Abstract
As a superfamily of transcription factors, the tryptophan-arginine-lysine-tyrosine (WRKY) transcription factors have been found to be essential for abiotic and biotic stress responses in plants. Currently, only 76 WRKY transcription factors in wheat could be identified in the NCBI database, among which only a few have been functionally analyzed. Herein, a total of 188 WRKY transcription factors were identified from the wheat genome database, which included 123 full-length coding sequences, and all of them were used for detailed evolution studies. By bioinformatics analysis, a WRKY transcription factor, named TaWRKY146, was found to be the homologous gene of AtWRKY46, overexpression of which leads to hypersensitivity to drought and salt stress in Arabidopsis. Consequently, the full length of TaWRKY146 was cloned, and the expression levels of TaWRKY146 were found significantly up-regulated in the leaves and roots of wheat seedlings, which were subjected to osmotic stress. Overexpression of TaWRKY146 in Arabidopsis was shown to enhance drought tolerance by the induction of stomatal closure that reduced the transpiration rate. All these results provide a firm foundation for further identification of WRKY transcription factors with important functions in wheat.
Highlights
Tryptophan-arginine-lysine-tyrosine (WRKY) transcription factors are one of the largest families of transcriptional regulators in plants
The coding sequences (CDS) and protein sequences of WRKY transcription factors from T. urartu and A. tauschii were reported in our previous studies (Ma et al, 2014, 2015)
Chromosomes 6 and 7 contained a few TaWRKYs, as in the case of T. urartu and A. tauschii (Ma et al, 2014, 2015), whereas chromosome 5 contained the highest density of TaWRKYs, with more than 10 TaWRKYs in all the three genomes (Supplementary Data Sheet 2)
Summary
Tryptophan-arginine-lysine-tyrosine (WRKY) transcription factors are one of the largest families of transcriptional regulators in plants. The WRKY proteins contain one or two conserved WRKY domains of about 60 amino acids. Based on their features, the WRKY transcription factors are divided into three main groups. Since the identification of the first WRKY transcription factor in sweet potato (Ishiguro and Nakamura, 1994), a large number of WRKY transcription factors have been identified in different plants, several of which were reported to be involved in the responses to abiotic and biotic stress and in phytohormone-mediated signal transduction in plants. In Arabidopsis, 61 WRKY transcription factors (AtWRKYs) were first identified by Eulgem et al (2000), and were named sequentially from AtWRKY1 to AtWRKY61.
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