异色瓢虫生殖滞育准备中体内低水平保幼激素的维持机制

Exploration of insect diapause mechanism at the molecular level is of great significance in revealing the molecular bases of insect ecological adaptations, extending the shelf-life of natural enemy insects and providing innovation on pest management strategies. Generally, absence of juvenile hormone (JH) is the main reason for insect reproductive diapause. However, we still don’t know whether the block of JH biosynthesis or the increase of JH degradation or both the two pathways lead to the low JH titer. Previous studies have shown that predatory beetle Harmonia axyridis still enter reproductive diapause when they eat JH-rich aphids during diapause preparatory period, suggesting that absence of JH during the diapause preparation of H. axyridis may rely on both the regulations of JH biosynthesis and degradation. Therefore, H. axyridis is an ideal model for diapause study concerning the regulation of JH titer during diapause preparatory period. In current project, we plan to measure the JH titer in H. axyridis after feeding with or without JH-rich food, and then ensure the essential roles of both the regulations of JH biosynthesis and degradation in diapause preparation by combining with RNA-seq analysis. By using quantitative PCR and RNA interference techniques, we will investigate the dynamic profiles and regulatory mechanisms of JH biosynthesis and degradation during diapause preparatory period of H. axyridis. Our results will reveal the endocrine mechanism of reproductive diapause, provide new insights into the evolution of feeding adaptations of predatory beetles, and support the use of natural enemy insects by extending their shelf-life.

理解滞育调控的分子机制对揭示昆虫的生态适应基础、延长天敌昆虫货架期和创新害虫防控策略具有重要意义。一般认为，昆虫生殖滞育是因保幼激素JH缺乏而引起。然而，我们并不清楚JH的缺乏是依赖于其合成受阻还是其降解加剧或二者并存。申请人前期发现，捕食性天敌异色瓢虫在滞育准备期，取食富含JH的猎物蚜虫后仍可进入生殖滞育。这说明异色瓢虫成虫可能不仅通过下调JH合成，还可能通过加速JH降解来完成滞育准备。因此，异色瓢虫是研究滞育准备中JH含量调节机制的理想模型。本项目拟通过测定滞育准备期异色瓢虫取食有或无JH的食物后其体内JH含量变化，结合RNA-seq明确异色瓢虫通过调控体内JH合成与降解两条途径来进入滞育；利用定量PCR和RNAi等技术，探明异色瓢虫在滞育准备期JH合成与降解的动态变化和调控机制。项目研究不仅能深化生殖滞育的内分泌调控机制、窥探捕食性天敌的食性进化，还可为天敌昆虫货架期的延长提供指导。

理解滞育调控的分子机制对揭示昆虫的生态适应基础、延长天敌昆虫货架期和创新害虫防控策略具有重要意义。一般认为，昆虫生殖滞育是因保幼激素JH缺乏而引起。然而，我们并不清楚JH的缺乏是依赖于其合成受阻还是其降解加剧或二者并存。本项目通过给注定滞育个体添饲外源JHA结合RNAi干扰注定非滞育给他JH核受体Met测定滞育表型，证明了JH缺乏是异色瓢虫生殖滞育的关键原因。通过对取食有无JH食物的注定滞育和非滞育个体进行RNA-seq筛选出了参与调控滞育准备期JH水平降低的关键候选基因。结合RNAi技术对候选基因进行了验证，结果表明异色瓢虫滞育准备期通过同时降低JH合成并促进JH降解来维持体内低水平JH，其中JH合成降低对滞育准备期低水平JH起决定性作用。对JH合成途径上游调控因子的进一步探究结果显示，DNA甲基转移酶关联蛋白1（DMAP1）可通过抑制JH合成来抑制注定非滞育个体的生殖发育，表明DNA甲基化水平的差异可能是JH合成途径的上游调控因子。研究结果揭示了捕食性天敌昆虫生殖滞育的内分泌调控机制，可为天敌昆虫货架期的延长提供指导。