RNAi Based Strategies to Control Meloydogine spp. Infection in Soybean

The plant-parasitic nematode Meloidogyne incognita is considered the most important plant pathogen due to its worldwide distribution and severe damage caused to a large variety of agronomical important crops. Three groups of genes were selected for silencing: genes expressed in dorsal glands, responsible for feeding site formation; genes involved with digestion; and genes homologues to lethal genes. First we determined the relative expression in different nematode developmental stages by qPCR and then were subcloned and introduced the different RNAi vectors into tobacco or in soybean plants. The effects of silenced target genes were evaluated by qPCR and nematode reproduction. Data from tobacco plants at 45 DAI showed reduction in egg number/root gram of 28-37% with HSP90 gene, 67-76% with Isocitrate Lyase, and 30-40% with three proteinase genes. For soybean plants, we characterized the expression of the ubiquitin conjugation factor in roots at 7, 14, 21 and 28 DAI with M. incognita. Data showed 6-7 fold transcripts abundance in inoculated roots compared to non-inoculated soybean roots, indicating that the UceS8.3 is a useful biotechnological promoter. Gene fragments related to RNA splicing from M. incognita and H. glycines were subcloned downstream the UceS8.3 promoter in RNAi vector and inserted in soybean. T3 GM plants were highly resistant to nematodes, with 71-91% reduction in egg number/root gram at 35 DAI. In conclusion, some target genes showed deleterious phenotype and are promising genes to be used in GM crops by RNAi to the nematode control.

Supported by EMBRAPA, UCB, CNPq, CAPES