RNAi of egg developmental gene Mi-vit2 of the root-knot nematode, Meloidogyne incognita

The root-knot nematode (RKN), Meloidogyne incognita is a very serious crop pest causing substantial yield losses. RNA interference (RNAi), a tool for studying reverse genetics, is being exploited for developing novel management strategies for plant parasitic nematodes (PPNs). The host-delivered RNAi (HDRNAi) against specific nematode genes of importance has shown promising results in managing PPNs. This study targeted the silencing of the gene vit-2, belonging to the vitellogenin gene family and responsible for producing copious yolk required in the eggs for post-embryonic larval development and fertility. Transgenic Arabidopsis plants expressing dsRNA targeting vit-2 showed 59.17% reduction in root galls, 41.75% reduction in the number of adult nematode females, 49% reduction in the number of egg masses, and 32.84% reduction in the number of eggs per egg mass compared to wild types. Hatching tests of eggs obtained from the transgenic lines revealed poor hatching i.e., 57.5% in comparison to 86.5% in the control lines. Morphometrics of the progenies obtained from the transgenic Arabidopsis lines showed 19.79% and 16.75% reduction in width and length respectively of eggs collected from the transgenic line as compared to the control line. On the other hand, no significant change in the morphometrics of the juveniles was observed. However, the qRT-PCR result showed 5-fold upregulation in the target gene vit-2 from the females obtained from the transgenic line which is contradictory to the phenotypic observations. The reason for such a result could be because the gene, vit-2 belongs to a multigene family. Another reason could be that the expression of the gene may be life cycle stage linked, as the gene expresses in the intestine of the nematode. Comparative gene expression studies at different life stages may shed more insights on it. Also, extensive study on the complete set of genes from the vitellogenin gene family is needed.