Two-component elements mediate interactions between cytokinin and salicylic acid in plant immunity.
Two-component elements mediate interactions between cytokinin and salicylic acid in plant immunity.
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DOI：
10.1371/journal.pgen.1002448
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发表时间：
2012-01
期刊：
影响因子：
4.5
通讯作者：
Kieber JJ
中科院分区：
文献类型：
--
作者：
Argueso CT;Ferreira FJ;Epple P;To JP;Hutchison CE;Schaller GE;Dangl JL;Kieber JJ
最近的研究表明，激素在植物免疫中起着重要作用。我们现在开始了解不同激素信号网络之间的串扰对植物-病原体相互作用结果的贡献。细胞分裂素是调节发育和对环境的反应的植物激素。细胞分裂素信号传导涉及类似于细菌和真菌用于感知和反应各种环境刺激的双组分系统的磷酸化回路。在这项研究中，我们问是否细胞分裂素和细胞分裂素信号成分有助于植物免疫。我们表明，细胞分裂素水平在拟南芥中是重要的，在确定免疫反应的幅度，最终影响植物-病原体相互作用的结果。我们发现，高浓度的细胞分裂素导致增加的防御反应的毒性卵菌病原体，通过一个过程，这是依赖于水杨酸（SA）的积累和激活的防御基因的表达。令人惊讶的是，用较低浓度的细胞分裂素治疗导致易感性增加。细胞分裂素在植物免疫中的这些功能需要宿主磷酸化系统，并且部分由A型反应调节剂介导，所述A型反应调节剂充当基础和病原体诱导的SA依赖性基因表达的负调节剂。我们的研究结果支持一个模型，其中细胞分裂素上调植物免疫通过海拔SA依赖的防御反应，SA反过来反馈抑制细胞分裂素信号。细胞分裂素和SA信号网络之间的串扰可能有助于植物微调对病原体的防御反应。植物激素在植物生命周期的许多方面发挥着重要作用，从发育的调节到对不断变化的环境条件的反应。在过去的十年中，激素在植物对各种病原体的免疫中的重要性已经被发现。在这份手稿中，我们证明，在模式植物拟南芥的植物激素细胞分裂素的信号系统组件也介导植物免疫。我们证明，这涉及到A类拟南芥反应调节剂的过程中发生的植物防御激素水杨酸的下游，并涉及到主机的两个组件phosphorelay。此外，我们表明，细胞分裂素的水平是重要的，在确定植物免疫的幅度，最终影响植物-病原体相互作用的结果。最后，我们的研究结果表明，水杨酸负调控细胞分裂素信号，这可能有助于微调细胞分裂素在植物免疫中的作用。鉴于防御反应的高能量成本和细胞分裂素在碳分配和能量分配中的作用，我们假设这里揭示的机制可能有助于调节可以分配到防御反应中的能量水平，这是植物生物学的一个重要方面。
Recent studies have revealed an important role for hormones in plant immunity. We are now beginning to understand the contribution of crosstalk among different hormone signaling networks to the outcome of plant–pathogen interactions. Cytokinins are plant hormones that regulate development and responses to the environment. Cytokinin signaling involves a phosphorelay circuitry similar to two-component systems used by bacteria and fungi to perceive and react to various environmental stimuli. In this study, we asked whether cytokinin and components of cytokinin signaling contribute to plant immunity. We demonstrate that cytokinin levels in Arabidopsis are important in determining the amplitude of immune responses, ultimately influencing the outcome of plant–pathogen interactions. We show that high concentrations of cytokinin lead to increased defense responses to a virulent oomycete pathogen, through a process that is dependent on salicylic acid (SA) accumulation and activation of defense gene expression. Surprisingly, treatment with lower concentrations of cytokinin results in increased susceptibility. These functions for cytokinin in plant immunity require a host phosphorelay system and are mediated in part by type-A response regulators, which act as negative regulators of basal and pathogen-induced SA–dependent gene expression. Our results support a model in which cytokinin up-regulates plant immunity via an elevation of SA–dependent defense responses and in which SA in turn feedback-inhibits cytokinin signaling. The crosstalk between cytokinin and SA signaling networks may help plants fine-tune defense responses against pathogens. Plant hormones play an important role in many aspects of a plant's life cycle, from the regulation of development to responses to constantly changing environmental conditions. In the past decade, the importance of hormones in plant immunity against a variety of pathogens has been uncovered. In this manuscript, we demonstrate that in the model plant species Arabidopsis thaliana components of the signaling system of the plant hormone cytokinin also mediate plant immunity. We demonstrate that this involves the type-A class of Arabidopsis response regulators in a process that occurs downstream of the plant defense hormone salicylic acid and involves a host two-component phosphorelay. Moreover, we show that the levels of cytokinin are important in determining the amplitude of plant immunity, ultimately influencing the outcome of plant–pathogen interactions. Finally, our results indicate that salicylic acid negatively regulates cytokinin signaling, which may serve to fine-tune the effects of cytokinin in plant immunity. Given the high energy costs of defense responses and the role of cytokinins in carbon partitioning and energy allocation, we hypothesize that the mechanisms uncovered here may help regulate the levels of energy that can be allocated into defense responses, an important aspect in the biology of plants.
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