Department of Plant Pathology, University of Kentucky, Lexington, KY 40546, USA.
Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY 40546, USA.
Sci Adv. 2018 May 30;4(5):eaar4509. doi: 10.1126/sciadv.aar4509. eCollection 2018 May.
Pipecolic acid (Pip), a non-proteinaceous product of lysine catabolism, is an important regulator of immunity in plants and humans alike. In plants, Pip accumulates upon pathogen infection and has been associated with systemic acquired resistance (SAR). However, the molecular mechanisms underlying Pip-mediated signaling and its relationship to other known SAR inducers remain unknown. We show that in plants, Pip confers SAR by increasing levels of the free radicals, nitric oxide (NO), and reactive oxygen species (ROS), which act upstream of glycerol-3-phosphate (G3P). Plants defective in NO, ROS, G3P, or salicylic acid (SA) biosynthesis accumulate reduced Pip in their distal uninfected tissues although they contain wild-type-like levels of Pip in their infected leaves. These data indicate that de novo synthesis of Pip in distal tissues is dependent on both SA and G3P and that distal levels of SA and G3P play an important role in SAR. These results also suggest a unique scenario whereby metabolites in a signaling cascade can stimulate each other's biosynthesis depending on their relative levels and their site of action.
哌可酸（Pip）是赖氨酸分解的非蛋白产物，是植物和人类免疫的重要调节剂。在植物中，Pip 在病原体感染时积累，并与系统获得性抗性（SAR）有关。然而，Pip 介导的信号转导的分子机制及其与其他已知 SAR 诱导剂的关系仍不清楚。我们表明，在植物中，Pip 通过增加自由基、一氧化氮（NO）和活性氧物种（ROS）的水平来赋予 SAR，而这些自由基、一氧化氮（NO）和活性氧物种（ROS）作用于甘油-3-磷酸（G3P）的上游。尽管其感染叶片中含有类似野生型的 Pip 水平，但在 NO、ROS、G3P 或水杨酸（SA）生物合成缺陷的植物中，其远端未感染组织中积累的 Pip 减少。这些数据表明，远端组织中 Pip 的从头合成既依赖于 SA 又依赖于 G3P，并且远端的 SA 和 G3P 水平在 SAR 中起着重要作用。这些结果还表明了一种独特的情况，即在信号级联中的代谢物可以根据其相对水平及其作用部位相互刺激彼此的生物合成。
