The serine/threonine kinase CcAkt regulates the fertility of Coridius chinensis

Akt (also known as protein kinase B) belongs to the multifunctional serine/threonine kinase family and is an important component of the insulin signaling pathway that plays a key role in many biological processes such as cell growth, proliferation, and survival. However, few studies have reported the effect of Akt on reproduction in Hemiptera. In this study, we cloned and characterized the Akt gene from Coridius chinensis (CcAkt). The open reading frame of CcAkt has a length of 1,563 bp and encodes 520 amino acids. It has a conserved pleckstrin homology domain, a serine/threonine protein kinase catalytic domain, and a serine/threonine protein kinase domain. Phylogenetic analysis showed that CcAkt and HhAkt of Halyomorpha halys had the highest similarity. Analysis of temporal and spatial expression patterns revealed that CcAkt is expressed throughout development and in various tissues of C. chinensis adults. CcAkt expression was high in female adult and the fourth instar nymph stage of C. chinensis. In C. chinensis adult, CcAkt expression was highest in the testis and ovary. Injection of bovine insulin induced CcAkt expression, whereas that of 20-hydroxyecdysone significantly reduced CcAkt expression. Both hormones, however, induced the expression of vitellogenin (Vg) and vitellogenin receptor (VgR). In unmated females, CcAkt knockout resulted in decreased expression of CcVg and CcVgR, stunted the development of the ovarioles, decreased the number of eggs and hatching rate. These findings suggest that CcAkt may be involved in regulating the reproduction of C. chinensis.