烟粉虱内共生菌Rickettsia的水平传播途径及其分子机制研究

Innumerable species of insects are associated with various intracellular bacterial endosymbionts. These endsoymbionts usually provide essential nutrients under limited or unbalanced diets to their hosts, manipulating host reproductive systems through a variety of strategies, and can also increasing the defensive ability of their host against thermal stress, natural enemies and pathogens. Earlier studies revealed that secondary endosymbionts are maternally inherited and vertical transmitted among different generations, however, the occurrence of closely related stains of maternally transmitted endosymbionts in distantly related arthropod species indicated that a means of horizontal transmission might exist...Here, we focus the interactions of the most devastating invasive pest, whitefly Bemisia tabaci, and its endosymbiont Rickettsia. The horizontal transmission routes of Rickettsia between different whitefly populations, including host plant mediated, parastitoid mediated and sex mating are investigated, using PCR, FISH, transmission electron microscope and multiple gene analysis and insect physiology methods. ..The expected findings will benefit us to deeply understand the transmission approach of endosymbionts, to verify our hypothesis of “plant, parasitoid and sex mating behavior mediated horizontal transmission of endosymbionts”, will also help us to evaluate the pros and cons of endosymbionts in pest management. Results are expected to be much significant in the exploration and development of novel strategies for pest prevention and integrated control.

自然界中昆虫与细菌共生现象广泛存在。内共生菌可以向寄主提供必要的营养物质、调控寄主生殖方式、增强寄主对环境的适应力以及对病原菌或天敌的抵抗力。本项目以重大农业入侵害虫烟粉虱Bemisia tabaci及其次生共生菌Rickettsia为研究对象，利用昆虫生理学、PCR、荧光原位杂交、扫描电镜以及MLST分型等分子生态学技术，研究以烟粉虱为代表的刺吸式昆虫体内Rickettsia次生共生菌通过寄主植物、寄生蜂及两性交配途径进行水平传播的过程及其分子机制，验证“昆虫共生菌三种水平传播途径”假说。本项目的预期研究成果，可以诠释“次生共生菌在自然界中普遍存在”以及“次生共生菌与昆虫寄主之间存在非协同进化关系”的原因，丰富人类对共生菌传播机制的认知；也可为今后利用Rickettsia、Wolbachia等昆虫内共生菌开展农业昆虫的控害保益、探索烟粉虱等重大农业害虫的新型防控策略与技术提供重要参考。

自然界中内共生菌可以向其昆虫宿主提供食物中缺乏营养物质、调控宿主生殖方式、增强宿主防御病原菌或天敌寄生的能力等。本项目以入侵害虫烟粉虱及其次生共生菌Rickettsia为研究对象，研究了以烟粉虱为代表的刺吸式昆虫体内Rickettsia次生共生菌的水平传播途径及其机制，进一步诠释了“次生共生菌在自然界中普遍存在”以及“次生共生菌与昆虫寄主之间存在非协同进化关系”的原因。. . 主要研究结果如下：（1） 棉花、烟草、芥蓝、番茄、一品红等不同寄主植物上烟粉虱体内Rickettsia含量存在明显不同，以一品红、芥蓝和棉花等多汁作物上的烟粉虱种群体内含量最高；（2）创建了“单对继代饲养筛选既定烟粉虱内共生菌的新方法；（3）烟粉虱寄主植物、寄生蜂对烟粉虱的取食与产卵刺探、烟粉虱的两性交配均可以介导Rickettsia内共生菌在B型烟粉虱不同种群之间进行水平传播；（4）Rickettsia进入新的植物宿主之后，存在明显的分布与消长动态，并能够激发植物宿主的防御反应、影响植物住宿的营养代谢；（5）丽蚜小蜂介导转染的Rickettsia可以在B型烟粉虱后代垂直传播，Rickettsia的转染（短暂或长期）对丽蚜小蜂和烟粉虱体内的营养物质含量都有较为显著的影响；（6）水平传播转染的Rickettsia内共生菌对烟粉虱生长发育、繁殖、抗逆性及抗药性等均有明显的积极的影响，烟粉虱子代种群存活率和繁殖量都明显上升，并增强了烟粉虱的抗药性、防御寄生蜂寄生的能力；（7）在寄主植物与寄生蜂的介导下，Rickettsia可以在B型与Q型烟粉虱种群之间进行水平传播。研究成果为今后从昆虫内共生菌的角度出发，开展农业昆虫的控害保益、探索烟粉虱等重大农业害虫的新型防控策略与技术提供了重要参考。