植物防御的新发现:植物-植物相互交流

New discovery about plant defense: plant-plant communication

植物和昆虫在长期的相互作用过程中形成了复杂的防御体系。近年来,人们发现植物在受到外界伤害后,它们邻近的健康植物能够感受到威胁来临,并积极表达抗性基因和产生防御物质。这种现象被称为"植物-植物相互交流"。一系列的相关研究表明:绿叶挥发物和萜烯类物质是受伤害植物对邻近健康植物发送的主要信号,邻近的健康植物在接收到这些挥发性有机化合物信号后,直接防御和间接防御能力都能够迅速提升。人们猜测植物挥发性有机化合物"启动"了邻近健康植物的多种防御反应,使它们在面临真正威胁时迅速做出防御反应。然而,植物-植物交流的分子机制至今尚不清楚。我们运用拟南芥(Arabidopsis thaliana)全基因组芯片技术和突变体材料,对植物-植物交流的分子机理进行了探讨。结果发现:有效的挥发性有机化合物并不限于绿叶挥发物和萜烯类物质,且挥发性有机化合物的种类和节律能够相互配合,从而达到最佳效果;邻近健康植物的乙烯信号途径在植物-植物交流过程中是不可或缺的,茉莉酸信号起到了辅助和信号放大的作用。

Plants have developed sophisticated defense systems during their long-time interaction with insects. About three decades ago, it was found that insect-damaged plants can prime their neighbors to express defense proteins, and this phenomenon was called ＂plant-plant communication＂. A series of studies have focused on this topic since then. Results indicate that green-leaf volatiles and terpenes are the main chemicals emitted from the infested plant to the healthy neighbor plants, while direct and indirect defenses of the neighbors may both be regulated. An im- portant consensus about plant-plant communication mechanisms until now is that the volatile organic chemicals do not induce resistance directly, but sensitize the receiver plant for augmented response to subsequent damages, which is called ＂priming＂. However, the molecular mechanism of this phenomenon is unclear. We used Arabidop- sis thaliana genome arrays and mutants to examine the molecular mechanisms of plant-plant communication. Our results indicate that several volatiles are effective signals, and the active volatiles are correlated with their emis- sion rhythms to achieve the optimum effect. The ethylene pathway is indispensable for sensing the induction sig- nal in the early phase of induction, while Jasmonic acid signal can amplify the effects. As the mechanisms of plant-plant communication become clearer, future research may focus on the origin and evolution of this phe- nomenon.