Buprofezin delayed the molting of Pardosa pseudoannulata, a predatory enemy for insect pests, by suppressing chitin synthase 1 expression

Spiders, the major predatory enemies of insect pests in fields, are vulnerable to insecticides. In this study, we observed that the recommended dose of buprofezin delayed the molting of the pond wolf spider Pardosa pseudoannulata, although it had no lethal effect on the spiders. Since buprofezin is an insect chitin biosynthesis inhibitor, we identified two chitin synthase genes (PpCHS1 and PpCHS2) in P. pseudoannulata. Tissue-specific expression profiling showed that PpCHS1 was most highly expressed in cuticle. In contrast, PpCHS2 showed highest mRNA levels in the midgut and fat body. RNAi knockdown of PpCHS1 significantly delayed the molting of 12-days old spiderlings, whereas no significant effect on the molting was observed in the PpCHS2-silencing spiderlings. The expression of PpCHS1 was significantly suppressed in the spiderlings treated with buprofezin, but rescued by exogenous ecdysteroid ponasterone A (PA). Consistent with this result, the molting delay caused by buprofezin was also rescued by PA. The results revealed that buprofezin delayed the molting of spiders by suppressing PpCHS1 expression, which will benefit the protection of P. pseudoannulate and related spider species.