title: Genome-wide survey and characterization of the WRKY gene family in Populus trichocarpa.
abstract: WRKY transcription factors participate in diverse physiological and developmental processes in plants. They have highly conserved WRKYGQK amino acid sequences in their N-termini, followed by the novel zinc-finger-like motifs, Cys₂His₂ or Cys₂HisCys. To date, numerous WRKY genes have been identified and characterized in a number of herbaceous species. Survey and characterization of WRKY genes in a ligneous species would facilitate a better understanding of the evolutionary processes and functions of this gene family. In this study, 104 poplar WRKY genes (PtWRKY) were identified in the latest poplar genome sequence. According to their structural features, the predicted members were divided into the previously defined groups I-III, as described in rice. In addition, chromosomal localization of the genes demonstrated that there might be WRKY gene hot spots in 2.3 Mb regions on chromosome 14. Furthermore, approximately 83% (86 out of 104) WRKY genes participated in gene duplication events, including 69% (29 out of 42) gene pairs which exhibited segmental duplication. Using semi-quantitative RT-PCR, the expression patterns of subgroup III genes were investigated under different stresses [cold, drought, salinity and salicylic acid (SA)]. The data revealed that these genes presented different expression levels in response to various stress conditions. Expression analysis exhibited PtWRKY76 gene induced markedly in 0.1 mM SA or 25% PEG-6000 treatment. The results presented here provide a fundamental clue for cloning specific function genes in further studies and applications.
  
  
  CONCLUSIONS
  This study identified 104 poplar WRKY genes and demonstrated WRKY gene hot spots on chromosome 14. Furthermore, semi-quantitative RT-PCR showed variable stress responses in subgroup III.
authors.affiliation: Lab of Modern Biotechnology, School of Forestry and Landscape Architecture, Anhui Agricultural University, Hefei 230036, China.
authors.forename: Hongsheng
authors.initials: H
authors.lastname: He
authors.forename: Qing
authors.initials: Q
authors.lastname: Dong
authors.forename: Yuanhua
authors.initials: Y
authors.lastname: Shao
authors.forename: Haiyang
authors.initials: H
authors.lastname: Jiang
authors.forename: Suwen
authors.initials: S
authors.lastname: Zhu
authors.forename: Beijiu
authors.initials: B
authors.lastname: Cheng
authors.forename: Yan
authors.initials: Y
authors.lastname: Xiang
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D002874:Chromosome Mapping; D017124:Conserved Sequence; D019143:Evolution, Molecular; D005091:Exons; D020440:Gene Duplication; D018506:Gene Expression Regulation, Plant; D018745:Genome, Plant; D007438:Introns; D008969:Molecular Sequence Data; D005810:Multigene Family; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics; D032107:Populus / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D010940:Plant Proteins; D014157:Transcription Factors