Laboratoire de Stress, Défenses, et Reproduction des Plantes, L'Unité de Recherche Vignes et Vins de Champagne, Equipe d'Accueil 4707, Université de Reims Champagne-Ardenne, F-51687 Reims Cedex 2, France.
Plant Physiol. 2012 Nov;160(3):1630-41. doi: 10.1104/pp.112.201913. Epub 2012 Sep 11.
Plant resistance to phytopathogenic microorganisms mainly relies on the activation of an innate immune response usually launched after recognition by the plant cells of microbe-associated molecular patterns. The plant hormones, salicylic acid (SA), jasmonic acid, and ethylene have emerged as key players in the signaling networks involved in plant immunity. Rhamnolipids (RLs) are glycolipids produced by bacteria and are involved in surface motility and biofilm development. Here we report that RLs trigger an immune response in Arabidopsis (Arabidopsis thaliana) characterized by signaling molecules accumulation and defense gene activation. This immune response participates to resistance against the hemibiotrophic bacterium Pseudomonas syringae pv tomato, the biotrophic oomycete Hyaloperonospora arabidopsidis, and the necrotrophic fungus Botrytis cinerea. We show that RL-mediated resistance involves different signaling pathways that depend on the type of pathogen. Ethylene is involved in RL-induced resistance to H. arabidopsidis and to P. syringae pv tomato whereas jasmonic acid is essential for the resistance to B. cinerea. SA participates to the restriction of all pathogens. We also show evidence that SA-dependent plant defenses are potentiated by RLs following challenge by B. cinerea or P. syringae pv tomato. These results highlight a central role for SA in RL-mediated resistance. In addition to the activation of plant defense responses, antimicrobial properties of RLs are thought to participate in the protection against the fungus and the oomycete. Our data highlight the intricate mechanisms involved in plant protection triggered by a new type of molecule that can be perceived by plant cells and that can also act directly onto pathogens.
植物对植物病原微生物的抗性主要依赖于先天免疫反应的激活，通常在植物细胞识别微生物相关分子模式后发生。植物激素水杨酸（SA）、茉莉酸和乙烯已成为参与植物免疫信号网络的关键因子。鼠李糖脂（RLs）是细菌产生的糖脂，参与表面运动和生物膜的形成。在这里，我们报告 RLs 在拟南芥中引发免疫反应，其特征是信号分子的积累和防御基因的激活。这种免疫反应参与了对半活体细菌丁香假单胞菌 pv 番茄、活体卵菌拟南芥疫霉和坏死真菌 Botrytis cinerea 的抗性。我们表明，RL 介导的抗性涉及不同的信号通路，这些通路取决于病原体的类型。乙烯参与 RL 诱导的对 H. arabidopsidis 和 P. syringae pv 番茄的抗性，而茉莉酸对于对 B. cinerea 的抗性是必需的。SA 参与了所有病原体的限制。我们还提供了证据表明，SA 依赖性植物防御在受到 B. cinerea 或 P. syringae pv 番茄的挑战后，会被 RLs 增强。这些结果突出了 SA 在 RL 介导的抗性中的核心作用。除了激活植物防御反应外，RLs 的抗菌特性被认为参与了对真菌和卵菌的保护。我们的数据强调了由一种可以被植物细胞感知的新型分子触发的植物保护所涉及的复杂机制，并且这种分子还可以直接作用于病原体。
