番茄虫害诱导挥发物介导的斜纹夜蛾反防御机制

The magical interaction and co-evolution between plants and insects has always been an interesting scientific issue for scientists. Plants can be induced by infested herbivorous insects to produce toxic defensive compounds and release herbivore-induced plant volatiles (HIPVs) to prevent insect attack. Meantime, insect herbivores are able to use toxic compounds to induce detoxification enzymes to develop counter-defense. However, so far it is unknown whether or not herbivorous insects can develop HIPVs-mediated counter-defense. Our previous study has confirmed that tomato HIPVs enhanced larval resistance of tobacco cutworm, Spodoptera litura (Lep., Noctuidae, an important lepidopteran pest) against tomato defense. In this project, we will examine the effect of exposure of tobacco cutworm larvae to tomato HIPVs on detoxification of defensive compounds, larval growth, oviposition, and behavioral responses of the insect. Specific tomato volatile components responsible for HIPVs-induced detoxification will be identified by jointly using GC/MS and bioassays. Specific tomato volatile synthesis mutants will be generated by using CRISPR/Cas9 to verify the function of specific volatiles. Effects of exposure to tomato-specific volatiles on expression of S. litura detoxification enzyme genes will be determined by transcriptome sequencing, etc. The role of selected important detoxification genes in HIPVs-induced counter-defense in S. litura will be verified by RNA interference. This study will clarify the new counter-defense strategy in response to host plants HIPVs in the herbivorous insect, which has important implications for enriching plant defense versus insect counter-defense and co-evolutionary theory, and provides guidance for the application of plant volatiles in pest bio-control.

植物与昆虫神奇的互作与协同进化一直是科学家们感兴趣的科学问题。植物遭受植食性昆虫为害时可诱导产生抗虫物质和释放虫害诱导挥发物(HIPVs)对昆虫产生防御，昆虫也借助抗虫物质诱导解毒酶等对植物产生反防御。然而，植食性昆虫能否借助植物HIPVs形成反防御尚缺乏研究。本项目在证实番茄HIPVs能诱导重要鳞翅目害虫斜纹夜蛾提高对番茄抗性的基础上，研究HIPVs对斜纹夜蛾抵御番茄防御化合物及生长、产卵、趋性的影响；利用气质联用技术结合生物测定鉴定诱导害虫抗性的番茄挥发物组分；利用CRISPR/Cas9构建番茄挥发物合成突变体验证特定挥发物的功能；通过转录组测序等明确番茄特定挥发物对斜纹夜蛾解毒酶系的影响；选择重要解毒基因通过RNA干扰验证其诱导抗性功能。研究成果将阐明植食性昆虫适应宿主植物HIPVs的新型反防御策略，对丰富植物防御-昆虫反防御与协同进化理论有重要意义，并为挥发物的田间生防应用提供指导

植物与昆虫神奇的互作与协同进化一直是科学家们感兴趣的科学问题。过去三十年，植食性昆虫取食引起的植物诱导防御已经有了大量的研究，而昆虫相对应的反防御研究较少。植物在遭受植食性昆虫为害时，会释放虫害诱导植物挥发物(Herbivore-induced plant volatiles，HIPVs)。HIPVs能够直接抑制昆虫生长或趋避昆虫，吸引害虫天敌间接减轻害虫为害，还可以诱导临近健康植物提高抗虫性。然而，害虫如何应对植物HIPVs以及害虫是否存在HIPVs介导的反防御对策一直缺乏研究。本项目以重要经济作物番茄及其广食性鳞翅目害虫斜纹夜蛾为研究对象，揭示植食性昆虫针对番茄虫害诱导挥发物的反防御策略。番茄遭受斜纹夜蛾取食为害会诱导番茄植株萜烯合成酶基因家族基因（TPS系列基因）的表达和增加萜烯类HIPVs（包括α-蒎烯，柠檬烯，罗勒烯，水芹烯，石竹烯和 α-律草烯等）的释放，而斜纹夜蛾闻到这些HIPVs可以显著提高其对番茄抗虫物质（番茄碱、蛋白酶抑制剂）的抗性，同时也提高了其对农药毒死蜱和灭多威的抗药性；转录组数据和qRT-PCR显示，斜纹夜蛾闻到HIPVs后大量的解毒酶基因（10个P450基因、6个GST基因和30个酯酶基因）和8个编码昆虫表皮的角质层蛋白基因被诱导；挥发性萜烯α-蒎烯、罗勒烯、α-律草烯能够诱导斜纹夜蛾对次生物质的抗性，罗勒烯能够诱导斜纹夜蛾对农药的抗性；番茄茉莉酸合成突变体spr8的虫害诱导挥发物对斜纹夜蛾解毒能力没有显著影响，说明番茄HIPVs受茉莉酸信号途径调控。我们的研究揭示了植食性昆虫全新的反防御机制，即植食性昆虫幼虫的嗅觉能够感知植物产生的虫害诱导挥发物，进而诱导昆虫解毒系统，从而增强植食性昆虫抵御宿主植物化学防御以及外源毒素（包括杀虫剂）的能力。研究成果为调控植物HIPVs与昆虫解毒系统控制农业害虫奠定了理论基础。