Polyamines (PAs) are small aliphatic amines with important regulatory activities in plants. Biotic stress results in changes in PA levels due to de novo synthesis and PA oxidation. In Arabidopsis thaliana five FAD-dependent polyamine oxidase enzymes (AtPAO1-5) participate in PA back-conversion and degradation. PAO activity generates H2O2, an important molecule involved in cell signaling, elongation, programmed cell death, and defense responses. In this work we analyzed the role of AtPAO genes in the Arabidopsis thaliana-Pseudomonas syringae pathosystem. AtPAO1 and AtPAO2 genes were transcriptionally up-regulated in infected plants. Atpao1-1 and Atpao2-1 single mutant lines displayed altered responses to Pseudomonas, and an increased susceptibility was found in the double mutant Atpao1-1 x Atpao2-1. These polyamine oxidases mutant lines showed disturbed contents of ROS (H2O2 and O2-) and altered activities of RBOH, CAT and SOD enzymes both in infected and control plants. In addition, changes in the expression levels of AtRBOHD, AtRBOHF, AtPRX33, and AtPRX34 genes were also noticed. Our data indicate an important role for polyamine oxidases in plant defense and ROS homeostasis.

中文翻译：

---

拟南芥 PAO 活性的降低导致 RBOH 活性增加、ROS 含量增加和对假单胞菌的反应改变

多胺 (PA) 是小的脂肪胺，在植物中具有重要的调节活性。由于从头合成和 PA 氧化，生物应激导致 PA 水平发生变化。在拟南芥中，五种依赖 FAD 的多胺氧化酶 (AtPAO1-5) 参与 PA 的反向转换和降解。PAO 活性产生 H2O2，H2O2 是一种重要的分子，参与细胞信号传导、伸长、程序性细胞死亡和防御反应。在这项工作中，我们分析了 AtPAO 基因在拟南芥-丁香假单胞菌病理系统中的作用。AtPAO1 和 AtPAO2 基因在受感染植物中转录上调。Atpao1-1 和 Atpao2-1 单突变株系对假单胞菌的反应发生改变，双突变株 Atpao1-1 x Atpao2-1 的易感性增加。这些多胺氧化酶突变株系在感染植物和对照植物中表现出 ROS（H2O2 和 O2-）含量紊乱以及 RBOH、CAT 和 SOD 酶活性改变。此外，还注意到 AtRBOHD、AtRBOHF、AtPRX33 和 AtPRX34 基因表达水平的变化。我们的数据表明多胺氧化酶在植物防御和 ROS 稳态中的重要作用。