昆虫口腔分泌物效应子及其在害虫防治中基于RNAi技术的应用展望

Effectors in insect oral secretions and their application prospects in pest control based on RNAi technology

昆虫口腔分泌物(oral secretion,OS),又称返吐液,是昆虫唾液腺分泌的唾液和肠道分泌物的混合液。昆虫取食寄主植物过程中,OS随之分泌至植物中,并影响植物的防御反应。RNA干扰(RNA interference,RNAi)是研究昆虫基因功能有价值的反向遗传学工具,也是目前最有可能应用于害虫防治的新技术。本文主要综述了昆虫OS对寄主植物防御的影响、昆虫OS效应子的鉴定和OS效应子基于RNAi技术在害虫防治中可行性及应用前景。昆虫OS对寄主植物防御的影响主要表现为干扰植物的茉莉酸信号通路、筛管阻塞、Ca^(2+)通路等防御反应,进而促进昆虫摄取食物。目前,昆虫OS效应子主要鉴定手段是通过昆虫唾液腺转录组分析和OS蛋白组分析;而已鉴定的OS效应子主要来源于刺吸式口器昆虫,在咀嚼式口器昆虫中的报道甚少;功能研究发现昆虫OS效应子在寄主植物中的表达会影响昆虫存活率、繁殖力和取食能力及昆虫和植物的其他重要生理指标,并通过鉴定OS效应子与植物防御机制的相互作用关系,进而证明OS效应子在昆虫与寄主植物关系中的重要性。基于RNAi技术,通过注射、饲喂和植物介导RNAi等方法在多种昆虫中产生了OS效应子基因下调和生长发育受影响的现象,由此说明OS效应子基因已具备作为RNAi靶标的条件。虽然目前研究尚处于实验室阶段,但已证明其应用于害虫防治方面具有一定的可行性。昆虫口腔分泌物是研究昆虫与寄主植物相互作用机制的新方向。最后,对OS未来潜在的研究方向进行了展望,以期对我国害虫防治的研究提供理论指导。

Insect oral secretion(OS),also known as vomit,is a mixture of saliva secreted by salivary glands and secretions secreted by guts in insects.During insect feeding on host plants,OS is secreted into plants and affects plant defense responses.RNA interference(RNAi)is a valuable reverse genetics tool to study insect gene function and also a new technology to be used in pest control.In this article,we mainly reviewed the effects of insect OS on host plant defense,the identification of insect OS effectors and the feasibility and application of OS effectors based on RNAi technology in pest control.Insect OS affects host plant defense mainly by interfering with jasmonic acid signaling pathway,sieve tube obstruction,and Ca^(2+) pathway and other defense responses in host plants,and then promotes insects to ingest food.At present,the main methods of identification of insect OS effectors are based on the transcriptomic analysis of insect salivary glands and proteomic analysis of OS.Most of the OS effectors have been identified from insects with sucking mouthparts,and less reported in insects with chewing mouthparts.The functional studies revealed that the expression of insect OS effectors in host plants can affect the survival rate,fecundity,and feeding ability of insects and other important physiological indexes of both insects and plants.By identifying the interaction between OS effectors and plant defense mechanisms,the roles of OS effectors in the relationship between insects and host plants have been further demonstrated.Based on RNAi technology,the expression levels of OS effector genes are down-regulated,and the growth and development are affected in many insects by microinjection-,feeding-,and plant-mediated RNAi using OS effector genes as targets,suggesting that OS effector genes could be used as RNAi targets.Although the studies are still in the laboratory stage,their application in pest control has been proven to be feasible in certain degree.Insect oral secretions are a new direction to study the interaction mechanism between insects and host plants.Finally,the future research directions of OS have been prospected,hoping to provide some theoretical guidance for studies of pest control in China.