The abscisic acid (ABA) signalling pathway is involved in the plant response to osmotic stress caused by drought and/or salinity. Although the ABA signalling pathway has been elucidated in Arabidopsis, it remains elusive in woody poplars. In this study, genome-wide analyses of U-box genes in poplars revealed that a U-box E3 ubiquitin ligase gene, PalPUB79, is significantly induced following drought, salinity and ABA signalling. PalPUB79 overexpression enhanced drought tolerance in transgenic poplars, while PalPUB79 RNAi lines were more sensitive to drought. PalPUB79 positively regulated ABA signalling pathway. Furthermore, PalPUB79 interacted with PalWRKY77, a negative transcriptional regulator of ABA signalling, and mediated its ubiquitination for degradation, therefore counteracting its inhibitory effect on PalRD26 transcription. However, the finding that PalWRKY77 negatively regulates PalPUB79 expression was indicative of a negative feedback loop between PalWRKY77 and PalPUB79 during ABA signalling in poplar. These findings provide novel insight into the mechanism through which PalPUB79 enhances the ABA-mediated stress response in woody poplars.

中文翻译：

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U-box E3 泛素连接酶 PalPUB79 通过泛素化杨树中的 PalWRKY77 正向调节 ABA 依赖性干旱耐受性


脱落酸 (ABA) 信号通路参与植物对干旱和/或盐度引起的渗透胁迫的反应。尽管 ABA 信号通路已在拟南芥中得到阐明，但在木本杨树中仍然难以捉摸。在这项研究中，对杨树中 U-box 基因的全基因组分析表明，U-box E3 泛素连接酶基因PalPUB79在干旱、盐度和 ABA 信号传导后显着被诱导。 PalPUB79过表达增强了转基因杨树的耐旱性，而PalPUB79 RNAi 品系对干旱更敏感。 PalPUB79正向调节 ABA 信号通路。此外，PalPUB79 与 ABA 信号传导的负转录调节因子 PalWRKY77 相互作用，并介导其泛素化降解，从而抵消其对PalRD26转录的抑制作用。然而，PalWRKY77 负向调节PalPUB79表达的发现表明杨树 ABA 信号传导过程中 PalWRKY77 和 PalPUB79 之间存在负反馈环。这些发现为PalPUB79增强木本杨树 ABA 介导的应激反应的机制提供了新的见解。