Tobacco mosaic virus
M.M. Hernandez
Tobacco mosaic virus
TMV
• Genus Tobamovirus
15 members
naked, rigid rod,
+ unsegmented ss RNA
• No family assignation by ICTV
STRUCTURAL FEATURES OF TMV
CAPSID
30 nm
Helical symmetry
RNA genome
18 nm
2 nm
NC protein
Images:P. Sforza, 2001
www.ppws.vt.edu/~sforza/tmv/tmv.html
TMV genome organization
6,395 nt
Capsid CP
Replicase RdRp
5’ cap
183K
126 K
17.6 K
30 K
UAG (leaky)
Movement MP
MT-Hel
tRNAhis
Host: Nicotiana tabaccum
(Solanaceous ) & other 9 plant families
susceptible too
Disease:Mosaic (calico)
Mosaic disease on Tobacco leaf
Chlorosis
Stunting
Necrosis
Mosaic disease: significant losses in yield & $ value
TMV Life cycle
5’ cap
Host Rb
a) Virus entry trough
abrasions on plant
tissue. Inside cell
associates with ER
b) spontaneous release
of few capsid (CP)
subunits 5' end of
genome is uncovered
c) Host ribosome
attaches to viral RNA,
moves down displacing
more CP units …/…
Modification of a diagram from: L. Stannard, Department of Medical Microbiology, U. of Cape Town
TMV Life cycle
5’
(cont.)
d) Ribosome meets start
codon, translates first two
proteins (126K ,183 K) while
uncoating continues
“co-traslational disassembly”
e) 126 K ( MET-Hel) & 183 K
( RdRp) use viral RNA as
template to make full length
complementary neg. strand
RNA
…/…
Modification of a diagram from: L. Stannard, Department of Medical Microbiology, U. of Cape Town
TMV Life cycle
RdRp
+ Strand (genome)
(cont.)
Neg. strand
f) Neg. RNA strand used
by viral replicase
(RdPp/MET-Hel ) as
template for +RNA
promoters
g) Also, neg. RNA strand
has internal promoters
used by replicase to
make mRNA for 30K
protein (MP) and 17.5 K
(CP)
Transcription by RdRp
MP mRNA
CP mRNA
TMV Life cycle
(cont.)
h) MP combines
with viral +RNA
to move it into
new plant cells
through
plasmodesmata
http:www.sunysb.edu/biochem/BIOCHEM/facultypages/citovsky/TMV-TransportModel-III2.jpg
TMV Life cycle
(cont.)
i) Accumulation of +RNA
& CP proteins stimulates
assembly of progeny
virions
Viral RNA interacts with
discs
CP units self assemble
into discs
Electrostatic interaction stabilizes structure
into helix
M. Olvera de la Cruz
TMV Life cycle
(cont.)
j) massive TMR replication
occur in the X-bodies
(viroplasmas)
Szecsi et al. 1999
Hamacher et al. 2003
TMV Life cycle
(cont.)
k) Virus will remain in plant tissue and sap until delivered to
a new plant host usually by mechanical means
TMV diagnosis
• Symptoms
• E.M. & Serology
• RT-PCR & RFLP
Letschert et al. 2002
HTTP;//BAKERLAB.BERKELEY.EDU/?IMG=1
Current Research on TMV
• Improving diagnostic
techniques
• Characterization of
MP and viral
movement through
plant
• Characterization of
the Helicase & RdRp
Questions?
REFERENCES
Agrios G. N. 1988. Plant Pathology Third Edition. Academic Press, Inc. San Diego
pp: 658663
Ashby J., E. Boutant, M. Seemanpillai, A. Sambade, C. Ritzenthaler, M. Heinlein. 2006. Tobacco
Mosaic Virus Movement Protein Functions as a structural Microtubule-Associated Protein. Journal of
Virology. 80(17):8329-8344
Bos L. 1999. Plant Viruses Unique and intriguing pathogens. Backhuys Publishers Leiden
Dovas C., K. Efthimious, N. I. Katis. 2004. Generic detection and differentiation of tobamoviruses by a
spot nested RT-PCR-RFLP using dI-contining primers along with homologous dG-containing primers.
Journal of Virological Methods. 117:137-144
Goelet P., Lomonossoff G. P., Blutler P. JG, Akam M. E., Gait M. J., and Karn J., 1982. Nucleotide
sequence of the tobacco mosaic virus RNA. Proc. Natl. Acad. Sci. U.S.A. 79: 5818-5822
Goregaoker S. P. and J. N. Culver. 2003. Oligomerization and Activity of the Helicase Domain of the
Tobacco Mosaic Virus 126- and 183-Kilodalton Replicase Proteins. Journal of Virology. 77 (6): 35493556
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Hirashima K. and Y. Watanabe. 2003. RNA Helicase Doamin of Tobamovirus Replicase Executes
Cell-to-Cell Movement Possibly through Collaboration with its Nonconserved Region. Journal of
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Horst K.R.(reviser), 2001 Westcott=s Plant Disease Handbook Six Edition. Kluwer Academic
Plublishers.Boston pp:511-513
Jacobi V., G.D. Bachand, R.C. Hamelin and J.D. Castello. 1998. Development of a multiplex
immunocapture RT-PCR assay for detection and differentiation of tomato and tobacco mosaic
tobamoviruses. Journal of Virological Methods 74 (2):167-178
International Committee on Taxonomy of Viruses (ICTV) 2002. ICTVdB Virus Descriptions.
71.0.1.0.001 Tobacco mosaic virus (vulgare strain; ssp. NC82 strain). Retrieved November 22, 2002,
from: http://www.ncbi.nih.gov/ICTVdb/ICTVdB/71010001.htm
Kawakami F. M., R.W. Kim, R.N. Beachy. 2006 Domains of tobacco mosaic virus movement protein
essential for its membrane association. Journal of General Virology 87(9):2699-7707
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Imprint of the Haworth Press Inc. New York
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Bundesanstalt fur Land-und Forstwirtschaft 357
Letschert B., A Gunter, L. Dietrich-Eckhardt, P. Willingmann, C. Heinze., 2002. Detection and
differentiation of serologically cross-reacting tobamoviruses of economical importance by RT-PCR and
RT-PCR-RFLP. Journal of Virological Methods 106:1-10
Lucas G. B. , C.L. Campbell, and L.T. Lucas, 1985. Introduction to Plant Diseases Identification and
Management. The AVI Publishing Company, Inc. Westport Connecticut. pp 254-261
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MacMills Publishing Co., INC. London
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183-Kilodalton Replication Proteins Which bind Specifically to the Viral 3'-Terminal tRNA-like Structure.
Journal of Virology 77(16 ) 8669-8675
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Springer-Verlag, Berlin
1. Solution of TMV Capsid Proteins
Electrostatic repulsion inhibits
2. Add ssTMV+ RNA (assembly
infective virus): Electrostatic
attraction stabilizes viral assembly.
+ protein +protein aggregation.
Salt (M)
ZRNA= -1/mer
3. Sphere-like (icosahedral) RNA virus
(Tsuruta et al)
Acidity
4. Capsid + Hole (density ≈ RNA crystal)
self-assembles from capsid protein + viral
RNA solution