Cytokinins Mediate Resistance against Pseudomonas syringae in Tobacco through Increased Antimicrobial Phytoalexin Synthesis Independent of Salicylic Acid Signaling
Cytokinins Mediate Resistance against Pseudomonas syringae in Tobacco through Increased Antimicrobial Phytoalexin Synthesis Independent of Salicylic Acid Signaling
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DOI：
10.1104/pp.111.182931
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发表时间：
2011-10-01
期刊：
影响因子：
7.4
通讯作者：
Roitsch, Thomas
中科院分区：
文献类型：
--
作者：
Grosskinsky, Dominik K.;Naseem, Muhammad;Roitsch, Thomas
细胞分裂素是参与整个植物发育的各种调节过程的植物激素，但它们也由病原体产生，并且已知调节植物免疫。一种新的转基因方法，使自动调节细胞分裂素的合成响应病原体感染表明，细胞分裂素介导增强的抵抗力，对有毒的半活体病原体假单胞菌烟粉虱。这被证实了两个额外的独立的转基因方法，以增加内源性细胞分裂素的生产和外源性供应的腺嘌呤和苯基脲衍生的细胞分裂素。细胞分裂素介导的抗性与烟草（Nicotiana tabacum）中两种主要抗菌植物抗毒素东莨菪内酯和辣椒二醇的杀菌活性和上调合成水平密切相关。这些植物防御素在潜在机制中的关键作用在功能上通过东莨菪内酯和辣椒二醇在植物中取代细胞分裂素信号的发现得到了证明：植物防御素预处理增加了对P. eriningae的抗性。与拟南芥中基于水杨酸依赖性转录控制的细胞分裂素防御机制相反，烟草中细胞分裂素介导的抗性基本上不依赖于水杨酸，并且在病原体特异性上不同。它也是独立的茉莉酸水平，活性氧和高糖抗性。细胞分裂素在茄科植物的初级防御反应中的新功能是通过在侵染的早期阶段高的植物抗毒素-病原体比率来介导的，其有效地限制病原体生长。讨论了这一机制对宿主植物和产生细胞分裂素的病原体的协同进化以及在农业上的实际应用的影响。
Cytokinins are phytohormones that are involved in various regulatory processes throughout plant development, but they are also produced by pathogens and known to modulate plant immunity. A novel transgenic approach enabling autoregulated cytokinin synthesis in response to pathogen infection showed that cytokinins mediate enhanced resistance against the virulent hemibiotrophic pathogen Pseudomonas syringae pv tabaci. This was confirmed by two additional independent transgenic approaches to increase endogenous cytokinin production and by exogenous supply of adenine-and phenylurea-derived cytokinins. The cytokinin-mediated resistance strongly correlated with an increased level of bactericidal activities and up-regulated synthesis of the two major antimicrobial phytoalexins in tobacco (Nicotiana tabacum), scopoletin and capsidiol. The key role of these phytoalexins in the underlying mechanism was functionally proven by the finding that scopoletin and capsidiol substitute in planta for the cytokinin signal: phytoalexin pretreatment increased resistance against P. syringae. In contrast to a cytokinin defense mechanism in Arabidopsis (Arabidopsis thaliana) based on salicylic acid-dependent transcriptional control, the cytokinin-mediated resistance in tobacco is essentially independent from salicylic acid and differs in pathogen specificity. It is also independent of jasmonate levels, reactive oxygen species, and high sugar resistance. The novel function of cytokinins in the primary defense response of solanaceous plant species is rather mediated through a high phytoalexin-pathogen ratio in the early phase of infection, which efficiently restricts pathogen growth. The implications of this mechanism for the coevolution of host plants and cytokinin-producing pathogens and the practical application in agriculture are discussed.