Several nematodes parasitize a wide variety of plants and animals including human beings. A nematode Meloidogyne incognita infects the roots of tobacco plants and causes a great reduction in yield. A novel strategy was adopted to prevent this infestation which was based on the process of RNA interference (RNAi). RNAi takes place in all eukaryotic organisms as a method of cellular defense. This method involves the silencing of a specific mRNA due to a complementary dsRNA molecule that binds to and prevents translation of the mRNA (silencing). The source of this complementary RNA could be from infection by viruses having RNA genomes or mobile genetic elements (transposons) that replicate via an RNA intermediate. Using Agrobacterium vectors, nematode-specific genes were introduced into the host plant. The introduction of DNA was such that it produced both sense and anti-sense RNA in the host cells. These two RNA’s being complementary to each other formed a double-stranded (dsRNA) that initiated RNAi and thus, silenced the specific mRNA of the nematode.

Strategy to prevent infestation of Meloidogyne incognita in tobacco plants

Meloidogyne incognita is a nematode that infects the roots of tobacco plants, leading to a significant reduction in yield. To tackle this infestation, a novel strategy was adopted, which involved the following processes:

1. RNAi (RNA interference):
RNAi is a biological process in which small RNA molecules inhibit the expression of specific genes by binding to their messenger RNA (mRNA) transcripts. In the case of Meloidogyne incognita infestation, RNAi was used as a strategy to prevent the nematode's genes from being expressed, thereby reducing its ability to infect tobacco plants. This process involves the following steps:
- Introduction of double-stranded RNA (dsRNA) specific to the nematode's target genes into the plant cells.
- The dsRNA is then processed into small interfering RNAs (siRNAs) by an enzyme called Dicer.
- These siRNAs guide a protein complex called RNA-induced silencing complex (RISC) to target and degrade the complementary mRNA molecules of the nematode genes.
- By silencing the nematode's genes, the infestation can be prevented or reduced, resulting in improved yield.

2. mRNA silencing:
mRNA silencing is a mechanism by which mRNA molecules are degraded or prevented from being translated into proteins. This process can also be utilized to prevent the expression of specific genes in the nematode. By targeting and degrading the mRNA molecules of essential genes in Meloidogyne incognita, the nematode's ability to infect tobacco plants can be hindered.

3. Anti-sense RNA technology:
Anti-sense RNA technology involves the introduction of antisense RNA molecules into cells, which are complementary to specific mRNA targets. These antisense RNA molecules bind to the target mRNA molecules and prevent their translation into proteins. By designing antisense RNA molecules specific to genes essential for the nematode's survival or virulence, their expression can be blocked, thereby impeding the infestation of Meloidogyne incognita in tobacco plants.

Conclusion:
The strategy adopted to prevent the infestation of Meloidogyne incognita in tobacco plants involved the processes of RNAi, mRNA silencing, and anti-sense RNA technology. By targeting and inhibiting the expression of essential genes in the nematode, the ability to infect tobacco plants is significantly reduced, leading to improved plant yield.