Akt regulates the fertility of Coridius chinensis by insulin signaling pathway

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 (PH), catalytic domain of serine/threonine protein kinases (S_TKc), and extension of Ser/Thr-type protein kinases (S_TK_X). 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 was highly expressed in the female adult and the fourth-instar nymph, as well as in the testis and ovary of C. chinensis. Injection of bovine insulin and methoprene induced the CcAkt expression, whereas that of 20-hydroxyecdysone significantly reduced the CcAkt expression. These three hormones, however, induced the expression of vitellogenin (Vg) and vitellogenin receptor (VgR). In unmated females, knockdown of CcAkt resulted in decreased expression of CcVg and CcVgR, stunted the development of the ovarioles, decreased the number of eggs and hatching rate. These findings from RNA interference experiment suggested that CcAkt may be involved in regulating the reproduction of C. chinensis.