Plant Tissue Culture
T.C.
 Refers to technique of
growing plant cells, tissues,
organs, seeds
or other plant parts in a
sterile environment on a
nutrient medium
History
In 1902 Haberlandt
proposed that single plant
cells could be cultured
Haberlandt
did not culture them
himself
1930’s
White worked on T.C.
discovery of plant growth
regulators
1930’s
importance of vitamins was
determined for shoot and root
culturing
1930’s
Indole-Acetic Acid
IAA
discovered in 1937
IAA
2,4-D
Dicamba
NAA
IBA
all synthetic hormones
1957-58
Miller and Skoog
University of Wisconsin Madison
discovered Kinetin
Kinetin
a cytokinin
plays active role in
organogenesis
1958
Steward developed somatic
embryo from carrot cells
1958-60
Morel cultured orchids and
dahlias
freed them from a viral
disease
1962
Murashige and Skoog
published recipe for MS
Medium
60’s & 70’s
Murashige cloned plants in
vitro
promoted development of
commercial plant T.C. labs
1966
raised haploid plants from
pollen grains
1972
used protoplast fusion to
hybridize 2 species of
tobacco into one plant
contained 4N
4N
all chromosomes of both
plants
70’s &80’s
develop techniques to
introduce foreign DNA into
plant cells
beginning of genetic
engineering
T.C. Media
functions
provide H2O
provide mineral nutritional
needs
T.C. Media
provide growth regulators
Provide vitamins
provide organic compounds
T.C. Media
provide access to
atmosphere for gas exchange
serve as a dumping ground
for plant metabolites
T.C. Media
H2O is usually distilled
minerals must provide 17
essential elements
energy source and carbon
skeletons - sucrose is
preferred
Vitamins
thiamine
pyridoxin
nicotinic acid
biotin
Vitamins
citric acid
ascorbic acid
inositol
Growth Regulators
auxins and cytokinins
gibberellic acid
abscissic acid
pH of media
usually 5.0-5.7
Media
must be sterile
autoclave at 250 F at 15 psi
for 15 minutes
T.C. Stages
Explanting- Stage I
get plant material in sterile
culture so it survives
provide with nutritional and
light needs for growth
Stage II
rapid multiplication
stabilized culture
goal for a commercial lab
difficult and time
consuming to maintain
Stage II
occurs in different
pathways in different plants
Rooting - Stage III
may occur in Stage II
usually induced by changes
in hormonal environment
lower cytokinin
concentration and increase
auxin
Rooting
may skip stage III and root
in a greenhouse
Stage IV
transplantation and
aftercare
usually done in greenhouse
keep RH high (relative
humidity)
Stage IV
gradually increase light
intensity and lower RH after
rooting occurs
allows plants to harden and
helps plants form cuticle
Cuticle
waxy substance promotes
development of stomates
plants in T.C. don’t have
cuticle
Explant
portion of plant removed
and used for T.C.
Important features
size
source - some tissues are
better than others
Explant
species dependent
physiological age - young
portions of plant are most
successful
Explant
degree of contamination
external infestation - soak
plant in sodium hypochlorite
solution
Explant
internal infection - isolate
cell that is not infected
roots - especially difficult
because of soil contact
Explant
herbaceous plants
soft stem
easier to culture than
woody plants
Patterns of
multiplication
stage II - light 100-300 foot
candles
callus - shoots - roots
stage III - rooting - light
intensity 1000-3000 foot
candles
Genetic
transformation
permanent incorporation of
new or foreigh DNA into
genome of cell
Transformation
methods
protoplast fusion
cell wall is enzymatically
removed from cell
Protoplasts
naked plant cells
from 2 different plants can
be mixed together and forced
to fuse
Protoplast fusion
results in heterokaryon
cell containing two or more
nuclei from different cells
homokaryon - from same
cell
Protoplast fusion
allowed to regenerate cell
wall and then grow into
callus
callus turns to shoots
Shotgun approach
DNA coated micro bullets
of gold or tungston
shot into growing cells
DuPont holds the patent
Shotgun approach
injures cells
random success rate
PEG
Polyethylene glycol
pores open similar to
electroporation
Ti Plasmids
Tumor inducing
Agrobacterium
temefasciens
infect cells with
agrobacterium which
contains desired DNA
Ti Plasmids
monocots resist
agrobacterium infection
researchers are working to
overcome this
Luciferase
an enzyme
put into tobacco using Ti
plasmid
Luciferase
when transformed tobacco
plants are watered with
solution containing Luciferin
they break it down and emit
light
Luciferase
glowing in the dark
like a fire fly
Screening techniques
used to identify if culture
has taken on desired new
trait
Examples
sensitivity to antibiotics
color
sensitivity to excess
deficiencies of substances in
growth media
Conventional
plant breeding
egg cell gives half the
chromosomes and almost all
of the cytoplasm
male only gives its
chromosomes
Cont…….
This condition is called
maternal cytoplasmic
inheritance
Microinjection
single cells from culture are
held stationary with gentle
suction
injected with a tiny syringe
loaded with DNA
Microinjection
done under electron
microscope
Electroporation
desired DNA in solution
outside cell
high energy pulses - 50,000
volts
for a millisecond
Electroporation
cause tiny pores to open
allows DNA to enter the
cell