橘小实蝇体内RNA病毒鉴定及其与RNAi通路互作方式研究

RNAi is one of the key antiviral related immune pathways in insects, which present an intensive interaction with the insect RNA viruses. Accordingly, the interaction between RNAi pathway and RNA viruses are in different manner: the infection of RNA virus could induce the activity of RNAi pathway, or RNA virus could inhibit the activity of RNAi pathway for their own benefit. In addition, RNA virus could either induction or inhibition of RNAi pathway during different infection stages. Currently, there are some obstacles for using RNA virus and RNAi as the environmental friendly strategies in insect pest management, such as RNA virus normally with low virulence to pest and RNAi in silencing pest gene only with limited level. Therefore, in the proposed project, one of the key invasive insect pest species in agriculture Bactrocera dosarlis is chosen to exploring the RNA viruses through viral metagenomics, next the relation between RNAi and RNA virus are studied for searching the strategy of using the synergy of RNAi in silencing of key antiviral-immune-related genes and RNA virus in inducing RNAi pathway activity for providing basic understanding for B. dosarlis control in this aspect.

RNAi是昆虫重要的抗病毒免疫通路之一，与RNA病毒在长期进化中的互作关系尤为突出。目前的研究表明，在昆虫RNAi通路与RNA病毒实际的互作中，表现出两种不同的互作方式：即一些RNA病毒的侵染可诱导寄主RNAi通路的活性，而一些RNA病毒的侵染可抑制寄主RNAi通路的活性。同时，有些RNA病毒可在不同侵染阶段与寄主RNAi表现出不同的互作方式。RNAi和RNA病毒是害虫绿色防控潜在的策略，但如何提高RNA病毒对靶标害虫的致病力、以及增强dsRNA对靶标害虫基因干扰效率是目前存在的难点问题。因此，本项目以我国重要的农业入侵害虫橘小实蝇为研究对象，通过病毒宏基因组技术发掘害虫体内的RNA病毒，研究害虫RNA病毒与寄主RNAi通路互作的方式，并为利用RNAi抑制害虫肠道免疫基因及害虫RNA病毒诱导寄主RNAi通路活性的联合增效作用进而控制桔小实蝇提供理论基础。

桔小实蝇是重要的入侵性农业害虫，其寄主范围广泛,并在上个世纪扩散到全球。桔小实蝇的入侵行为及寄主广泛的特性使自身常常暴露于多种病原物中。因此，其极易受到病原物感染。本项目利用高通量测序技术在桔小实蝇种群中发现了8种新型RNA病毒，包括4种正链RNA病毒、2种负链RNA病毒和2种双链RNA病毒。对病毒源性小rna的分析表明，这些病毒大部分具有复制活性，并能触发宿主抗病毒RNAi反应。在桔小实蝇多个地理种群也检测到这8种病毒，表明这些病毒体和宿主之间存在强烈的相关性。此外，这些病毒主要在桔小实蝇成虫期呈现高滴度，还感染成虫期特定的组织，主要为中枢神经系统和肠道组织，可能影响寄主神经系统进而影响寄主行为和寄主对食物的消化吸收及抵御对外源病原物。此外，该项目还探索了8种病毒在宿主受到短期或长期逆境胁迫时的动态变化，结果显示，部分病毒的滴度在受到胁迫的桔小实蝇中发生了应答性变化，说明这些病毒在宿主抗逆胁迫中可能具有重要影响。这些病毒的发现和理化特性研究丰富了对RNA病毒物种多样性和病毒与昆虫宿主适应性的认识。