Transcriptome-Wide Identification of Salt-Responsive Members of the WRKY Gene Family in Gossypium aridum

Abstract

WRKY transcription factors are plant-specific, zinc finger-type transcription factors. The WRKY superfamily is involved in abiotic stress responses in many crops including cotton, a major fiber crop that is widely cultivated and consumed throughout the world. Salinity is an important abiotic stress that results in considerable yield losses. In this study, we identified 109 WRKY genes (GarWRKYs) in a salt-tolerant wild cotton species Gossypium aridum from transcriptome sequencing data to elucidate the roles of these factors in cotton salt tolerance. According to their structural features, the predicted members were divided into three groups (Groups I–III), as previously described for Arabidopsis. Furthermore, 28 salt-responsive GarWRKY genes were identified from digital gene expression data and subjected to real-time quantitative RT-PCR analysis. The expression patterns of most GarWRKY genes revealed by this analysis are in good agreement with those revealed by RNA-Seq analysis. RT-PCR analysis revealed that 27 GarWRKY genes were expressed in roots and one was exclusively expressed in roots. Analysis of gene orthology and motif compositions indicated that WRKY members from Arabidopsis, rice and soybean generally shared the similar motifs within the same subgroup, suggesting they have the similar function. Overexpression-GarWRKY17 and –GarWRKY104 in Arabidopsis revealed that they could positively regulate salt tolerance of transgenic Arabidopsis during different development stages. The comprehensive data generated in this study provide a platform for elucidating the functions of WRKY transcription factors in salt tolerance of G. aridum. In addition, GarWRKYs related to salt tolerance identified in this study will be potential candidates for genetic improvement of cultivated cotton salt stress tolerance.

WRKY transcription factors in plant responses to stresses

“…Whole‐genome sequencing of other plant species, especially model plants, enabled the identification of more WRKY genes in plants. There are 197, 100, and 74 WRKY superfamily members in Glycine max, Oryza sativa , Arabidopsis , Brassica napus, and Fragaria vesca, respectively (Rushton et al ; Fan et al ; He et al ; Wei et al ). The expression of WRKY TFs is induced rapidly when the plants are exposed to a variety of stresses or defensive signals including salicylic acid (SA) or other molecules.…”

GarWRKY5, a Member of the WRKY Transcription Factor Gene Family from a Diploid Cotton Species (Gossypium aridum L.), Is Involved in Salt Stress Response

“…To study the physiological response of GarWRKY5-overexpressing Arabidopsis plants to salt stress, the three transgenic lines (GarWRKY5-1, 6,14) were selected to further analyze the activities of SOD and POD in leaves of WT and transgenicplants. The SOD activity of transgenic plants was significantly higher than that of WT plants with or without salt stress.…”

“…However, the molecular mechanisms underlying cotton tolerance to salt stress are still not fully understood due to the complex nature of this response. With the release of the Gossypium genome sequence [8][9][10], genome-wide identification of WRKY family genes has been conducted in G. raimondii, G.arboreum and G. aridum [11][12][13][14]. Several studies have suggested the importance of specific WRKYs in the transcriptional regulation of saltrelated genes in cotton.…”

“…In a previous study, 109 GarWRKYs gene were identified in a salt-tolerant wild cotton species, Gossypium aridum, based on transcriptome sequencing data; meanwhile, 28 salt-responsive GarWRKY genes were identified from transcriptome data and real-time quantitative PCR analysis [14].…”

In silico genome-wide identification and phylogenetic analysis of the WRKY transcription factor family in sweet orange (Citrus sinensis)

“…CitsWRKY genes were blasted against each other and those presenting 80% coverage and 70% identity were considered to represent gene duplications (Lopes-Caitar et al, 2013;Fan et al, 2015). The Plant Genome Duplication Database (PGDD; http://chibba.agtec.uga.edu/duplication/) was utilized to identify orthologous WRKY genes in A. thaliana and C. sinensis.…”