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Structure of TMV

Tobacco Mosaic Virus (TMV) is a rod-shaped virus approximately 300 nm long and 18 nm wide. It consists of a single-stranded RNA (ssRNA) genome surrounded by a protein coat (capsid) made of 2,130 identical protein subunits arranged helically. The RNA, about 6,400 nucleotides long, is coiled within the capsid and interacts with the protein subunits. TMV lacks a lipid envelope, making it highly stable and resistant to environmental stress like heat and desiccation.

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General Characteristics

1. Host Range:
   TMV infects over 150 plant species, primarily in the Solanaceae family, such as tobacco, tomatoes, and peppers.
2. Symptoms:
   Infected plants show mosaic patterns of light and dark green patches, distorted leaves, stunted growth, and reduced yields.
3. Transmission:
   TMV spreads mechanically through contact with infected plants, contaminated tools, or wounds in plant tissues. It is not transmitted by insects.
4. Replication:
   TMV replicates in the cytoplasm of host cells, using its RNA genome to produce viral proteins and new RNA strands.
5. Stability:
   TMV is highly stable, surviving in dried plant material for years and resisting heat and chemicals.
6. Economic Impact:
   It causes significant crop losses, requiring strict hygiene and the use of resistant plant varieties for management.
7. Historical Importance:
   Discovered in 1892 by Dmitri Ivanovsky, TMV was the first virus identified. Wendell Stanley later crystallized it in 1935, marking the beginning of modern virology.

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Scientific Significance

TMV has been a model for studying virus structure, replication, and host interactions. Its discovery and research have provided critical insights into molecular biology and virology.