Polyamines are important for non‐climacteric fruit ripening according to an analysis of the model plant strawberry. However, the molecular mechanism underlying the polyamine accumulation during ripening has not been fully elucidated. In this study, an examination of our proteome data related to strawberry fruit ripening revealed a putative polyamine oxidase 5, FaPAO5, which was localized in the cytoplasm and nucleus. Additionally, FaPAO5 expression levels as well as the abundance of the encoded protein continually decreased during ripening. Inhibiting FaPAO5 expression by RNAi promoted Spd, Spm, and ABA accumulation while inhibited H₂O₂ production, which ultimately enhanced ripening as evidenced by the ripening‐related events and corresponding gene expression changes. The opposite effects were observed in FaPAO5‐overexpressing transgenic fruits. Analyses of the binding affinity and enzymatic activity of FaPAO5 with Spm, Spd, and Put uncovered a special role for FaPAO5 in the terminal catabolism of Spm and Spd, with a K_d of 0.21 and 0.29 µM, respectively. Moreover, FaPAO5 expression was inhibited by ABA and promoted by Spd and Spm. Furthermore, the RNA‐seq analysis of RNAi and control fruits via differentially expressed genes (DEGs) indicated the six most enriched pathways among the differentially expressed genes were related to sugar, abscisic acid, ethylene, auxin, gibberellin, and Ca²⁺. Among four putative PAO genes in the strawberry genome, only FaPAO5 was confirmed to influence fruit ripening. In conclusion, FaPAO5 is a negative regulator of strawberry fruit ripening and modulates Spm/Spd levels as a signaling event, in which ABA plays a central role.

中文翻译：

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FaPAO5 调节 Spm/Spd 水平作为草莓果实成熟过程中的信号。


根据对模型植物草莓的分析，多胺对于非更年期果实成熟很重要。然而，成熟过程中多胺积累的分子机制尚未完全阐明。在这项研究中，对与草莓果实成熟相关的蛋白质组数据的检查揭示了一种假定的多胺氧化酶 5，FaPAO5，它位于细胞质和细胞核中。此外， FaPAO5表达水平以及编码蛋白的丰度在成熟过程中持续下降。通过 RNAi 抑制FaPAO5表达促进 Spd、Spm 和 ABA 积累，同时抑制 H ₂ O ₂产生，最终促进成熟，如成熟相关事件和相应基因表达变化所证明的那样。在FaPAO5过度表达的转基因水果中观察到相反的效果。对 FaPAO5 与 Spm、Spd 和 Put 的结合亲和力和酶活性的分析发现，FaPAO5 在 Spm 和 Spd 的末端分解代谢中具有特殊作用， K _d分别为 0.21 和 0.29 µM。此外， FaPAO 5 的表达被ABA 抑制，并被Spd 和Spm 促进。此外，通过差异表达基因（DEG）对RNAi和对照水果进行的RNA-seq分析表明，差异表达基因中最富集的六个途径与糖、脱落酸、乙烯、生长素、赤霉素和Ca ²⁺相关。在草莓基因组中的四个假定的PAO基因中，只有FaPAO5被证实会影响果实成熟。 总之，FaPAO5 是草莓果实成熟的负调节因子，并作为信号事件调节 Spm/Spd 水平，其中 ABA 发挥核心作用。