MAPKs信号途径介导的烟草与烟蚜互作对CO2浓度升高的响应机制

Previous studies found elevated CO2 could affect the population dynamic of aphids by altering the resistance of host plant, however, the mechanism is unknown. The field open-top chambers are used to control the doubled-ambient carbon dioxide (CO2) concentration for the treatment factor, the plant Nicotiana attenuata and tobacco aphid Myzus persicae as the research object, plant mitogen-activated protein kinases (MAPKs) signaling pathway as the starting point, defensive phytohormones, and stably transformed N. attenuata plants silenced in WIPK(irWIPK), SIPK(irSIPK), MPK4(irMPK4), AOC(irAOC), SA synthesis (NahG) and wild-type WT are comparatively examined in this project. From the defensive phytohormones, aphid-induced defense pathways, the tobacco aphid feeding behavior, population fitness and molecular regulation point of view, we comprehensively examine the function of MAPKs signaling pathway in the interaction between tobacco and aphid when response to elevated CO2. This project compares the response characteristics of irWIPK, irSIPK, irMPK4, irAOC, NahG plants with wild-type plants under elevated CO2, to prove the effect of MAPKs signaling pathway and elevated CO2 on the synthesis of defensive phytohormones (Jasmonic acid and salicylic acid) in host plant when infested by aphid. Pea aphid infestation characteristics and population parameters on irWIPK, irSIPK, irMPK4 and wild-type tobacco were determined, in order to clarify the role of MAPKs signaling pathway in plant response to aphid infestation, and eventually to reveal the response mechanisms of interaction between plant and herbivorous insect to elevated CO2. The outcomes of this project are able to predict the future development trends of the interactions between plants and aphids in the context of elevated CO2 concentration, in order to provide a scientific basis on giving a full play to the way to the main source of resistance against the crop pests in ecological pest control.

前期研究表明，CO2浓度升高可通过改变寄主植物诱导抗性影响蚜虫种群动态，但其调控的分子机制并不清楚。本项目拟利用野外开顶式二氧化碳（CO2）浓度控制箱，以CO2浓度升高为处理因子，以烟草和烟蚜为研究对象，基于植物受到烟蚜为害后最先诱导的丝裂原活化蛋白激酶（MAPKs）信号通路入手，以转基因植物（irSIPK，irWIPK，irSIPK，irAOC，NahG）与野生型烟草为研究材料，通过分析下游植物抗性激素的合成与代谢、植物抗性基因的表达以及蚜虫种群适合度，系统研究MAPKs信号途径在烟蚜介导的烟草免疫防卫系统中的作用及其对CO2浓度升高的响应机制。通过比较RNAi转基因材料对蚜虫及CO2浓度升高的响应特征，了解烟蚜对不同RNAi转基因植物与野生型烟草的为害特征、取食行为及种群参数的变化规律，从而明确MAPKs信号途径在植物响应蚜虫为害过程中的作用，预测植物与蚜虫互作关系在未来CO2浓度升高

本项目利用野外开顶式二氧化碳（CO2）浓度控制箱，以CO2浓度升高为处理因子，以烟草和烟蚜为研究对象，以RNAi转基因植物（irSIPK，irWIPK，irSIPK）与野生型烟草为研究材料，从植物对烟蚜唾液蛋白的识别、早期诱导的丝裂原活化蛋白激酶（MAPKs）信号通路、下游植物抗性激素的合成与代谢、植物抗性基因的表达以及蚜虫种群适合度和分子调控等方面，系统研究MAPKs途径在烟草介导蚜虫为害的免疫防卫系统中的作用及其对CO2浓度升高的响应机制，圆满完成了各项计划任务，并取得了以下结论。（1）揭示大气CO2浓度升高对植物抗蚜信号上游的调控机制：发现CO2升高会增加植物丝裂原活化蛋白激酶MPK4的表达，一方面抑制下游茉莉酸信号途径的表达，降低植物对蚜虫取食的抗性；另一方面诱导气孔闭合增加植物水势，有利于提高蚜虫的取食效率，此研究揭示了植物MPK4是病原相关分子模式诱导（PTI）的昆虫抗性响应大气CO2浓度升高的重要元件，从而进一步影响蚜虫的种群发生。（2）明确CO2浓度升高条件下植物MAPK信号途径改变的原因：大气CO2浓度升高条件下植物的光合底物增加，促进光合作用，与此同时，过多的光合产物会诱导植物产生活性氧簇（ROS），植物通过增加MPK4来降低植物过多的ROS对自身产生的不利影响。（3）植物ROS的积累会通过改变蚜虫取食行为促进蚜虫传播植物病毒：当黄瓜花叶病毒侵染植物后，其病毒沉默抑制子2b蛋白可以诱导植物产生ROS，植物的ROS的产生导致媒介蚜虫刺探频率增加，从而导致蚜虫获毒量增加，进而增加蚜虫的传毒能力。本项目全面系统揭示烟草－烟蚜对CO2浓度升高的响应机制。项目实施3年来在国内外重要刊物上发表8篇论文，SCI论文5篇。为以充分发挥作物内源抗性途径为主的害虫生态调控提供科学依据。