MtWRP1, a Novel Fabacean Specific Gene, Regulates Root Nodulation and Plant Growth in Medicago truncatula.

Wei Chen,Xiaomin Ji,Yingjun Chi,Jinglong Zhang,Yixin Shen,Binqiang Bai

doi:10.3390/genes13020193

Abstract

Fabaceans symbiotically interact with nitrogen-fixing rhizobacteria to form root nodules. Some fabacean specific proteins play important roles in the symbiosis. WRKY-related Protein (WRP) is a novel fabacean specific protein, whose functions have not been well characterized. In this study, MtWRP1 was functionally characterized in Medicago truncatula. It contains a WRKY domain at C-terminal and a novel transmembrane (TM) domain at N-terminal, and its WRKY domain was highly similar to the N-terminal WRKY domain of the group I WRKY proteins. The TM domain was highly homologous to the eukaryotic cytochrome b561 (Cytb561) proteins from birds. Subcellular localization revealed that MtWRP1 was targeted to the Golgi apparatus through the novel TM domain. MtWRP1 was highly expressed in roots and nodules, suggesting its possible roles in the regulation of root growth and nodulation. Both MtWRP1-overexpression transgenic M. truncatula and MtWRP1 mutants showed altered root nodulation and plant growth performance. Specifically, the formation of root nodules was significantly reduced in the absence of MtWRP1. These results demonstrated that MtWRP1 plays critical roles in root nodulation and plant growth.

Highlights

Academic Editors: Mathilde CausseFabacean is an important flowering plant family, containing the essential bean crops and forages
The full-length of MtWRP1 (Medtr5g074200) contained an open reading frame of 984 bp that encoded a predicted protein of 327 amino acid residues with an estimated molecular mass of 37.5 kD and a calculated pI of 9.35
The putative localization signals were indicated by the green box. (B) Alignment of the MtWRP1 WRKY domain sequence with the consensus sequences of the WRKY domains of seven WRKY subfamilies, including the N-terminal (NT) and C-terminal (CT) WRKY domains of group I WRKY proteins

Summary

Introduction

Academic Editors: Mathilde CausseFabacean (legume) is an important flowering plant family, containing the essential bean crops (e.g., soybean, Glycine max) and forages (e.g., alfalfa, Medicago sativa). Fabaceans could establish symbiotic interactions with rhizobia, which can facilitate nitrogen absorption of plants [1,2]. The essential feature of the symbiotic nitrogen fixation system is the formation of inimitable plant root nodules. Nodule formation refers to two closely coordinated processes, infection, and nodule organogenesis [5,6,7] These processes are governed by a number of unique signaling cascades, involving flavonoids and Nod factors, Type III, IV, and VI secretion system effectors, bacterial surface polysaccharides, NCR peptides, phytohormones, CLE and CEP peptides, and small RNAs [8,9,10,11,12,13,14,15]

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Conclusion