y
Increasing
c o n c e n t r a t i o n s o f NAA,
seedlings in h ib ite d
grow th
ro o t elongation.
was s i m i l a r
2,4-Q ,
o r IAA a p p l i e d t o b a r l e y
■G r a v i t r o p i c a n d a g r a v i t r o p i c
w h e n NAA w a s a p p l i e d
(F igure
7).
root
A g rav itro p es
t r e a t e d w i t h 2 , 4 - D h a d f a s t e r g r o w t h t h a n g r a v i t r o p e s a t t h e 5 x IO- ^ M
treatm ent,
b u t s i m i l a r grow th r a te s a t o th e r c o n c e n tra tio n s
C onversely,
IAA t r e a t m e n t s y i e l d e d h i g h l y
a g r a v i t r o p i c and g r a v i t r o p i c
IAA ( F i g u r e 9).
IAA,
sig n ific a n t d ifferen ces
in
r o o t g r o w t h r a t e s b e t w e e n 10~^ M t o IO- ^ M
The a g r a v i t r o p e ' s
grow th
response
is
more t o l e r a n t
of
b u t s i m i l a r t o 2 , 4 - D a n d NAA t r e a t m e n t s o f g r a v i t r o p e s .
Tolerance to
S ta ffo rd
a u x in s has been r e p o r te d
e t ' a I.
G erm in atio n
in
1968),
IAA
including
and
2,4-D
A rabidopsis th a l i a n a m utants
w ere
id en tified
auxins.
Those
the
b arley
(D erscheid
so lu tio n s
by a
lack
of
m utants
also
exhibit
A rabidopsis
f o r many p l a n t
yielded
( Ma h e r a n d M a r t i n d a l e
g re a te r elo ngation per root,
But,
( F i g u r e 8).
m utants
root
grow th
much l i k e
are
et
a I.
auxin
19 8 0 ) .
in h ib itio n
com pletely
species
The m u t a n t s
w ith
agravitropic
tolerant
1952).
to leran t
applied
roots
the barley a g ra v itro p ic
eq u ally
(see
of applied
and
m utant.
IAA a n d
2,4-D.
Andreae
applications
treated
(Andreae
(1967)
o f IAA,
w ith
1967)
found pea r o o t g ro w th i n h i b i t i o n t o be s i m i l a r w ith
NAA,
o r 2,4-D.
F ollow ing auxin tr e a tm e n t,
IAA o r -NAA r e c o v e r e d
and was a f f e c t e d
less
fa ste r
from
s e v e r Iy
grow th
(Ingensiep
tissue
in h ib itio n
1982)
than
37
F i g u r e 7.
I n h i b i t i o n o f b a r l e y r o o t g r o w t h f o r a g r a v i t r o p e s and g r a v i t r o p e s w i t h i n c r e a s i n g c o n c e n t r a t i o n s o f NAA.
T reatm ent
means + s t a n d a r d ^ r r o r s a r e e x p r e s s e d a s p e r c e n t o f c o n t r o l .
• AQRAVITROPE
oQRAVI TROPE
M NAA
F ig u r e 8.
I n h i b i t i o n o f b a r l e y r o o t g r o w th f o r a g r a v i t r o p e s and g r a v i t ropes w ith in c re a sin g c o n c e n tr a tio n s o f 2,4-D .
T reatm ent
m e a n s _+ s t a n d a r d e r r o r s a r e e x p r e s s e d a s p e r c e n t o f c o n t r o l .
* AQRAVITROPE
o QRAVITROPE
M 2,4-D
38
2 , /I-D t r e a t e d
tissu e.
the
of
a b ility
th e
Congugation e s s e n t i a l l y
R o o t g r o w t h a p p e a r s t o be h i g h l y d e p e n d e n t on
tissu e
to
m etab o lize
accu m u lated
auxins.
i n a c t i v a t e s a n d i m m o b i l i z e s e x c e s s IAA a n d NAA,
w h i l e 2 , 4-D g e n e r a l l y r e m a i n s u n c o n g u g a t e d and m o b i l e i n t h e t i s s u e
(Ingensiep
F i g u r e 9.
