Identification of a Chitin Synthase Gene from Arma chinensis (Hemiptera: Pentatomidae) Under Temperature Stress

Chitin synthase (CHS) is essential for maintaining exoskeletal integrity and environmental adaptability in insects. CHS genes are categorized into two types, CHS1 and CHS2. Hemipteran insects possess only the CHS1 gene due to the absence of a peritrophic matrix (PM) in their midgut. However, the identification and functional characterization of the CHS1 gene in Pentatomidae species have not been reported. This study reports the first identification of a CHS gene, ArmaCHS1, from the predatory stink bug, Arma chinensis, and investigates its role in response to temperature stress. The ArmaCHS1 open reading frame spans 4407 bp, encoding a protein of 1468 amino acids, with 14 transmembrane helices and seven N-glycosylation sites. Phylogenetic analysis confirmed its classification within the CHS1 clade, closely related to CHS1 from Halyomorpha halys. qRT-PCR analysis revealed that ArmaCHS1 is predominantly expressed in the exoskeleton and displays developmentally regulated expression (lowest in eggs, highest in adults). Temperature stress experiments demonstrated that ArmaCHS1 expression was significantly upregulated at low temperatures (12 °C, 19 °C) and markedly downregulated at high temperatures (33 °C, 40 °C). These findings indicate that ArmaCHS1 likely contributes to thermal adaptation in A. chinensis by modulating chitin biosynthesis, providing new insights into the environmental stress responses of beneficial predatory insects.