植食性昆虫唾液效应子和激发子的研究进展

Research advances of salivary effectors and elicitors in herbivorous insects

植食性昆虫与寄主植物通过协同进化形成了复杂的防御和反防御机制。本文系统综述了昆虫唾液效应子和激发子在植物与昆虫互作中的作用及机理。昆虫取食中释放的唾液激发子被植物识别而激活植物早期免疫反应,昆虫也能从口腔分泌效应子到植物体内抑制免疫;抗性植物则利用抗性(R)蛋白识别昆虫无毒效应子,启动效应子诱导的免疫反应,而昆虫又进化出多种方式来躲避植物R蛋白的识别。总之,在这场军备竞赛中,昆虫的唾液成分决定着昆虫能否取食成功。取食过程中,咀嚼式口器害虫分泌大量酶类到植物体内,而刺吸式害虫则分泌胶状和水样唾液到植物中,它们都利用激发子和效应子去调控植物的免疫防御反应。分析现已报道的昆虫效应子发现其作用机制各有不同,具体表现为影响植物早期防御信号,调控植物激素通路及其他通路,或靶向小分子RNA通路。本文还综述了昆虫激发子的最新进展,揭示激发子可以通过诱导释放植物次生代谢物以及调控激素水平、Ca^(2+)内流和活性氧爆发增强植物抗性。最后对昆虫效应子的分泌特性、寄主特异性和多功能性作了分析,并对无毒效应子及其对应的植物R基因,以及激发子的模式识别受体的研究进行了展望。

Herbivorous insects and host plants have developed complicated defense and counter defense mechanisms through co-evolution.In this article,we systematically reviewed the roles of insect saliva effectors and elicitors in the interactions between insects and plants and their mechanisms.The salivary elicitors secreted by insects during feeding can be recognized by plants to trigger early plant immunity,while insect effectors released from oral secretion can inhibit plant immune defenses.Resistant plants further evolved R proteins to recognize insect avirulence effectors and initiate effector-triggered immunity.Phytophagous insects can avoid the recognition by plant R proteins through different strategies.Therefore,in this arms race,insect saliva determines whether insects can succeed to feed on plants.During feeding process,chewing insects secrete a large number of enzymes into plants,and piercing-sucking insects secrete sheath saliva and water saliva into plants,but both of them utilize effectors and elicitors to manipulate plant immune responses.By analyzing the reported insect effectors,it was found that the molecular mechanisms of insect effectors are different.They affect plant early defense signals,regulate plant hormone pathways or others,or target small RNA pathways.Recent advances in insect elicitors were also reviewed in this article,revealing that elicitors can induce the release of plant secondary metabolites,and regulate hormone levels,Ca^(2+) influx and reactive oxygen species(ROS)burst to enhance plant resistance.Finally,we analyzed the secretory characteristics,host specificity and multifunctionality of insect effectors,and discussed research prospects on avirulence effectors and their plant R genes as well as pattern recognition receptors of elicitors.