1982).
I n h i b i t i o n o f b a r l e y r o o t g ro w th f o r a g r a v i t r o p e s and g r a v i t r o p e s w i t h i n c r e a s i n g c o n c e n t r a t i o n s o f IAA.
T reatm ent
m e a n s _+ s t a n d a r d e r r o r a r e e x p r e s s e d a s p e r c e n t o f c o n t r o l .
• AORAVITROPE
o QRAVITROPE
M IAA
C o n g u g a t i o n , d e c a r b o x y l a t i o n , a n d b i o s y n t h e s i s o f IAA o c c u r v i a
numerous p ath w a y s and a r e und er p r e c i s e m e t a b o l i c c o n t r o l
An a l t e r a t i o n
the
tissue
in
m etabolism
and t h e
or binding p ro te in s
as
w ell
as
A m utatio n
grow th o f
would
that
(see Rubery
likely
tissue.
1981)
a u x i n u p t a k e and t r a n s p o r t
in
IAA m e t a b o l i s m
or
affect
could
(Cohen 1983).
levels of
free
IAA i n
Changes i n a u x i n r e c e p t o r s
affect
w ithin
reception
sen sitiv ity
the tis s u e
could
to
(Jacobs
account
IAA,
1983).
for
the
39
m u tan t's
of
altered
grav itro p ic
sen sitiv ity
to
IAA,
greater
root elongation,
and
lack
in v o lv in g
IAA
response.
E n d o g e n o u s Au xi n C o n t e n t
To
in v estig ate
m etabolism ,
the
p o ssib ility
of
a
m utatio n
f r e e IAA c o n t e n t o f a g r a v i t r o p i c a n d g r a v i t r o p i c
determ ined.
High p r e s s u r e
liq u id
roots
wa s
c h r o m a t o g r a p h y was u s e d t o r e s o l v e
t h e IAA c o m p o n e n t o f t h e s a m p l e a n d p e a k h e i g h t w a s u s e d t o q u a n t i f y
t h e IAA ( F i g u r e 1 0 ) .
Figure
10 .
R e p r e s e n t a t i v e HPLC c h r o m a t o g r a m o f a b a r l e y r o o t IAA
e x t r a c t i o n sam ple.
T h e IAA i s d e t e c t e d b y f l u o r e s c e n c e
w i t h a p e a k r e t e n t i o n t i m e o f 12. 85 m i n u t e s .
TIM E (m in u te s )
An i n i t a l
experim ent
indicated higher
l e v e l s o f e n d o g e n o u s IAA i n
ro o ts of ag ra v itro p e s than g ra v itro p e s.
To t e s t w h e t h e r t h i s v a r i a t i o n
wa s a s s o c i a t e d
agravitropic
w ith
agravitropism ,
two
ind iv id u als
were
40
hybridized
w ith
endogenous
content
B etzes,
IAA l e v e l s .
betw een
p arents,
and
the
ag rav itro p e
sig n ifican t
( T a b l e 11).
roots
A lthough
gravitro p ic
1 07
d ifferen ces
and
w ere
Random a g r a v i t r o p i c
from
progeny were
sig n ifican t
d ifferen ces
parent,
B etzes,
ag rav itro p e
90,
found
in t h e i r
evaluated
and
w ere
findings.
root tissu e
observed,
no
segregating offsp rin g
and g r a v i t r o p i c p l a n t s a m p l e s fro m t h e
sam ples
are
sim ilar
to
Levels of
o th e r published
The IAA c o n t e n t o f m a i z e v e g e t a t i v e t i s s u e d e t e r m i n e d by g a s
chrom atography-m ass
Schulze
IAA
agrav itro p ic
1983 p o p u l a t i o n a l s o s h o w e d s i m i l a r e n d o g e n o u s IAA c o n t e n t s .
IAA f o u n d i n t h e s e
for
for
1977)
sp ectro sco p y
is
2 4 n g p e r g FW ( B a n d u r s k i
and
and m aize r o o t t i s s u e
is
45 n g p e r g FW ( P i l e t a n d S a u g y
1985),
T a b l e 1 1.
