Identification of the group IIa WRKY subfamily and the functional analysis of GhWRKY17 in upland cotton (Gossypium hirsutum L.).

Lijiao Gu,Junji Su,Yaning Guo,Hengling Wei,Hantao Wang,Shuxun Yu,Libei Li,Meng-Xiang Sun

doi:10.1371/journal.pone.0191681

Abstract

WRKY transcription factors play important roles in plant defense, stress response, leaf senescence, and plant growth and development. Previous studies have revealed the important roles of the group IIa GhWRKY genes in cotton. To comprehensively analyze the group IIa GhWRKY genes in upland cotton, we identified 15 candidate group IIa GhWRKY genes in the Gossypium hirsutum genome. The phylogenetic tree, intron-exon structure, motif prediction and Ka/Ks analyses indicated that most group IIa GhWRKY genes shared high similarity and conservation and underwent purifying selection during evolution. In addition, we detected the expression patterns of several group IIa GhWRKY genes in individual tissues as well as during leaf senescence using public RNA sequencing data and real-time quantitative PCR. To better understand the functions of group IIa GhWRKYs in cotton, GhWRKY17 (KF669857) was isolated from upland cotton, and its sequence alignment, promoter cis-acting elements and subcellular localization were characterized. Moreover, the over-expression of GhWRKY17 in Arabidopsis up-regulated the senescence-associated genes AtWRKY53, AtSAG12 and AtSAG13, enhancing the plant’s susceptibility to leaf senescence. These findings lay the foundation for further analysis and study of the functions of WRKY genes in cotton.

Highlights

Throughout their life cycle, plants exhibit a set of complex adjustment mechanisms to perceive and respond to various physiological and developmental signals
The 15 group IIa GhWRKYs were mainly scattered on chromosomes 5, 6 and 7 and ranged from 140 to 1442 amino acids in protein length
We explored the roles of group IIa WRKY genes in leaf senescence

Summary

Introduction

Throughout their life cycle, plants exhibit a set of complex adjustment mechanisms to perceive and respond to various physiological and developmental signals. Among these diverse adjustment mechanisms, transcriptional regulation mechanisms, which are mainly executed by transcription factors (TFs), play important roles [1]. Since the first WRKY gene, SPF1, was reported in sweet potato [3], increasing numbers of WRKY genes have been reported in various species, including Arabidopsis thaliana, Gossypium hirsutum, Oryza sativa, Ricinus communis, Manihot esculenta and Cucumis sativus [4,5,6,7,8,9]. WRKY TFs were named for their conserved WRKY domain, which consists of approximately 60 amino acids containing a conserved WRKYGQK core sequence and a zinc finger-.

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