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Tobacco mosaic virus (TMV) is a rod-shaped virus belonging to the Tobamovirus genus. It infects plants like potatoes, tomatoes, and members of the Solanaceae family. This was the first virus to be discovered whose primary host is tobacco plants.
- Tobacco mosaic virus comprises a capsid, a surrounding protein coat, and a single-stranded RNA (Ribonucleic acid).
- After entering the plant cell, the protein coat separates, and the nucleic acid part instructs the plant cell to generate more virus protein and nucleic acid.
- This disrupts the normal functioning of the cell.
- Due to the infection, leaves might suffer patterns, mottling and discolouration.
- Symptoms of tobacco mosaic virus differ depending on the type of plant affected, maturity of the plant, virus strain involved, and environmental factors.
In this article, we have provided a complete overview of TMV along with its structure and life cycle.
| Table of Content |
Key Terms: Tobacco Mosaic Virus, TMV, Tobacco Plants, Tobacco mosaic virus Disease, Virus, Tobamovirus Genus, Structure of Tobacco Mosaic Virus, RNA
Discovery of Tobacco Mosaic Virus
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Around 1857, Tobacco farmers in the Netherlands started reporting a new tobacco disease.
- In 1882, German scientist Adolf Mayer, after conducting research, published the first article on tobacco mosaic virus disease, a serious disease of tobacco plants.
- Using capillary glass tubes filled with sap from infected plants, he demonstrated how the disease could be spread to healthy tobacco plants and proved it a contagious disease.
- Later, between 1887 and 1890, Dmitri Ivanowsky, a Russian microbiologist, initiated studies on tobacco mosaic disease.
- In addition, he carried out an experiment to identify the disease's causative organism.
- Consequently, he deduced that a nonbacterial agent causes the Tobacco mosaic virus in plants.
- After examining the characteristics of the causal agent, Martinus Beijernick, another scientist, provided his explanation.
- Not only did he coin the name "virus", but he also claimed it to be the causal organism.
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Structure of Tobacco Mosaic Virus
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The virus has since been described in many different forms or strains.
- Tobacco mosaic virus is a plant virus primarily composed of single-stranded RNA and a protein shell called a capsid.
- The virus is in the shape of a 300-nm-long rod with an 18-nm-diameter diameter.
- The capsid is composed of 2130 molecules assembled in a rod-like helical structure consisting of 16.3 proteins per helix turn.
- Similarly, RNA, coiled inside the capsid coat, comprises 6395 nucleotides.
- It has been reported that TMV can persist and spread for up to 50 years when stored at 40°F.
- Leaves of an infected plant show symptoms such as cupping, curling, extension (strapping), roughening, wrinkling, and other growth abnormalities.
Life Cycle of Tobacco Mosaic Virus
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Aphids, flies, and other insects are examples of the vectors that allow TMV to penetrate plant host cells. After entering the cell, the virus multiplies and uses plasmodesmata to migrate to nearby cells.
- By coming into close contact with diseased plants, the virus might spread to other healthy plants.
- Within the host organism's cell, the virus releases its genetic material to translate several mRNAs to replicate and multiply.
- Both the viral genome and the capsid proteins are replicable by these mRNAs.
- After that, these proteins come together to make a Tobacco mosaic virus cell that is all set to attack a new cell.
Applications of Tobacco Mosaic Virus
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Tobacco mosaic virus has some important applications in the biotechnological field, including:
- TMVs are widely used as viral vectors to introduce desired genes into plant cells, improving the quality and quantity of plants produced.
- They also play a role in the production of nanomaterials and biomedicine.
- Tobacco Mosaic virus is a prime choice for incorporation into battery electrodes because of its cylindrical shape, high aspect ratio, self-assembling nature, and capacity to absorb metal coatings (nickel and cobalt) into its shell.
- The TMV vector also helps enable the C. acutatum to divide exogenous GFP into six subcultures.
