Transcriptome-Wide Identification ofWRKY Transcription Factors andTheir Expression Profiles under Different Types of Biological and Abiotic Stress inPinus massoniana Lamb.

Sheng Yao,Fan Wu,Kongshu Ji,Qingqing Hao

doi:10.3390/genes11111386

Abstract

Pinus massoniana Lamb, an economically important conifer tree, is widely distributed in China. WRKY transcription factors (TFs) play important roles in plant growth and development, biological and abiotic stress. Nevertheless, there is little information about the WRKY genes in P. massoniana. By searching for conserved WRKY motifs in transcriptomic RNA sequencing data for P. massoniana, 31 sequences were identified as WRKY TFs. Then, phylogenetic and conserved motif analyses of the WRKY family in P. massoniana, Pinus taeda and Arabidopsis thaliana were used to classify WRKY genes. The expression patterns of six PmWRKY genes from different groups were determined using real-time quantitative PCR for 2-year-old P. massoniana seedings grown in their natural environment and challenged by phytohormones (salicylic acid, methyl jasmonate, or ethephon), abiotic stress (H2O2) and mechanical damage stress. As a result, the 31 PmWRKY genes identified were divided into three major groups and several subgroups based on structural and phylogenetic features. PmWRKY genes are regulated in response to abiotic stress and phytohormone treatment and may participate in signaling to improve plant stress resistance. Some PmWRKY genes behaved as predicted based on their homology with A. thaliana WRKY genes, but others showed divergent behavior. This systematic analysis lays the foundation for further identification of WRKY gene functions to aid further exploration of the functions and regulatory mechanisms of PmWRKY genes in biological and abiotic stress in P. massoniana.

Highlights

Plants are capable of managing various types of stress during their life cycle and have developed several mechanisms to adapt to biotic and abiotic stress
The WRKY gene family may be crucial for the remarkable tolerance of P. massoniana, and we identified 31 PmWRKY genes based on RNA-seq, and the classification, domain structures, subcellular localization prediction, and expression patterns of PmWRKYs were analysed using bioinformatic methods
Our study showed that six PmWRKYs (PmWRKY3, PmWRKY7, PmWRKY13, PmWRKY15, PmWRKY17 and PmWRKY30) responded to at least two types of stress, among which PmWRKY3 was significantly elevated by induction with methyl jasmonate (MeJA), salicylic acid (SA), ETH, H2 O2, and mechanical stress

Summary

Introduction

Plants are capable of managing various types of stress during their life cycle and have developed several mechanisms to adapt to biotic and abiotic stress. Families of transcription factors (TFs) play an important role in stress response by regulating the expression of target genes, interacting with specific cis-acting elements present in their promoter regions, and acting as activators or repressors in plant stress responses [1,2]. WRKY transcription factors (TFs) constitute one of the largest families of transcription regulators in plants. The most prominent feature of the WRKY protein is its highly conserved WRKY domain, which is composed of 60 amino acids and has a “WRKYGQK” amino acid motif at the N-terminus [3,4]. The WRKY protein contains a C2H2- or C2HC-type zinc finger structure [5]. Based on structural differences in the WRKY domain and zinc finger, WRKY TFs have

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