TMV (tobacco mosaic virus) is a plant virus that infects tobacco and other solanaceous plants like tomatoes and potatoes. It causes characteristic mosaic and mottling patterns on the leaves of infected plants. TMV is composed of a single-stranded RNA genome enclosed in a protein capsid. The virus enters the host plant through wounds in the leaves or stems and uses the plant's cellular machinery to replicate its RNA and proteins, which then self-assemble to form new virus particles that spread the infection. Control methods include crop rotation, rogueing infected plants, and developing resistant varieties.
2. INTRODUCTION
• TMV (tobacco mosaic virus) is the most serious pathogen causing mosaic on tobacco
leaves .
• Tobacco mosaic virus (TMV) is a plant virus that belongs to the genus Tobamovirus.
• named so because it majorly infects tobacco plants, potatoes, tomatoes and other
members of the Solanaceae family.
• The infection creates a mosaic like pattern, mottling and discoloration of the leaves
• TMV is the most resistant virus known so far of which the thermal death point is 90°C for
10minutes .
• This is the first virus that was crystallized in 1935 by WM Stanley in the USA
3. SYMPTOMS
• After infection it develops systems of lighteing of leaf colour among the virus in early stages.
• turns into light and dark mosaic symptoms.
• Among the veins green colour turn into dark green and terminal region turn into chloronic.
• Sometime dark green blisters appear in leaf blade.
• If the plants are infected early in season they become stunted .
• The virus reduces the yield as the quality of products i.e. The nicotine content is decreased
by 20% to 30% .
8. • has a rod-like appear appearance that is 300 nm long with a diameter of 18
nm.
• covered by a protein shell called capsid that encloses the virus’s genetic
material.
• The genetic material is a single-stranded RNA molecule.
• The capsid is made up of 2130 molecules of coat proteins that assemble in a
rod-like helical.
• RNA is found in a coiled manner inside the capsid coat and is made up of
approximately 6395 nucleotides
• It has structural chirality and inherent symmetry in the structure which gives
the organism an easy way for chemical or genetic modifications
11. PROTEIN SYNTHESIS
• Takeba (1975) demonstrated the direct entry of TMV into the isolated protoplast
from mesophyll cells of tobacco
• After making entry, RNA rapidly starts uncoating by removing the subunits from
the capsid by using host enzyme.
• The parental RNA is localised in nucleus but not in cytoplasm . It performs two
important functions :
✓ It acts as mRNA and directs the synthesis of protein
✓ function and template for synthesis of complimentary strand.
12. • The virus RNA utilizes the amino acids ribosomes and tRNA of the
host and synthesizes the complementary strand and proteins
I.e. Coat protein of 17500 Dalton’s and other polypeptides (mol.
Weight 1,60,000)
• The ratio of nucleic acid and proteins differ with each virus.
• Each protein subunits of TMV consist of 158 amino acid making a
total number to about 17531.
13. TRANSMISSION
• TMV is transmitted through the cell sap of host and enters a new host
through wound incision.
• wound is caused in plants due to various cultural operations such as
clipping and topping the shoot.
• not seed transmitted but act as seed contaminant.
• also transmitted by wind and water.
• Insects are also most important in its spread
14. CONTROL
• by crop rotation
• regular roguing diseased plants and weeds,
• Effective Sanitation
• use of resistant varieties.
15. APPLICATIONS
• Tobacco mosaic viruses are being widely used as viral vectors to
deliver the gene of interest into plant cells and to produce plants
with better quality and quantity.
• It also finds some use in biomaterial and nanotechnology devices
• used to demonstrate for development of coat protein-mediated
resistance, replicase mediated resistance, and movement protein-
mediated resistance.
