Systemic response to avirulent bacterial infection. Arabidopsis thaliana

In the absence of adaptive immunity displayed by animals, plants respond locally to biotic challenge via inducible basal defense networks activated through recognition and response toconserved pathogen associated molecular patterns (PAMPs). In addition, immunity can be induced in tissues remote from infection sites via systemic acquired resistance (SAR), initiated following gene-for-gene recognition between plant resistance proteins and microbial effectors.The nature of the mobile signal and remotely activated networks responsible for establishing SAR remain unclear. Here we show that despite the absence of PAMP contact, systemically responding leaves rapidly activate a SAR transcriptional signature with strong similarity to local basal defense. Jasmonates have previously been implicated in systemic signalling in response to wounding and plant herbivory but not SAR. We present several lines of evidence that suggest jasmonates may also be central to SAR. Jasmonic acid (JA) rapidly accumulates in phloem exudates of leaves challenged with an avirulent strain of Pseudomonas syringae. In systemically responding leaves transcripts associated with jasmonate biosynthesis are upregulated and JA increases transiently. SAR can be mimicked by foliar JA application and is abrogated in mutants impaired in jasmonate synthesis or response. We conclude that, jasmonate signalling appears to mediate long-distance information transmission. Moreover, the systemic transcriptional response shares extraordinary overlap with local herbivory and wounding responses, indicating that jasmonates may be central to an evolutionarily conserved signalling network, which decodes multiple abiotic and biotic stress signals. Experimenter name: William Truman Experimenter phone: [phone] Experimenter fax: [phone] Experimenter address: School of Biosciences Experimenter address: Geoffrey Pope Building Experimenter address: Stocker Road Experimenter address: Exeter Experimenter address: Devon Experimenter zip/postal_code: EX4 4QD Experimenter country: UK Keywords: infection Overall design: 9 samples were used in this experiment

相较于动物所具备的适应性免疫，植物可通过识别并响应保守的病原相关分子模式（PAMPs）所激活的诱导型基础防御网络，对生物胁迫产生局部应答。此外，在植物抗病蛋白与微生物效应蛋白发生基因对基因识别后，可通过系统获得性抗性（SAR）在远离侵染位点的组织中诱导免疫应答。目前，介导系统获得性抗性建立的移动信号与远端激活的调控网络的本质仍不明确。本研究发现，即使未接触病原相关分子模式，系统应答的叶片仍可快速激活与局部基础防御高度相似的系统获得性抗性转录特征。此前，茉莉酸类物质（jasmonates）已被证实参与植物应对机械损伤与植食性昆虫取食的系统性信号通路，但尚未发现其与系统获得性抗性相关。本研究通过多组实验证据表明，茉莉酸类物质同样可能是系统获得性抗性的核心调控因子。茉莉酸（JA）可在受无毒丁香假单胞菌（Pseudomonas syringae）菌株侵染的叶片韧皮部渗出液中快速积累。在系统应答的叶片中，与茉莉酸生物合成相关的转录本表达量上调，且茉莉酸水平会出现一过性升高。通过叶面施加茉莉酸即可模拟系统获得性抗性，而茉莉酸合成或信号应答受损的突变体则无法触发系统获得性抗性。综上，茉莉酸信号通路似乎介导了植物的长距离信息传递。此外，系统应答的转录特征与植物局部的植食性取食及机械损伤应答存在极高的重叠度，这表明茉莉酸类物质可能是一类进化保守的信号网络的核心组分，该网络可解码多种生物与非生物胁迫信号。实验人员姓名：威廉·特鲁曼（William Truman）；实验人员电话：[phone]；实验人员传真：[phone]；实验人员通讯地址：英国德文郡埃克塞特市斯托克路杰弗里·波普大楼生命科学学院；邮政编码：EX4 4QD；关键词：侵染；实验设计：本实验共使用9个样本。