RNAi mediated knockdown of the ryanodine receptor gene decreases chlorantraniliprole susceptibility in Sogatella furcifera.

The diamide insecticides activate ryanodine receptors (RyRs) to release and deplete intracellular calcium stores from the sarcoplasmic reticulum of muscles and the endoplasmic reticulum of many types of cells. They rapidly interrupt feeding of the target pest and eventually kill the pest due to starvation. However, information about the structure and function of insect RyRs is still limited. In this study, we isolated a 15,985bp full-length cDNA (named SfRyR) from Sogatella furcifera, a serious rice planthopper pest throughout Asia. SfRyR encodes a 5140-amino acid protein, which shares 78-97% sequence identities with other insect homologues, and less than 50% identities with Homo sapiens RyR1-3. All hallmarks of the RyR proteins are conserved in SfRyR. In the N-terminus, SfRyR has a MIR domain, two RIH domains, three SPRY domains, four copies of RyR repeated domain and a RIH-associated domain. In the C-terminus, SfRyR possesses two consensus calcium ion-binding EF-hand motifs, and six transmembrane helices. Temporal and spatial expression analysis showed that SfRyR was widely found in all development stages including egg, first through fifth instar nymphs, macropterous adult females and males. On day 2 fifth-instar nymphs, SfRyR was ubiquitously expressed in the head, thorax and abdomen. Dietary ingestion of dsSfRyR1 and dsSfRyR2 significantly reduced the mRNA level of SfRyR in the treated nymphs by 77.9% and 81.8% respectively, and greatly decreased chlorantraniliprole-induced mortality. Thus, our results suggested that SfRyR gene encoded a functional RyR that mediates chlorantraniliprole toxicity to S. furcifera.