F r e e IAA c o n t e n t p e r g r a m FW o f p r i m a r y r o o t s f o r p a r e n t s .
a n d F 2 p r o g e n y o f B e t z e s X a g r a v i t r o p e 107 a n d B e t z e s X
a g r a v i t r o p e 90 c r o s s e s , a n d r a n d o m 1983 a g r a v i t r o p i c a n d
grav itro p ic p la n ts .
No. o f
sam ples
n g IAA
p e r g FW
6
2
5 9 . 9 H1 7 . 3
28.4 + 0.7*
5
5
3 5 .9 + 3 .2
39.4 + 9.2
13
12
52.4 + 4.8
54.6 + 5.6
24
19
50.8 + 3.6
47.9 + 4.7
■Parents
A g r a v i tr o p e (107,90)
G r a v itr o p e (Betzes)
F2
Progeny
A gravitropes
G ravitropes
1983 P l a n t s
A gravitropes
G ravitropes
T otals
A gravitropes
G ravitropes
* S ig nificant a t a p ro b ab ility
'
le v e l of 0.06.
41
The a g r a v i t r o p e ' s
greater
root
elongation,
tolerance
t o exogenous
IAA, a n d l a c k o f g r a v i r e s p o n s e m i g h t i n d i c a t e a c h a n g e i n IAA s y n t h e s i s
or m etabolism
l e a d i n g t o a d e f i c i e n c y o f f r e e IAA i n t h e r o o t t i s s u e . -
A pparently t h i s
i s n o t t h e c a s e . ' P i l e t and Saugy (1985) s t u d i e d
the
r e l a t i o n s h i p b e tw e e n a u x i n s and g r o w th w i t h g ro u p s o f f a s t and s lo w
grow ing corn ro o ts .
to leran t
of
The g r o u p w i t h g r e a t e r r o o t e l o n g a t i o n was n o t
exogenous
IAA a n d h a d
a
C o n v e rse ly , th e group o f slow g row ers
low er
relatio n sh ip
showed
d e c r e a s e from an o p t i m a l
as
A model p ro p o se d t o d e s c r i b e
endogenous
auxins
increase
or
l e v e l , g r o w t h r a t e d e c r e a s e s . The a g r a v i t r o p i c
m utant does not f i t t h i s
e x o g e n o u s IAA,
th at
I AA c o n t e n t .
e x p r e s s e d t o l e r a n c e o f exogenous
IAA a n d a h i g h e r e n d o g e n o u s IAA c o n t e n t .
th is
endogenous
model w ith i t s
f a s t e r grow th,
to leran ce of
a n d n o r m a l e n d o g e n o u s IAA l e v e l .
An a l t e r a t i o n i n a u x i n t r a n s p o r t o r r e c e p t i o n c o u l d a c c o u n t f o r
th e
a g r a v itro p e 's
tolerance,
unique
and l a c k o f f i t
to
grow th
ch a rac te ristic s,
the P i l e t
a n d S a ug y
sp ecific
(1985)
IAA
g r o w t h model.
A n o r m a l e n d o g e n o u s IAA l e v e l a n d i n c r e a s e d g r o w t h r a t e c o u l d i n d i c a t e
a lack of
sen sitiv ity
exogenous
IAA
was
s y n th e tic auxins.
reception
observed
and
it
Binding p r o t e i n s
was
A lack
grow th
receive,
sen sitiv ity
for
IAA a n d
to
not
r e s p o n s i b l e f o r . a u x i n t r a n s p o r t and
and r e s p o n s i v e t o p a r t i c u l a r au x in
and p o s s i b l y
o r respond to
of
sp ecific
Thus, the m u tatio n of a g ra v itro p ism
reg u lated
tran sp o rt,
e n d o g e n o u s IAA.
may b e h i g h l y s p e c i a l i z e d
com pounds.
auxin
to
IAA.
the
appears to
a b ility
of
the
involve
tissu e
to
42
SUMMARY AND CONCLUSIONS
The
b arley
m u tag en esis.
