He Fang, Niu Meng-Xue, Wang Ting, Li Jun-Lin, Shi Yu-Jie, Zhao Jiu-Jiu, Li Hao, Xiang Xiang, Yang Peng, Wei Shu-Ying, Lin Tian-Tian, Huang Xiong, Xia Xinli, Wan Xue-Qin
National Forestry and Grassland Administration Key Laboratory of Forest Resources Conservation and Ecological Safety on the Upper Reaches of the Yangtze River and Forestry Ecological Engineering in the Upper Reaches of the Yangtze River Key Laboratory of Sichuan Province, College of Forestry, Sichuan Agricultural University, Chengdu 611130, China.
College of Biological Sciences and Technology, Beijing Forestry University, Beijing 100083, China.
Plant Physiol. 2024 Dec 2;196(4):2936-2955. doi: 10.1093/plphys/kiae497.
Abscisic acid (ABA) signaling has been implicated in plant responses to water deficit-induced osmotic stress. However, the underlying molecular mechanism remains unelucidated. This study identified the RING-type E3 ubiquitin ligase RING ZINC FINGER PROTEIN1 (PtrRZFP1) in poplar (Populus trichocarpa), a woody model plant. PtrRZFP1 encodes an ubiquitin E3 ligase that participates in protein ubiquitination. PtrRZFP1 mainly functions in the nucleus and endoplasmic reticulum and is activated by drought and ABA. PtrRZFP1-overexpressing transgenic poplars (35S:PtrRZFP1) showed greater tolerance to drought, whereas PtrRZFP1-knockdown lines (KD-PtrRZFP1) showed greater sensitivity to drought. Under treatment with polyethylene glycol and ABA, PtrRZFP1 promoted the production of nitric oxide and hydrogen peroxide in stomatal guard cells, ultimately enhancing stomatal closure and improving drought tolerance. Additionally, PtrRZFP1 physically interacted with the clade A Protein Phosphatase 2C protein PtrPP2C-9, a core regulator of ABA signaling, and mediated its ubiquitination and eventual degradation through the ubiquitination-26S proteasome system, indicating that PtrRZFP1 positively regulates the ABA signaling pathway. Furthermore, the PtrPP2C-9-overexpression line was insensitive to ABA and more sensitive to drought than the wild-type plants, whereas the opposite phenotype was observed in 35S:PtrRZFP1 plants. In general, PtrRZFP1 negatively regulates the stability of PtrPP2C-9 to mediate poplar drought tolerance. The results of this study provide a theoretical framework for the targeted breeding of drought-tolerant traits in perennial woody plants.
脱落酸（ABA）信号传导与植物对水分亏缺诱导的渗透胁迫的响应有关。然而，其潜在的分子机制仍未阐明。本研究在木本模式植物杨树（毛果杨）中鉴定出了环型E3泛素连接酶环锌指蛋白1（PtrRZFP1）。PtrRZFP1编码一种参与蛋白质泛素化的泛素E3连接酶。PtrRZFP1主要在细胞核和内质网中发挥作用，并受干旱和ABA激活。过表达PtrRZFP1的转基因杨树（35S:PtrRZFP1）对干旱表现出更强的耐受性，而PtrRZFP1基因敲低系（KD-PtrRZFP1）对干旱表现出更高的敏感性。在聚乙二醇和ABA处理下，PtrRZFP1促进气孔保卫细胞中一氧化氮和过氧化氢的产生，最终增强气孔关闭并提高耐旱性。此外，PtrRZFP1与ABA信号传导的核心调节因子A类蛋白磷酸酶2C蛋白PtrPP2C-9发生物理相互作用，并通过泛素化-26S蛋白酶体系统介导其泛素化及最终降解，表明PtrRZFP1正向调节ABA信号通路。此外，过表达PtrPP2C-9的株系对ABA不敏感，且比野生型植物对干旱更敏感，而在35S:PtrRZFP1植物中观察到相反的表型。总体而言，PtrRZFP1负向调节PtrPP2C-9的稳定性以介导杨树的耐旱性。本研究结果为多年生木本植物耐旱性状的定向育种提供了理论框架。
