The role of salivary effector FoCA2 in modulating the interactions of the defense response of the kidney bean plant and the adaptability of Frankliniella occidentalis under dinotefuran exposure

Abstract

Frankliniella occidentalis (Pergande) is a horticultural pest known for its overwhelming destructive power. Our previous study showed that dinotefuran significantly inhibited the feeding behavior of F. occidentalis on kidney bean plants. However, why dinotefuran suppressed feeding in F. occidentalis is unknown. Here, we analyzed differences in gene expression in the head (containing salivary glands) of F. occidentalis with or without dinotefuran LC₂₅ stress using transcriptome sequencing. Eventually, a salivary protein gene belonging to the carbonic anhydrase (CA) family was obtained and named as FoCA2. The full-length cDNA of FoCA2 was obtained by cloning, and the role of FoCA2 in the F. occidentalis antidefense toward the kidney bean plant was investigated using RNA interference. The results showed that FoCA2 was highly expressed in the head of F. occidentalis and at the feeding stages (nymph and adult). Silencing FoCA2 significantly inhibited F. occidentalis feeding and decreased its fecundity and survival; activated jasmonic and salicylic acid signaling pathway-related genes and callose synthase genes; and induced callose accumulation. However, dinotefuran down-regulated the expression of FoCA2 thereby attenuating the suppression of plant defense responses by FoCA2, which ultimately reduced the adaptability of F. occidentalis. Taken together, our findings suggest that FoCA2 is a key effector protein involved in F. occidentalis feeding and host adaptation, providing a foundation for studying the interaction between F. occidentalis and its host plants, and providing insights into the role of dinotefuran on pests.