three
the
ag rav itro p ic
root
m utant
arose
through
chem ical
C r o s s e s b e tw e e n g r a v i t r o p e s and a g r a v i t r o p e s y i e l d e d
grav itro p es
m u tatio n
is
to
one a g r a v i t r o p e
controlled
by
in
a
F2 g e n e r a t i o n ,
sin g le
co m p le te ly dom inant over a g ra v itro p is m .
agravitropism
the
and t h e V lo c u s on t h e
gene
suggesting
w ith
g rav itro p ism
was
found betw een
No l i n k a g e
l o n g arm o f chrom osom e t w o o r t h e
H o r - 1 and H o r-2 l o c i on t h e s h o r t arm o f chrom osom e f i v e .
Due t o t h e
l i m i t e d n u m b e r o f t r a n s l o c a t i o n b r e a k p o i n t s and s m a l l F 2 p o p u l a t i o n
sizes,
no s i g n i f i c a n t l i n k a g e was fo u n d in t h e t r a n s l o c a t i o n s e r i e s
crosses.
The l o n g a r m s o f c h r o m o s o m e s o n e a n d f o u r r e m a i n u n t e s t e d f o r
lin k ag e to ag ra v itro p ism .
The lo n g arm o f c h ro m o s o m e f i v e and b o t h
arms o f chromosome s i x were w eakly t e s t e d .
F urther e x p lo ra tio n of the
b a r l e y chrom osom es by h y b r i d i z a t i o n
sp ecific
w ith
m arker genes
is
needed t o d e te r m in e th e chromosomal lo c a t i o n o f a g r a v itr o p is m .
Th e s e l f e d a g r a v i t r o p i c p o p u l a t i o n c o n t a i n e d g r a v i t r o p i c p l a n t s o f
qu estio n ab le
origin,
be
although
observed
to
m orphologically
an aly sis
could not d is tin g u is h
g rav itro p es
sim ilar.
and
agravitropes
H ordein
banding
w ere
p attern
b e t w e e n g r a v i t r o p e s and a g r a v i t r o p e s .
T h e r e was no e v i d e n c e t h a t t h e g r a v i t r o p e s d i f f e r e d f r o m t h e r e s t o f
the p o pulation,
the physiology
The
response.
and th e y w ere u t i l i z e d
in com parison t o a g r a v itr o p e s in
studies.
m u ta n t's
ro o ts
disp lay
a com plete
No m e a s u r a b l e c u r v a t u r e
absence o f
g rav itro p ic
w as f o u n d f o l l o w i n g up t o e i g h t
43
hours o f s tim u la tio n
in
lig h t or dark.
The s h o o t s a r e g r a v i t r o p i c .
T o t a l r o o t g r o w th was found t o be t h e sam e f o r m u ta n t and w i l d ty p e
seed lin g s.
seed lin g
H owever,
th e
ag rav itro p ic
and g r e a t e r e l o n g t i o n
difference
in grow th r a t e
could
per
m u ta n t had
root
indicate
than
colum ella c e lls .
for
w ild
ro o ts
type.
per
T his
a lack of grow th i n h i b i t o r or
d e c r e a s e d s e n s i t i v i t y t o su ch an i n h i b i t o r
Th e s t i m u l u s
the
few er
ro o t graviresponse
in th e m u tan t's
is
perceived
in
roots.
the
r o o t cap
A m y lo p lasts in th o s e c e l l s s e d im e n t w ith g r a v ity ,
g e n e ra tin g a s ig n a l f o r grow th response.
Root t i p
iheasured f o r g r a v i t r o p e s and a g r a v i t r o p e s
s t a r c h c o n t e n t s were
and fo u n d t o be t h e sam e.
M i c r o s c o p i c a n a l y s e s show ed n o r m a l a m y l o p l a s t movement i n t h e m u t a n t ' s
colum ella c e lls
not
involve
(Moore
1985 ).
These r e s u l t s
the p la n t's perception
indicate, the
m u t a t i o n may
of gravity.
G r a v i t r o p i c r e s p o n s e i s c o n t r o l l e d by g ro w th r e g u l a t o r s
roots.
