RNA interference: a promising natural mechanism for crop pest control

S Rahman, MGK Jones and J Fosu-Nyarko

Murdoch University, 90, South street, WA-6150

Aphids are a major class of insect pests of economically important crops: the losses they cause are from direct feeding damage and transmission of many viral diseases. For example, the Green Peach Aphid (GPA, Myzus persicae) can transmit about 50% of plant viruses, and honeydew secretions enable growth of sooty moulds on host plants. These polyphagous pests are becoming increasingly resistant to some pesticides hence there is a need to develop other methods to control them such as RNA interference (RNAi). Its efficiency depends on appropriate selection of target genes. Since the nervous system is an effective target for chemical control, genes encoding neuronal signalling molecules were chosen for study. Using bioinformatics twenty-four genes were chosen as potential targets for aphid control, and the effects of their down-regulation were assessed after oral delivery of double stranded RNA (dsRNA) or host induced gene silencing. Silencing of some target genes via artificial feeding resulted in paralysis, or inability to moult, reducing their survival and/or reproduction. The results from in vitro RNAi studies allowed selection of promising candidate genes and initial in vivo experiment was conducted. The expected output of this research is a series of target genes that if down-regulated via artificial feeding or transgenic plants will confer GPA resistance to crop plants. The power of RNAi is its flexibility and the fact that it functions at the transcriptional rather than protein level. It can be applied to control other important aphid species, and also other plant pests.