CHS-2 is involved in the response of Aedes albopictus larvae to Cadmium stress by mediating the formation of peritrophic membrane

Abstract

Heavy metal stress can affect the growth, development and behavior of insects, Cadmium (Cd) is one of the most seriously polluted heavy metals. Midgut is the main organ for insects to cope with heavy metal stress. chitin synthase-2 (CHS-2) is mainly expressed in the midgut of insects, which is closely related to the formation of the peritrophic membrane (PM) in the midgut. This study vector insects Aedes albopictus as the object, the fourth-instar larvae were exposed to three different concentrations of Cd. The results showed that Cd inhibited the expression of genes related to chitin synthesis and metabolism, and thickened the midgut PM, indicating that the larvae of Ae. albopictus could respond to Cd stress through the midgut PM. Secondly, silencing CHS-2 by RNAi combined with three concentrations of Cd stress, in the absence of the protective effect of midgut PM, Cd stress will lead to more serious vacuolization and deformity of larval midgut epithelial cells, and more intense redox reaction of the insect body, the expression of MT, HSP70 and antioxidant enzyme genes increased, and the activity of antioxidant enzymes also increased at different times. This study confirmed that CHS-2 was involved in the oxidative stress induced by Cd stress by regulating the formation of PM in the midgut of Ae. albopictus, and clarified the resistance of Ae. albopictus to Cd stress and some of the internal mechanisms, which provided a theoretical basis for the related research of using Ae. albopictus to monitor the aquatic environment.