BmINR and BmAC6 genes involve in diapause regulation via the insulin/IGF signaling pathway in the silkworm (Bombyx mori)

Bingyan Fan  ¹ , Yanhua Chen  ¹ , Ayinuer Yasen  ¹ , Sai Wu  ¹ , Meixian Wang  ² , Juan Zhu  ¹ , Jinshan Huang  ¹ , Shunming Tang  ¹ , Xingjia Shen  ³

Affiliations

Affiliations

• ¹ Jiangsu Key Laboratory of Sericultural Biology and Biotechnology, College of Biotechnology, Jiangsu University of Science and Technology, Zhenjiang 212100, Jiangsu, China; Key Laboratory of Silkworm and Mulberry Genetic Improvement, Ministry of Agriculture and Rural Affairs, Sericultural Research Institute, Chinese Academy of Agricultural Sciences, Zhenjiang 212100, Jiangsu, China.
• ² Jiangsu Key Laboratory of Sericultural Biology and Biotechnology, College of Biotechnology, Jiangsu University of Science and Technology, Zhenjiang 212100, Jiangsu, China; Key Laboratory of Silkworm and Mulberry Genetic Improvement, Ministry of Agriculture and Rural Affairs, Sericultural Research Institute, Chinese Academy of Agricultural Sciences, Zhenjiang 212100, Jiangsu, China. Electronic address: mxwang@just.edu.cn.
• ³ Jiangsu Key Laboratory of Sericultural Biology and Biotechnology, College of Biotechnology, Jiangsu University of Science and Technology, Zhenjiang 212100, Jiangsu, China; Key Laboratory of Silkworm and Mulberry Genetic Improvement, Ministry of Agriculture and Rural Affairs, Sericultural Research Institute, Chinese Academy of Agricultural Sciences, Zhenjiang 212100, Jiangsu, China. Electronic address: shenxjsri@163.com.

• PMID: 37423399
• DOI: 10.1016/j.gene.2023.147626

Abstract

Diapause of the silkworm (Bombyx mori) is an important ecological adaptation strategy regulated by multiple signaling pathways. As an evolutionarily conserved signaling pathway, the insulin/IGF signaling (IIS) pathway is essential in regulating lifespan, energy accumulation, and stress resistance in diapause insects. However, the regulatory mechanism of IIS on diapause in B. mori is still not fully understood. To investigate the role of the IIS pathway in regulating diapause, we first analyzed the transcription levels of the insulin receptor (BmINR) and its downstream gene adenylate cyclase 6 (BmAC6). The diapause-terminated eggs of a bivoltine strain QiuFeng (V²-QF) were incubated at 25 °C in natural room light for preparing diapause egg producers (DEPs) and at 17 °C in total darkness for preparing non-diapause egg producers (NDEPs), respectively. Then we investigated the effects of BmINR and BmAC6 on diapause phenotype and expression of diapause-related genes by RNA interference (RNAi) and overexpression techniques. The results showed that the mRNA expression levels of BmINR and BmAC6 in the head and ovary of NDEPs were higher than those in DEPs during the early and middle pupal stages. Furthermore, when BmINR was knocked down in the NDEPs, approximately 14.43% of eggs were in light red color and subsequently changed into gray-purple color after 48 h post-oviposition, then stayed in a diapause state. On the other hand, overexpression of BmINR or BmAC6 via recombinant baculoviruses did not cause any obvious phenotypic alterations in NDEPs, but it upregulated the expression of genes related to carbohydrate metabolism, which provides energy for embryonic growth and development. Therefore, it can be concluded that BmINR and BmAC6 genes regulate embryonic diapause in bivoltine B. mori.

Keywords: Baculoviruse; BmAC6; BmINR; Bombyx mori; Embryonic diapause; Insulin/IGF signaling pathway.