Identification of WRKY Gene Family from Dimocarpus longan and Its Expression Analysis during Flower Induction and Abiotic Stress Responses

Dengwei Jue,Xuelian Sang,Shengyou Shi,Chengming Liu,Bo Shu,Yicheng Wang,Liqin Liu,Jianghui Xie

doi:10.3390/ijms19082169

Abstract

Longan is an important fruit tree in the subtropical region of Southeast Asia and Australia. However, its blooming and its yield are susceptible to stresses such as droughts, high salinity, and high and low temperature. To date, the molecular mechanisms of abiotic stress tolerance and flower induction in longan have not been elucidated. WRKY transcription factors (TFs), which have been studied in various plant species, play important regulatory roles in plant growth, development, and responses to stresses. However, there is no report about WRKYs in longan. In this study, we identified 55 WRKY genes with the conserved WRKY domain and zinc finger motif in the longan genome. Based on the structural features of WRKY proteins and topology of the phylogenetic tree, the longan WRKY (DlWRKY) family was classified into three major groups (I–III) and five subgroups (IIa–IIe) in group II. Tissue expression analysis showed that 25 DlWRKYs were highly expressed in almost all organs, suggesting that these genes may be important for plant growth and organ development in longan. Comparative RNA-seq and qRT-PCR-based gene expression analysis revealed that 18 DlWRKY genes showed a specific expression during three stages of flower induction in “Sijimi” (“SJ”), which exhibited the “perpetual flowering” (PF) habit, indicating that these 18 DlWRKY genes may be involved in the flower induction and the genetic control of the perpetual flowering trait in longan. Furthermore, the RT-qPCR analysis illustrated the significant variation of 27, 18, 15, 17, 27, and 23 DlWRKY genes under SA (Salicylic acid), MeJA (Methyl Jasmonate), heat, cold, drought, or high salinity treatment, respectively, implicating that they might be stress- or hormone-responsive genes. In summary, we systematically and comprehensively analyzed the structure, evolution, and expression pattern of the DlWRKY genes. The results presented here increase our understanding of the WRKY family in fruit trees and provide a basis for the further elucidation of the biological function of DlWRKY genes in longan.

Highlights

Longan (Dimocarpuslongan Lour.) is an important subtropical fruit tree in the family Sapindaceae, which is grown in many subtropical and tropical countries with most of the production in SoutheastAsia and Australia [1]
55 determined the expression profiles of longan WRKY (DlWRKY) genes were determined in the longan genome (Table 1)
After the domain scanning and sequence alignment, 55 DlWRKY genes were determined in the longan genome

Summary

Introduction

Longan (Dimocarpuslongan Lour.) is an important subtropical fruit tree in the family Sapindaceae, which is grown in many subtropical and tropical countries with most of the production in SoutheastAsia and Australia [1]. Longan (Dimocarpuslongan Lour.) is an important subtropical fruit tree in the family Sapindaceae, which is grown in many subtropical and tropical countries with most of the production in Southeast. Biennial bearing is the most serious problem that affects longan fruit products. Among the factors that affect D. longan fruit yield, the difficulty and unstableness to blossom is one of the most challenging problems [2]. The study of the molecular regulatory mechanisms of flower induction and abiotic stress tolerance in longan is important for understanding and solving the problems associated with fruit yield. Due to the long generation time and lack of genome information, knowledge of the molecular regulatory mechanisms of flower induction and abiotic stress tolerance in longan is scarce

Results

Discussion

Conclusion