Identification of Populus trichocarpa WRKY Gene Family and Its’ Response to Drought Stress
ZHOU Jing#, ZENG Meiyan#, AN Xinmin*
WRKY is a widely studied plant transcription factor in recent years. Its amino (N-) terminus contains a highly conserved heptapeptide WRKYGQK, which can interact with the cis-acting element W-box(T)TGAC(C/T)] specific binding occurs, thereby regulating the expression of downstream target genes. In this study, the bioinformatics method was used to identify the WRKY transcription factors of poplar, sequence analysis, chromosomal localization, domain analysis, phylogenetic analysis and tissue expression analysis. The result suggested that 122 members of the poplar WRKY family were identified, and classed into 3 major categories (34 class I members, 78 class II members, and 10 class III members). Chromosomal localization analysis indicated that the number of WRKY genes located on each chromosome was different, and no distribution on chromosome 9, it presented an uneven distribution. Further phylogenetic analysis revealed that the WRKY family members formed three major clades. In addition, combined with gene structure analysis, the WRKY genes located in the same clades usually have similar motifs and exons/intron structure pattern, indicating the functional similarity of WRKY gene. Finally, we performed analysis, found that 62 family members were involved in response to drought stress, it can be divided into five gene clusters (I, II, III, IV, V), and most of the four clusters I, III, IV and V are significantly up-regulated under drought stress for about 8 h. Class II was significantly up-regulated during drought stress for 2 to 4 h, while PtWRKY70, PtWRKY81, PtWRKY104, and PtWRKY108 were significantly down-regulated after drought stress treatment, it indicates that WRKY gene plays an important role in response to drought stress. In this study, we performed a comprehensive indentification of poplar WRKY gene family, this work enriched our understanding of WRKY gene family, and provided valuable candidate genes information for the poplar drought-resistant breeding.
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