烟粉虱内共生细菌Hamiltonella对寄主有性生殖的调控

Symbionts are widespread in insects, they often play a role in manipulating host reproduction; however, the patterns and mechanisms of the manipulations are yet poorly understood. The whitefly Bemisia tabaci is a complex consisting of >36 putative cryptic species that reproduce in the mode of arrhenotoky. Among the complex, two cryptic species named as MEAM1 and MED, have invaded many regions of the globe in the past 30 years and caused enormous losses to crop production. Extensive field surveys have shown that the invasive populations of these two whiteflies harbour a particular endosymbiont named Hamiltonella, which has not been detected in any indigenous whiteflies. Preliminary laboratory experiments suggest that Hamiltonella exerts important impact on the reproductive activities of the two whitefly species; in particular loss of this symbiont or reduction in its density incurs reduction of fecundity and rapid decline of female ratio in their offspring. In this proposal, we will first further investigate the impact of Hamiltonella on the reproduction of the two whiteflies and reveal the pattern of impact, using a range of techniques including high temperature and antibiotic treatments. Next, we will focus our research efforts, using multidisciplinary approaches and modern microscopy, on the relationships between Hamiltonella and whitefly reproduction. Our objectives are to unravel the pattern and mechanisms of the impact of Hamiltonella on host production, and ultimately promote the understanding of mechanisms of whitefly invasions and provide the scientific basis for the development of novel technology for the management of this type of insect pests.

共生菌对寄主昆虫的生殖调控是一种常见现象，但调控规律及机理尚有许多未解之谜。烟粉虱是一个包含至少36个推测隐存种的复合群，营产雄孤雌生殖。该复合群中的MEAM1、MED两个隐存种，近30年来广泛入侵世界各地并给作物生产带来巨大损失。广泛野外调查表明，这两种入侵烟粉虱具有共生菌Hamiltonella(H)，而各地土著烟粉虱尚未发现带有该菌。室内实验初步表明，H菌对MEAM1、MED两个隐存种的生殖活动有重要影响，该菌的缺失或密度降低可使烟粉虱种群生殖力下降，后代中个体雌性比急剧降低。本项目计划在此基础上，综合应用高温处理和抗生素处理等方法，首先验证高温去除烟粉虱体内H菌对寄主生殖的影响，探讨影响规律；然后综合应用多学科的原理和方法和现代显微技术，集中探讨H菌与烟粉虱生殖的关系，旨在深入揭示该菌对寄主生殖调控的过程和机理，深化有关烟粉虱入侵机制的了解，并为发展烟粉虱防控的新方法提供科学基础。

Hamiltonella是世界性重要作物害虫中多种烟粉虱的次生共生菌，但有关该菌的生物学功能、特别是该菌能否调控寄主的有性生殖知之甚少。本项目通过广泛的田间调查，明确了该菌在入侵烟粉虱MED种群中的分布和感染频率，然后在室内构建了（1）特定的高温程序和（2）特定的抗生素组合两套有效去除烟粉虱体内Hamiltonella菌的方法，然后利用上述两套方法，分别获得了两个不带Hamiltonella菌的烟粉虱品系。利用这两个特有品系和正常品系进行的系列实验研究结果表明，Hamiltonella菌的缺失不影响烟粉虱雌雄个体的交配行为和授精，也不影响的卵的存活和发育，但卵基本不能正常受精，从而绝大多数的卵都是单倍体，都发育成雄性后代，导致不带Hamiltonella菌的烟粉虱品系的雌性比从正常的50-60%暴跌到5%以下，进而很快灭绝。这是首次证明，共生菌Hamiltonella是烟粉虱进行正常两性生殖的必要条件，其在烟粉虱生物学中的功能相似于一个原生共生细菌。不带这个菌，相应的烟粉虱种群就不能延续繁衍。研究结果不仅显著提升了人们有关该菌与寄主共生关系的认知，并为探究通过干扰该共生菌的传播来控制害虫危害提供了理论基础。.此外，利用项目实施过程中提供的机遇，另在烟粉虱共生菌在寄主代别间传播、一种新发现的共生菌对寄主昆虫传播植物病毒的作用、共生菌与寄主协同进化等与主题相关的研究中取得了创新性结果。

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