RNA interference using dsRNA-awd distorts adult wings and causes nymphs mortality in Diaphorina citri Kuwayama, the vector of citrus greening disease

Citrus greening is a distractive disease and causes great economic losses to citrus groves worldwide. Asian citrus Psyllid (ACP), Diaphorina citri, is the main vector of the bacterium causal agent, Candidatus Liberibacter asiaticus. The management of ACP will indubitably prevent the spread of this disease. RNA interference (RNAi) is a promising technique to explore gene functions as well as control pests. In this study, silencing abnormal wing disc (awd) gene which related with the development of wings in insects was investigated. Gene expression using qRT-PCR showed that transcription of awd is development-dependent and the highest level was found in the fifth (the last) instars of nymphal stage.  dsRNA-awd was applied to this instar using micro-application. Highly significant nymph mortality and wing abnormality of emerged adults were recorded.  Various forms of adult wing malformation were observed. There was a positive correlation between the percentage of wing-malformed adults and dsRNA concentration. Down-regulation of awd was found in adults that developed from dsRNA-awd treated nymphs. Significant down-regulation was required to induce wing-malformed phenotype. No effects was found when dsRNA-gfp or RNA-free water were used indicating the specific effect of dsRNA-awd. We have explored the implication of awd products in wing development, and our results strongly suggest that awd could be a potential target for insect management either via direct application of dsRNA or via citrus plants expressing dsRNA against the awd gene.