环境温度和保幼激素通过热休克因子协同调控棉铃虫卵黄蛋白原表达的分子机制

Juvenile hormone not only maintains insect larval stage, but also promotes adult reproduction. In many insects like Helicoverpa armigera, vitellogenin (Vg) synthesis is triggered by JH and also influenced by temperature. However, the molecular mechanisms of temperature and JH regulation of Vg expression remain elusive. Previous studies found that temperature and JH likely activate heat shock factor (HSF) phosphorylation via membrane signaling pathways involving PKA to up-regulate Vg transcription. But again, the underlying molecular mechanism is poorly understood. Here we aim to: (1) reveal the responsiveness of HSF phosphorylation to temperature and JH, identify HSF phosphorylation sites, and explore key factors and signal transduction pathways upstream of PKA involved in the regulation of HSF phosphorylation; (2) identify the HSE element in Vg promoter bound by phosphorylated HSF under the induction of temperature and JH, and elucidate the Vg transcriptional regulation by HSF. By combining the environmental factors and endocrine hormone, this study will provide new insights into our understanding in the regulation of insect fecundity and the reproductive adaptation to environmental change.

保幼激素（JH）不但维持昆虫幼虫状态，也促进成虫生殖。以棉铃虫为代表的许多昆虫中，卵黄蛋白原（Vg）的合成由JH激发，并受环境温度的影响，但对环境温度和JH协同调控Vg合成的分子机制缺乏了解。本项目前期研究发现，环境温度和JH可能通过包括PKA在内的膜信号通路激活热休克因子（HSF）的磷酸化，进而上调Vg转录，但其中的分子机制有待深入阐明。基于前期研究基础和文献报道，本项目以棉铃虫为模式，拟开展以下研究：（1）探明HSF磷酸化对环境温度变化和JH的响应机制，鉴定HSF的磷酸化位点，解析PKA上游参与催化HSF磷酸化的关键因子和信号转导途径；（2）明确环境温度和JH共同作用下，磷酸化HSF结合Vg基因启动子的HSE元件，阐明HSF对Vg转录的直接调控。研究结果将综合环境因子和内分泌激素，丰富对昆虫生殖力调控和环境变化生殖适应机理的了解。

昆虫的产卵量与环境温度密切相关，当环境温度升高到一定程度时，昆虫才会启动卵黄蛋白原Vg的表达，而且在适宜温度范围内，昆虫产卵量随温度的升高而增加。以棉铃虫为代表的许多昆虫中，Vg的合成由JH调控，同时受环境温度的影响，但环境温度和JH如何协同调控Vg表达的分子机制尚不清楚。本项目以棉铃虫为研究对象，发现HSF参与温度和JH信号通路调控Vg表达；而且，环境温度升高诱导HSF上调表达，JH通过PKA介导HSF磷酸化修饰（磷酸化位点为Ser-574）；磷酸化的HSF结合棉铃虫Vg启动子的HSE3元件，进而促进Vg转录。本项目的研究结果将环境因子和内分泌激素整合，不仅丰富了对昆虫生殖力调控和环境变化生殖适应机理的了解，而且为害虫的绿色防控提供了基础。