胰岛素信号调控柑橘大实蝇蛹滞育转变的分子机制

Insulin/IGF signaling (IIS) is an important signal transduction pathway in animal ontogenetic processes, involving in nutrient synthesis and metabolism, cell proliferation and endocrine regulation. Bactrocera minax, a serious citrus pest in China, bridges winter seasons by means of pupal diapause. Treated with 20-hydroxyecdysone (20E), diapausing individual up-regulated insulin receptor substrate IRS gene expression and subsequently significantly up-regulated serine/threonine kinase Akt and rat sarcoma protein Ras, activating downstream molecules to accelerate metabolism and diapause termination. However, it remains unclear how IIS responds to exogenous stimuli and precisely manages its energy reserves to regulate diapause developmental processes. This project aims to clarify the role of IIS on B. minax signal transduction and diapause regulation. The transcriptional and transduction mode of IIS during diapause development will be analyzed and the function of key regulatory genes will be verified by using of RNAi and over-expression in vivo, as well as their acting trajectory to elucidate its regulating mechanism. It will unravel the function of IIS on B. minax pupal energy budget and diapause development to better understand the interaction of IIS with other pathways in diapause regulation network, which has great significance to insect diapause research and pest management.

胰岛素信号通路是调控动物生长发育的重要信号传导途径，参与机体营养合成与代谢、细胞增殖和内分泌调节。柑橘大实蝇以蛹滞育越冬，前期研究发现蜕皮激素20E处理滞育个体后，胰岛素受体底物IRS迅速上调表达，引起丝氨酸苏氨酸激酶Akt和Ras蛋白显著上调，活化下游信号分子促进代谢和滞育解除。然而胰岛素信号通路介导上下游信号传导和参与蛹滞育期能量代谢和滞育转变的分子调控制尚不明确。本项目拟克隆柑橘大实蝇胰岛素信号通路相关基因，通过靶基因干扰和体内过表达研究其调控作用，明确滞育调控的关键基因及其转录调控作用方式，解析胰岛素信号调控滞育发育的作用途径。项目的完成将有望阐明柑橘大实蝇胰岛素信号对环境信号应答及其参与介导昆虫的滞育调控网络，对昆虫滞育调控和害虫治理具有重要的理论和实践意义。

一化性昆虫柑橘大实蝇Bactrocera minax 是柑橘果树重要害虫，以蛹滞育越冬，次年成虫羽化，与寄主植物生长同步。其蛹滞育是引起成虫同步羽化、暴发成灾的前提，对其越冬和同步寄主生长极为重要。研究发现蜕皮激素20E处理滞育个体后，胰岛素信号显著上调，促进代谢和滞育解除，然而，胰岛素信号通路介导上下游信号传导和参与蛹滞育期能量代谢和滞育转变的分子调控制尚不明确。本项目利用分子生物学技术手段克隆柑橘大实蝇胰岛素信号通路相关基因，对不同时期滞育个体胰岛素信号通路基因进行表达模式分析，开展滞育期能量物质和激素检测，结果表明随着滞育发育进行，胰岛素信号逐渐增强，参与滞育期间能量代谢调节及20E生物合成。其中，筛选到1个特异性脑部表达的类胰岛素肽ILP1，沉默该基因表达能促进滞育解除。利用20E处理滞育个体后，结合组学分析和生化数据比较发现滞育解除与能量代谢显著关联，代谢改变（或中间代谢物变化）是促进滞育解除的主要因素。20E介导滞育解除不是单一依赖于其核受体（EcR/Usp）介导的基因组途径，同时依赖于其非基因组途径，由第二信使（如cAMP、Ca2+等）介导的快速反应，与胰岛素信号的Ras-MAPK途径（非PI3K-Akt途径）共同促进滞育解除。本研究探索了胰岛素信号介导的柑橘大实蝇滞育调控网络，对昆虫滞育调控和害虫治理研究具有重要理论价值和实践意义。