A uxins r e d i s t r i b u t e l a t e r a l l y dow nw ard in s t i m u l a t e d r o o ts ,
c o lle c tin g in supraoptim al c o n c e n tr a tio n s
1 96 7 ).
w ild
Th e m u t a n t ' s
type
roots.
applications
(A n d r e a e
in th e
ro o t grow th i s
grow th
(K onings
i n h i b i t e d by a p p l i e d
IAA t h a n
M u ta n t and w i l d t y p e
of the
1967;
less
to
synthetic
Ingensiep
auxins,
in h ib it
roots
respond
NAA a n d . 2 , 4 - D .
1982) h a v e s h o w n t h a t t h e
of a p a r t i c u l a r auxin s tro n g ly a f f e c ts
sim ilarly
to
Previous stu d ie s
tis su e 's
m etabolism
t h e amount o f g ro w th i n h i b i t i o n .
A c h a n g e i n IAA m e t a b o l i s m m i g h t b e e x p r e s s e d .as a c h a n g e i n f r e e
I AA
co n cen tratio n
in
th e
a g r a v i t r o p i c and g r a v i t r o p i c
m utation
may i n v o l v e
m etabolism
and
ro o ts.
ro o ts
sen sitiv ity
free
I AA
Endogenous
I AA c o n t e n t s
are not d iffe re n t,
to
lev els.
IAA r a t h e r
A
than
change
in
suggesting
an a l t e r a t i o n
th e
of
the
in
recep to r
44
binding
p ro tein s
resp o n sib le
for
the
tran sp o rt
and
re co g n itio n
of
a u x i n s c o u l d c a u s e t h e t i s s u e t o b e l e s s s e n s i t i v e t o e n d o g e n o u s IAA.
T his
lack of s e n s i t i v it y
could
re su lt
i n an i n c r e a s e d g r o w t h r a t e ,
t o l e r a n c e t o e x o g e n o u s a p p l i c a t i o n s o f IAA,
and a g r a v i t r o p i s m .
45
LITERATURE CITED
A n d r e a e , W. A.
1967.
U ptake and m e ta b o lis m o f i n d o l e a c e t i c a c id ,
n a p t h a l e n e a c e t i c a c id , and 2 ,4 - d i c h l o r o p h e n o x y a c e t i c a c i d by p e a
r o o t s e g m e n ts in r e l a t i o n t o g r o w th i n h i b i t i o n d u r i n g and a f t e r
auxin a p p lic a tio n .
Can. J . B o t . 4 5 : 7 3 7 - 7 5 3 .
A r s I a n - C e r i m , N. 1 9 6 6 . T h e r e d i s t r i b u t i o n o f r a d i o a c t i v i t y i n
g e o t r o p i c a l Iy s t i m u l a t e d h y p o c o t y I s o f H e l i an t h u s a n n u u s
p r e t r e a t e d w i t h r a d i o a c t i v e c a l c i u m . J . Exp. B o t . 1 7 : 2 3 6 - 2 4 0 .
A u d u s , L. J . 1 9 7 5 . G e o t r o p i s m i n r o o t s , p . 3 2 7 - 3 6 4 . I n J . G. T o r r e y a n d
D. T. C l a r k s o n ( e d . ) T h e d e v e l o p m e n t a n d f u n c t i o n o f r o o t s .
A c a d e m i c P r e s s , New Yo rk .
A u d u s , L. J . 1 9 7 9 . P l a n t g e o s e n s o r s . J . E x p . B o t . 3 0 : 1 0 5 1 - 1 0 7 3 .
A u d u s , L. J . , a n d M. E. B r o w n b r i d g e . . 1 9 5 7 . S t u d i e s o n t h e g e o t r o p i s m o f
r o o t s . I. Growth r a t e d i s t r i b u t i o n d u r i n g re s p o n se and t h e e f f e c t s
o f a p p l i e d a u x i n s . J . Exp. B o t . 8 : 1 0 5 - 1 2 4 .
B a r l o w , P. W. 1 9 7 4 . R e c o v e r y o f g e o t r o p i s m
c a p . J . Exp. B o t . 2 5 : I 1 3 7 - 1 146.
a f te r rem oval of th e ro o t
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