Identification, mRNA expression, and functional analysis of chitin synthase 2 gene in the rusty grain beetle, Cryptolestes ferrugineus

Abstract

The insect midgut peritrophic membrane (PM) is a functional layer that protects insects against abrasive food particles and microorganism infection. Chitin is an essential component of the PM, and its synthesis is catalyzed by chitin synthase 2 (CHS2). CHS2 plays a unique role in chitin synthesis in the PM and thus represents a potential target for eco-friendly pesticides. The chitin synthase 2 gene (CfCHS2) of the rusty grain beetle, Cryptolestes ferrugineus (Stephens), was identified and evaluated. The full-length open reading frame of CfCHS2 was 4428 nucleotides long, encoding 1475 amino acids. Phylogenetic analysis revealed that CfCHS2 clearly clustered with the group of CHS2 sequences from other insects. Real-time quantitative PCR analysis showed that CfCHS2 was expressed in all developmental stages, with the highest expression level in the adult stage and the lowest in the pupal stage. In the adult stage, CfCHS2 was most highly expressed in the abdomen, followed by the midgut. RNAi assay results showed that the larvae curled up and could not crawl normally after CfCHS2 silencing. The midgut tissue of the larvae subjected to RNAi treatment was observed by tissue section scanner and transmission electron microscope (TEM). The results showed that the PM of the larvae was absent after CfCHS2 gene silencing. These results suggest that CfCHS2 is a potential RNAi target for C. ferrugineus control.