RNA Interference Silencing in Root-knot Nematodes

The root-knot nematodes (RKN) belonging to the genus Meloidogyne are obligate and sedentary endoparasites that infect wide range of plant species. By parasitizing the root system, they disrupt the water and nutrient uptake thus affecting the whole plant causing significant reduction in the crop yield. They pose huge losses of several million dollars worldwide. Use of chemical nematicide, including soil fumigants such as methyl bromide was the most reliable strategy of controlling the rootknot nematodes. Recently, molecular strategies such as RNA interference (RNAi) mediated nematode gene silencing, R gene transformation, expression of proteins detrimental to RKN are gaining importance. RNAi is used for downregulating the expression of specific gene in several organisms, particularly free-living nematode Caenorhabditis elegans. RNAi strategy has been widely used for silencing the target genes in plant parasitic nematodes. Nearly 79,978 ESTs analysed from various developmental stages of Meloidogyne species has gained entry into the GenBank. The complete genome sequencing of M. incognita and M. hapla provides information regarding the parasitism genes and their success in parasitizing the plants. Recent RNAi approach has resulted in successful reports suggesting suppression of genes essential for nematode development, survival and parasitism in plants. These studies may further serve as a foundation for identification of novel genes and their role in parasitism and could be used as target genes for silencing thus conferring resistance to plants. This review focuses on the progress made towards the development of transgenic plants resistant to RKN through RNAi approach.