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Updated: Jun 12, 2025

Functional Characterization of RING-Type E3 Ubiquitin Ligases In Vitro and In Planta
Published on: December 5, 2019
The ubiquitin E3 ligase RZFP1 affects drought tolerance in poplar by mediating the degradation of the protein
Fang He1, Meng-Xue Niu2, Ting Wang1
1National 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.
Abstract:
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.
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