Lim Chae Woo, Lee Sung Chul
Department of Life Science, Chung-Ang University, Seoul, 156-756, Korea.
Plant Mol Biol. 2015 Jun;88(3):313-24. doi: 10.1007/s11103-015-0330-1. Epub 2015 May 13.
Stomata are natural pores of plants and constitute the entry points for water during transpiration. However, they also facilitate the ingress of potentially harmful bacterial pathogens. The phytohormone abscisic acid (ABA) plays a pivotal role in protecting plants against biotic stress, by regulating stomatal closure. In the present study, we investigated the mechanism whereby ABA influences plant defense responses to Pseudomonas syringae pv. tomato (Pst) DC3000, which is a virulent bacterial pathogen of Arabidopsis, at the pre-invasive stage. We found that overexpression of two ABA receptors, namely, RCAR4/PYL10-OX and RCAR5/PYL11-OX (hereafter referred to as RCARs), resulted in ABA-hypersensitive phenotypes being exhibited during the seed germination and seedling growth stages. Sensitivity to ABA enhanced the resistance of RCAR4-OX and RCAR5-OX plants to Pst DC3000, through promoting stomatal closure leading to the development of resistance to this bacterial pathogen. Protein phosphatase HAB1 is an important component that is responsible for ABA signaling and which interacts with ABA receptors. We found that hab1 mutants exhibited enhanced resistance to Pst DC3000; moreover, similar to RCAR4-OX and RCAR5-OX plants, this enhanced resistance was correlated with stomatal closure. Taken together, our findings demonstrate that alteration of RCAR4- or RCAR5-HAB1 mediated ABA signaling influences resistance to bacterial pathogens via stomatal regulation.
气孔是植物的天然孔隙，是蒸腾作用期间水分进入的入口。然而，它们也为潜在有害的细菌病原体的侵入提供了便利。植物激素脱落酸（ABA）通过调节气孔关闭，在保护植物免受生物胁迫方面发挥着关键作用。在本研究中，我们调查了ABA在侵入前阶段影响植物对丁香假单胞菌番茄致病变种（Pst）DC3000（拟南芥的一种致病细菌病原体）防御反应的机制。我们发现，两种ABA受体即RCAR4/PYL10-OX和RCAR5/PYL11-OX（以下简称RCARs）的过表达导致在种子萌发和幼苗生长阶段表现出ABA超敏表型。对ABA的敏感性通过促进气孔关闭增强了RCAR4-OX和RCAR5-OX植物对Pst DC3000的抗性，从而产生对这种细菌病原体的抗性。蛋白磷酸酶HAB1是负责ABA信号传导并与ABA受体相互作用的重要组分。我们发现hab1突变体对Pst DC3000表现出增强的抗性；此外，与RCAR4-OX和RCAR5-OX植物类似，这种增强的抗性与气孔关闭相关。综上所述，我们的研究结果表明，RCAR4-或RCAR5-HAB1介导的ABA信号改变通过气孔调节影响对细菌病原体的抗性。
