唾液蛋白在吡蚜酮抑制灰飞虱取食韧皮部汁液中的作用和机制

Pymetrozine is a valuable insecticide for control of sucking insects, including the small brown planthopper, Laodelphax striatellus, one of the most serious pests in Asia. The toxicity of pymetrozine is by feeding inhibition, but the action mechanisms and target are unclear. Previous studies found that pymetrozine had a strong inhibition to phloem ingestion of L. striatellus, and silencing some genes encoding the salivary proteins in sap-sucking insects had a similar effect. Based on the above, in order to explore whether and how pymetrozine inhibits the phloem feeding by altering the expression of salivary genes, and then significantly reduces the capacity of both virus acquisition and inoculation, we intend to discover the salivary genes that are down-regulated by pymetrozine treatment by combining the saliva proteome and the transcriptomes of salivary glands of L. striatellus treated by pymetrozine. After that, we study the roles of the above salivary proteins in phloem feeding, modification of rice defense response and transmission of rice black-streaked dwarf virus. The above research will not only be beneficial to discover new targets and create new effective pesticides, but also help us to explore new methods to control L. striatellus and virus disease.

吡蚜酮是防治包括灰飞虱在内的刺吸式口器害虫的重要杀虫剂之一，表现出显著的取食抑制效应，但具体作用机制和靶标并不清楚。前期研究发现，经吡蚜酮浸苗处理后，灰飞虱在韧皮部的摄食行为几乎被阻断，而沉默关键唾液蛋白的编码基因也会产生类似的韧皮部取食抑制效应，在此研究基础上，为进一步探索吡蚜酮是否以及如何改变唾液蛋白的表达来抑制灰飞虱对韧皮部汁液的取食，进而减弱其获取和传播病毒的能力。本项目拟结合灰飞虱的唾液蛋白组以及吡蚜酮对唾液腺转录组的影响，挖掘出一些能够被吡蚜酮抑制表达的唾液蛋白，并进一步解析相关唾液蛋白在灰飞虱取食韧皮部、影响水稻防御反应和传播水稻黑条矮缩病毒中的作用。完成本项目不仅有助于发掘新的杀虫靶标和创制新型农药，还会为灰飞虱及其传播病毒病的综合防治提供理论依据。

吡蚜酮处理显著抑制灰飞虱的取食和存活，但具体机理未知。我们首先采用定量蛋白组学技术，比较发现吡蚜酮处理可下调灰飞虱唾液腺中二硫键异构酶和钙离子结合蛋白等87种蛋白的表达。其中二硫键异构酶是灰飞虱取食、存活所必需的唾液蛋白，但也是一种激发子，能够诱导植物免疫；而钙离子蛋白通过阻断水稻的钙信号通路，有效制衡飞虱取食所诱导的植物防御，从而有利于灰飞虱的取食和存活；还发现繁殖相关蛋白-卵黄原蛋白作为唾液效应子发挥功能，可与水稻细胞核中免疫调控转录因子互作，削弱植物防御。因此吡蚜酮可通过改变唾液效应子的表达来抑制灰飞虱的取食。在此基础上利用效应子和水稻中的效应子互作蛋白辅助育种技术获得抗飞虱的转基因水稻材料。围绕灰飞虱效应子和水稻抗虫因子的发掘与利用，开展的这一系列研究，将有助于揭示唾液效应子在昆虫-植物互作、取食中的作用，为农药新靶标鉴定奠定基础。