Both farnesyl diphosphate synthase genes are involved in the production of alarm pheromone in the green peach aphid Myzus persicae

Farnesyl diphosphate synthase (FPPS) catalyzes the formation of FPP, providing the precursor for the biosynthesis of (E)-β-farnesene (EβF) in plants, but it is unknown if FPPS supplies the precursor for the biosynthesis of EβF, the major component of aphid alarm pheromone, though our previous studies support the hypothesis that EβF is synthesized by the aphid itself. Here, we used two cohorts of the green peach aphid Myzus persicae separately, reared on pepper plant and artificial diet to test the correlations among droplet emission, EβF quantity, and FPPS gene expression. It was found that the proportion of aphids emitting cornicle droplets and the quantity of EβF per milligram of aphid were both significantly different between the two cohorts, which were positively correlated with the expression of the two FPPS genes ( MpFPPS1/ 2) in M. persicae. These results were further confirmed by RNAi-mediated knockdown of MpFPPS1/ 2. Specifically, knockdown of MpFPPS1/ 2 imposed no significant cost on the survival of aphid but remarkably increased the number of offspring per aphid; most importantly, knockdown of MpFPPS1/ 2 significantly reduced the proportion of aphids emitting droplets and the quantity of EβF calculated as per the weight of aphid. Our results suggest that both FPPS genes are involved in the production of EβF in M. persicae and cornicle droplet emission is closely associated with the EβF release in the aphid.