Feeding RNAi in the Twospotted Spider Mite, Tetranychus urticae

RNA interference (RNAi) technology is being developed to control insect pests. In this study, we conducted research to determine if RNAi could be used to control twospotted spider mites, Tetranychus Urticae. The twospotted spider mites are well known as a worldwide polyphagous pest due to their unique physiological and behavioral characteristics, the extraordinary ability to detoxify wide range of pesticides, and their adaptation ability to the wide-range of host plants. Leaf-disc double-stranded RNA (dsRNA) feeding assays were employed to test nine candidate genes involved in action of juvenile hormone (JH) and ecdysteroids. The result showed that four genes caused significant lethality. For applications in the field, transgenic tobacco and Arabidopsis plants expressing dsRNA targeting Methoprene-tolerant gene (Met, a JH receptor) were generated and tested whether spider mites can survive on these plants. We did not observe significant mortality in spider mites feeding on Arabidopsis transgenic plants, but those mites raised on tobacco transgenic plants showed 48% mortality: the mortality was observed during molting and nympal stages. These data suggest that understanding the mode of action of hormones in mites could help in finding lethal genes for producing transgenic plants that could be used for development of RNAi-based control of twospotted spider mites.