Genome-wide analysis of WRKY transcription factors in wheat (Triticum aestivum L.) and differential expression under water deficit condition

Background. WRKY proteins which comprise one of the largest transcription factor (TF) families in the plant kingdom, play crucial roles in plant development and stress responses. Despite several studies on WRKYs in wheat (Triticum aestivum L.), functional annotation information about wheat WRKYs is limited. Results. Here, 171 TaWRKY TFs were identified from the whole wheat genome and compared with proteins from 19 other species',representing nine major plant lineages. A phylogenetic analysis, coupled with gene structure analysis and motif determination, divided these TaWRKYs into seven subgroups (Group I, IIa-e, and III). Chromosomal location showed that most TaWRKY genes were enriched on four chromosomes, especially on chromosome 3B. In addition, 85 (49.7%) genes were either tandem (5) or segmental duplication (80), which suggested that though tandem duplication has contributed to the expansion of TaWRKY family, segmental duplication probably played a more pivotal role. Analysis of cis-acting elements revealed putative functions of WRKYs in wheat during development as well as under numerous biotic and abiotic stresses. Finally, the expression of TaWRKY genes in flag leaves, glumes, and lemmas under water-deficit condition were analyzed. Results showed that different TaWRKY genes preferentially express in specific tissue during the grain-filling stage. Conclusion. Our results provide a more extensive insight on WRKY gene family in wheat, and also contribute to the screening of more candidate genes for further investigation on function characterization of WRKYs under various stresses.