Things to Remember
- The Tobacco Mosaic Virus is a very stable virus that can live for a long duration of time.
- It is made up of single-stranded RNA genomes.
- The virus is spread by plant-to-plant contact, whether it occurs naturally or through farmer hands, contaminated clothing, or infected instruments.
- Two viruses that trigger viral infection are bacteriophage and tobacco mosaic virus.
- It has a rod-shaped structure coated with a protein called capsid.
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Sample Questions
Ques. What are the symptoms of TMV infected plants? (3 marks)
Ans. Plants that have the infection are often stunted, discolored, and occasionally twisted. The virus commonly causes light and dark green mottling on tomato leaves.
- The leaf's darker green sections frequently appear thicker than its lighter sections.
- Usually, embryonic development is limited and the leaves curl downward in a twisted manner.
Ques. What are the plant diseases caused by viruses? (2 marks)
Ans. Virus-induced plant diseases include the following:
- Tomato spotted wilt virus,
- Tomato yellow leaf curl virus,
- Cucumber mosaic virus,
- Potato virus Y,
- Cauliflower mosaic virus
Ques. Which technique is most frequently used for gene transfer in plants? (2 marks)
Ans. Particle bombardment, protoplast electroporation, or Agrobacterium-mediated transformation are the methods used to genetically modify plant cells. Plants can only undergo agrobacterium-mediated transformation, which has been shown to be the most effective method for transforming plant genes.
Ques. How do plants respond to TMV? (2 marks)
Ans. Plants infected with the tobacco mosaic virus (TMV) may produce less chlorophyll. This changes the colour of the leaves. As a result, the concentration of leaves’ pigment decreases, which in turn makes it more difficult for the plant to perform photosynthesis.
Ques. Are yellow leaves caused by TMV? (1 mark)
Ans. Yes, infected plants may also exhibit less noticeable signs like stunted growth or yellowing of leaves that could be mistaken for a nutrient shortage.
Ques. What are the methods to cure TMV disease? (3 marks)
Ans. TMV has no known treatment or cure. There are a few strategies to avoid infections:
- Throw away contaminated plants and thoroughly decontaminate growth regions.
- Don't grow decorative plants and vegetables transplants in the same environment.
- Workers who use tobacco products should clean their hands immediately after work.
Ques. What is the largest virus that affects plants? (2 marks)
Ans. A genus of RNA viruses known as potyvirus causes the annual destruction of crop fields. The genome of the potyvirus is a spirally arranged single-stranded, linear, positive-sense RNA that is approximately 10 kb in size.
Ques. What is the difference between the life cycle of a plant virus and animal virus? (2 marks)
Ans. When a virus particle enters a host cell, its life cycle begins. In plants, this could occur through physical contact or an injury that could be transmitted by an insect vector.
On the other hand, in animals, viruses are spread through direct contact or by insects, and they enter the host cell through phagocytosis.
Ques. Why are viruses considered as an important organism in biotechnological research and studies? (2 marks)
Ans. The fact that viruses possess characteristics of both living and non-living creatures makes them useful in biotechnology research.
- They can be used to diagnose infections, administer vaccinations, and cure diseases.
- They are used as research instruments to create new drugs.
Ques. What are the ways to kill TMV in labs? (3 marks)
Ans. The two most common and efficient methods to kill TMV are:
- The least expensive and most efficient way to eradicate the virus from infected instruments is to apply a solution of 10% household bleach and leave it on the surface for one minute.
- TMV is a thermostable virus which means it can tolerate up to 50 °C (120 °F) for 30 minutes on a dried leaf.
- Therefore, beyond this temperature, TMV may die.
Ques. What is the lifespan of TMV? (2 marks)
Ans. The virus can be found in plant-based products, most notably tobacco products. It has been reported that TMV can persist and spread for up to 50 years when stored at 40°F. TMV is a very stable virus that can live for a longer duration of time.
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