入侵生物马铃薯甲虫肠道微生物对寄主植物抗虫防御的调控及其机理

Colorado potato beetle (CPB, Leptinotarsa decemlineata) is a very important destructive pest worldwide. After its invasion to Xinjiang Autonomous Region this pest has caused huge losses of potato yield together with the increasing risk of further dispersal and spreading to inland. Gut-associated microbes are treated as significant organs of insects, and interact and co-evolve with their host-insects. Our previous work showed that gut microbes played a key role in regulating plant induced defenses, but there is little information about the role of gut-associated microbes in the manipulation of invasive process of CPB. This study will investigate the gut microbes of invasive CPB using the methods of 16S rRNA sequencing, metagenome analysis and traditional bacterial isolation and identification. We will compare the differences in the diversity and abundance of gut microbes of CPB colonies between the native region United States and introduced region Xinjiang, and figure out the distinct bacterial isolates. Then the function of these different bacterial isolates in mediating the resistance and induced defenses of potato plants to insects will be determined. Fluorescence in situ hybridization will be used to observe the location of target bacterial strains, and the relative quantities of these bacteria on leaves or in insect inner organ will be examined by quantitative real time PCR. This study will test the hypothesis whether or not the gut-associated microbes play a key role in assisting CPB to adapt to the host-plant defense system to facilitate its invasion to new regions. The results will highlight the novel mechanism of CPB invasion and important ecological role of gut microbes, thus will provide a new guideline for invasive pest management.

马铃薯甲虫是国际公认的马铃薯毁灭性害虫，入侵我国新疆地区后，对我国马铃薯产业构成了严重的威胁，且其进一步扩散的风险正在加剧。肠道微生物是昆虫重要的组成部分，与宿主昆虫相互合作、协同进化。课题组前期研究表明，肠道微生物参与调控了植物的抗虫性，但目前还不知道其是否介导马铃薯甲虫的生物入侵。本项目拟以入侵我国的马铃薯甲虫为主要研究对象，利用16S rRNA扩增子测序、宏基因组测序以及传统培养法对其肠道微生物进行分离鉴定，分析比较美国原产地与入侵地新疆马铃薯甲虫肠道微生物种类和丰度的差异，测定肠道差异菌株对马铃薯植株抗虫能力和防御反应的影响，再利用荧光原位杂交技术和荧光定量PCR技术验证肠道差异菌株存在的部位和含量，从而揭示肠道微生物可能协助马铃薯甲虫在新的入侵地适应寄主植物抗性加剧生物入侵的机制，进一步阐明昆虫生物入侵机制和昆虫肠道微生物的生态学功能，为入侵生物马铃薯甲虫的综合防控提供新的策略。

马铃薯甲虫（Leptinatarsa decemlineata, Say）是国际公认的重大毁灭性害虫，20世纪90年代初传入我国新疆，已被列入进出境植物检疫有害生物名单。马铃薯是我国第四大粮食作物，马铃薯甲虫入侵后，已对当地马铃薯的生产造成了严重的经济损失。马铃薯甲虫能够迅速在新的入侵地对马铃薯造成危害，显示出其超强的适应能力。昆虫的多样性以及超强的行动能力在一定程度上与其共生微生物有着密不可分的关系，要全面理解昆虫生活史，对共生微生物的研究必不可少。马铃薯甲虫入侵到新疆以后，环境、寄主植物等因素势必会引起昆虫肠道微生物群落发生重要的变化，但肠道微生物的变化是否对马铃薯甲虫入侵和扩散产生影响还没有引起广泛的关注。本项目主要研究不同地理种群马铃薯甲虫肠道微生物及其调控寄主植物诱导抗性的差异，结果显示乌鲁木齐马铃薯甲虫较伊犁马铃薯甲虫能够更好地适应马铃薯植株的防御反应，并且根据16S rRNA扩增子测序结果显示乌鲁木齐种群肠道微生物种类更加多样，其中Enterobacter sp.、Acinetobacter sp.等属的细菌相对丰度较高。此外，马铃薯甲虫所排泄的粪便中同样存在可以抑制植物诱导防御的菌株。本项目的研究结果表明共生微生物在马铃薯甲虫入侵过程中扮演着非常重要的角色, 特别是在调控寄主植物诱导抗性方面，研究丰富和拓展了马铃薯甲虫入侵机制，为今后利用微生物来调控马铃薯甲虫与寄主植物互作和进行害虫综合防治奠定理论基础。