Characterization of Chitin Synthase B Gene (HvChsb) and the Effects on Feeding Behavior in Heortia vitessoides Moore

SIMPLE SUMMARY: Heortia vitessoides Moore is a leaf-eating pest that affects Aquilaria sinensis. In the outbreak period, the leaves of Aquilaria sinensis can be eaten up in a short time, resulting in the death of trees and great economic losses. Chitin is the main component of insect cuticle, peritrophic membrane, and tracheal intima. Chitin synthesis in insects is a complex process that requires the cooperation of many enzymes. Chitin synthase is one of the key enzymes in the process. Chitin synthase is divided into two types: chitin synthase A gene (Chsa) and chitin synthase B gene (Chsb). Chsb is mainly responsible for the tissue synthesis of chitin in midgut peritrophic membrane. It was found that the expression of HvChsb was inhibited, the growth and development were abnormal, and the mortality rate was increased. These findings provide a reference for the prevention and control of the pest from the perspective of gene manipulation. ABSTRACT: The chitin synthase B gene is a key enzyme in the chitin synthesis of insect peritrophic matrix (PM), which affects insects’ feeding behavior. The chitin synthase B gene was cloned from the transcription library of Heortia vitessoides Moore. RT-qPCR showed that HvChsb was highly expressed in the larval stage of H. vitessoides, especially on the first day of the pre-pupal stage, as well as in the midgut of larvae and the abdomen of adults. After starvation treatment, HvChsb was found to be significantly inhibited over time. After 48 h of starvation, the feeding experiment showed that HvChsb increased with the prolongation of the re-feeding time. The experimental data showed that feeding affected the expression of HvChsb. HvChsb was effectively silenced via RNA interference; thus, its function was lost, significantly decreasing the survival rate of H. vitessoides. The survival rate from larval-to-pupal stages was only 43.33%, and this rate was accompanied by abnormal phenotypes. It can be seen that HvChsb plays a key role in the average growth and development of H. vitessoides.