RNA interference against gut osmoregulatory genes in phloem-feeding insects

In planta RNAi (i.e. plants engineered to synthesize active RNAi molecules) has great potential as a strategy to control insect crop pests. This study investigated the impact of RNAi against osmoregulatory genes expressed in the gut of two phloem-feeding species, the green peach aphid Myzus persicae and the potato/tomato psyllid Bactericera cockerelli. The target genes comprising candidate gut sucrase, aquaporin and sugar transporter genes were identified by mining insect genomic and transcriptomic datasets for genes orthologous to empirically-tested osmoregulatory genes of the pea aphid Acyrthosiphon pisum. Insects feeding on plants with RNAi against the target genes exhibited elevated hemolymph osmotic pressure (a predicted effect of perturbed osmotic function) and some reduction in performance, especially offspring production in M. persicae and mortality in B. cockerelli, associated with up to 50% reduction in mean expression of the target genes. The effects were particularly pronounced for insects treated with RNAi against multiple osmoregulatory genes, i.e. combinatorial RNAi, suggesting that the partial silencing of multiple genes with related roles can yield greater functional impairment than RNAi against a single gene. These results demonstrate the potential of RNAi against osmoregulatory genes, but further advances to improve the efficacy of RNAi in phloem-feeding insects are required to achieve effective pest control.