虫害诱导的植物挥发物代谢调控机制研究进展

Advances in metabolic regulation mechanism of herbivore-induced plant volatiles

长期受自然界的非生物/生物侵害,植物逐步形成了复杂的防御机制,为防御植食性昆虫的为害,植物释放虫害诱导产生的挥发性化合物(herbivore-induced plant volatiles,HIPVs)。HIPVs是植物-植食性昆虫-天敌三级营养关系之间协同进化的结果。HIPVs的化学组分因植物、植食性昆虫种类的不同而有差异。生态系统中,HIPVs可在植物与节肢动物、植物与微生物、虫害植物与邻近的健康植物、或同一植株的受害和未受害部位间起作用,介导防御性反应。HIPVs作为寄主定位信号,在吸引捕食性、寄生性天敌过程中起着重要作用。HIPVs还可以作为植物间信息交流的工具,启动植株的防御反应而增强抗虫性。不论从生态学还是经济学角度来看,HIPVs对于农林生态系中害虫综合治理策略的完善具有重要意义。前期的研究在虫害诱导植物防御的化学生态学方面奠定了良好基础,目前更多的研究转向阐述虫害诱导植物抗性的分子机制。为了深入了解HIPVs的代谢调控机制,主要从以下几个方面进行了综述。因为植食性昆虫取食造成的植物损伤是与昆虫口腔分泌物共同作用的结果,所以首先阐述口腔分泌物在防御反应中的作用。挥发物诱导素volicitin和β-葡萄糖苷酶作为口腔分泌物的组分,是产生HIPVs的激发子,通过调节伤信号诱发HIPVs的释放。接着阐述了信号转导途径对HIPVs释放的调节作用,并讨论了不同信号途径之间的交互作用。就HIPVs的代谢过程而言,其过程受信号转导途径(包括茉莉酸、水杨酸、乙烯、过氧化氢信号途径)的调控,其中茉莉酸信号途径是诱发HIPVs释放的重要途径。基于前人的研究,综述了HIPVs的主要代谢过程及其过程中关键酶类的调控作用。文中的HIPVs主要包括萜烯类化合物、绿叶挥发物和莽草酸途径产生的芳香族化合物,如水杨酸甲酯和吲哚等。作为化学信号分子,这些化合物中的一部分还能激活邻近植物防御基因的表达。萜烯合酶是各种萜烯类化合物合成的关键酶类,脂氧合酶、过氧化氢裂解酶也是绿叶挥发物代谢途径中的研究热点,而苯丙氨酸裂解酶和水杨酸羧基甲基转移酶分别是合成水杨酸及其衍生物水杨酸甲酯的关键酶类。这些酶类的基因在转录水平上调控着HIPVs代谢途径。最后展望了HIPVs的研究前景。

During the long term of interaction between plants and the abiotic stresses,and the biotic infestation,plants have evolved complex defensive mechanisms,for instance,plants emit herbivore-induced plant volatiles（HIPVs） so as to defend themselves against herbivores.HIPVs are the results of co-evolution in tritrophic interactions among plants,herbivores and natural enemies.The chemical compositions of the volatile compounds vary with both plant and herbivorous insect species.Within the various ecosystems,HIPVs play an important role in mediating interactions between plants and arthropods,plants and microorganisms,herbivore-damaging plants and undamaged neighboring plants,as well as damaged parts and undamaged parts of the same plant,and they mediate plants defensive responses.As host location signals,HIPVs play a critical role in attracting predatory and parasitical natural enemies.HIPVs may also act as chemical communication signals among plants,and trigger defensive responses against herbivores.From an ecological or economical point of view,the research and application of HIPVs are of great importance for development of integrated pest management strategy.Previous researches significantly enriched our understanding of insect chemical ecology related to herbivore-induced plant defense.However,a great deal of attention has recently been directed towards elucidating the molecular nature of induced plant resistance.In this review,we address following key issues related to the metabolic regulation mechanisms of HIPVs.First,we discuss the functionality of oral secretions of herbivores in the defense of plants,since plant damages are resulted from both herbivore mouthpart chawing（or piercing） and oral secretions.The synomone inducers Volicitin and β-glucosidase are components of oral secretions,and trigger the release of HIPVs,at least in part,by modulating the wound signals.Subsequently,we address the signal transduction pathways and their regulatory roles in the releases of HIPVs,and discussthe interaction among various signaling pathways.As for metabolic process of HIPVs,it is regulated by signaling pathways,including jasmonic acid（JA）,salicylic acid（SA）,ethylene and H2O2.Among which,JA has long been suggested to be an important regulator of HIPVs.Based on the previous studies,we summarize the key metabolic processes of HIPVs and the regulation roles of key enzymes in the main transduction paths.HIPVs discussed in the current paper include terpenes,green leaf volatiles and aromatic compounds derived from shikimic acid pathway such as methyl salicylate（MeSA） and indole.As chemical signaling molecules,some compounds can also activate the expression of defense genes in neighboring plants.Terpene synthases are key enzymes involved in terpenoids production.Lipoxygenase and hydroperoxide lyase are the focuses in recent researches on the metabolic pathway of green leaf volatiles.Phenylalanine ammonia lyase and salicylic acid carboxyl methyltransferase are key enzymes involved in the formation of SA and its derivative MeSA,respectively.Whereas,the genes of these enzymes regulate the metabolic pathways of HIPVs at transcription level.Finally,we give a brief outlook of the future research and application of HIPVs.