CHS-2 Is Involved in the Response of Aedes albopictus (Diptera: Culicidae) Larvae to Cadmium Stress by Mediating the Formation of the Peritrophic Membrane

Pollution with heavy metals, such as cadmium (Cd), can significantly affect insect growth, development, and behavior. The midgut is an essential organ for stress response. <i>Chitin synthase-2</i> (<i>CHS-2</i>) is closely associated with forming the peritrophic membrane (PM). The fourth-instar larvae of <i>Aedes albopictus</i> were exposed to varying concentrations of Cd. The results showed that Cd inhibited chitin synthesis and metabolism-related genes, but thickened the midgut PM, indicating that the larvae could respond to Cd stress through the midgut PM. Silencing <i>CHS-2</i> by RNA interference resulted more severe vacuolization and malformation of midgut epithelial cells without midgut PM protection. Additionally, there was an intensified redox reaction, upregulated expression of metallothionein (MT) and heat shock proteins 70 (HSP70), and increased activity of antioxidant enzymes at some scattered time points. This study confirms that <i>CHS-2</i> is involved in oxidative stress induced by Cd exposure by regulating PM formation. This study also contributes to further understanding the resistance mechanism of <i>Ae. albopictus</i> under Cd stress, thereby establishing a theoretical foundation for the future studies of them, which is concerned with the possibility of <i>Ae. albopictus</i> as a water environment detection and the control of <i>Ae. albopictus</i> based on resistance mechanism.