共生菌Wolbachia调控截形叶螨温度适应性的分子机制

Tetranychus truncatus is a dominant pest mite of many agricultural crops, including maize and cotton. The endosymbiont Wolbachia is widely spread in Tetranychus truncatus. Our previous research investigated that Wolbachia can manipulate host reproduction and environment adaptability. In particular, the endosymbiont Wolbachia in spider mite facilitates host adapting to severing environment under high temperature stress, whereas the underlying mechanism involved in this phenomenon is unclear. Using the methods of genetics, biology, high-throughput sequencing and gene function analyses, we will measure the titers, tissue distribution and vertical transmission efficiency of endosymbionts in spider mite under different temperatures, which facilitates to understand the relationship of endosymbionts and thermal environment. Then we will test whether infection of symbiotic bacteria affects temperature choice of spider mite or not and compare the effects of symbiotic bacteria on spider mite’s reproduction and fitness, elucidating the role of endosymbionts in spider mite adaptation to severe environment. Eventually, we are going to investigate the gene expression of spider mites artificially injected with Wolbachia under different temperatures to canvass genes mediated specifically by Wolbachia. It is propitious to unveil the molecular mechanisms of functions endosymbionts play in spider mites when they adapt to various environment. The results will contribute to clarifying the symbionts’ effect on host ecology in the context of global warming. Meanwhile, it will lay a foundation for understanding the genetics and the damage caused by the spider mite.

截形叶螨是我国玉米、棉花等多种重要农作物上的优势害螨，其体内普遍感染共生菌Wolbachia。前期研究发现Wolbachia改变截形叶螨的生殖及对环境的适应性，高温胁迫下Wolbachia提高截形叶螨的适合度，但共生菌在截形叶螨适应不同温度中的作用机制尚不清楚。本项目拟通过遗传学、生物学、转录组学和基因功能分析等手段，检测不同温度下截形叶螨共生菌的密度、组织分布及传播效率，明确共生菌与温度间的关系；比较不同温度下共生菌对叶螨的温度偏好性、生殖、适合度及种群增长等指标的影响，阐明共生菌在宿主适应不同温度中的作用；测定人工注射共生菌的叶螨在不同温度下的基因表达，验证基因功能，揭示共生菌调控宿主温度适应性的分子机制。研究结果有助于解析全球温度变化背景下共生菌对宿主生态的影响机理，为了解截形叶螨遗传和灾变机制奠定基础。

节肢动物共生菌在其宿主的生理、生态及进化中发挥重要作用。本项目研究了共生菌Wolbachia和Spiroplasma在我国重要害虫截形叶螨温度适应性中的作用及其分子机制。研究结果表明，共生菌Wolbachia和Spiroplasma主要分布于宿主生殖组织及唾液腺，在适宜温度条件下，2种共生菌通过母体向子代垂直遗传的方式在截形叶螨种群中稳定传播，共生菌和温度处理改变截形叶螨细菌群落组成、网络结构及群落构建过程；室内构建了遗传背景一致的4个不同共生菌感染截形叶螨品系，比较4个叶螨品系在不同温度（20、25、30、35℃）条件下的存活率，单感染Wolbachia或Spiroplasma的截形叶螨耐热性显著低于双感染Wolbachia和Spiroplasma与未感染的截形叶螨，表明单感染共生菌Wolbachia或Spiroplasma限制宿主的耐热性；虽然较高温度（30℃）可促进2种共生菌在宿主叶螨体内的快速复制，但高温（35℃）下长期饲养叶螨可导致其体内Wolbachia和Spiroplasma丢失，低温（20℃）降低Spiroplasma的密度和传播效率，而对Wolbachia无显著影响；高低温改变宿主个体内Wolbachia滴度，进而影响Wolbachia诱导的宿主胞质不亲和强度；使用自制热梯度仪检测4个截形叶螨品系的偏好温度，2个感染Wolbachia的截形叶螨品系比未感染Wolbachia的叶螨更偏好相对较低的温度，表明Wolbachia可能参与调控宿主的温度选择行为；比较转录组分析不同温度短期胁迫下4个不同共生菌感染的截形叶螨转录表达模式，热激蛋白基因（Hsp20，Hsp70和Hsp90）数量及表达水平在4个叶螨品系中存在显著差异。本项目初步揭示了共生菌Wolbachia或Spiroplasma对宿主叶螨温度适应性调控的分子机制，共生菌介导截形叶螨对温度胁迫的反应可能是共生菌感染模式、温度偏好行为调节和转录调控等共同作用的结果。研究结果有助于解析全球气候变化背景下害虫的暴发机制，为害虫的绿色防控提供理论指导。研究结果发表论文6篇，培养研究生4名。