Characterization of WRKY transcription factors in Solanum lycopersicum reveals collinearity and their expression patterns under cold treatment

WRKY transcription factors play an important role in cold defense of plants. However, little information is available about the cold-responsive WRKYs in tomato (Solanum lycopersicum). In the present study, a complete characterization of this gene family was described. Eighty WRKY genes in the tomato genome were identified. Almost all WRKY genes contain putative stress-responsive cis-elements in their promoter regions. Segmental duplications contributed significantly to the expansion of the SIWRKY gene family. Transcriptional analysis revealed notable differential expression in tomato tissues and expression patterns under cold stress, which indicated wide functional divergence in this family. Ten WRKYs in tomato were strongly induced more than 2-fold during cold stress. These genes represented candidate genes for future functional analysis of WRKYs involved in the cold-related signal pathways. Our data provide valuable information about tomato WRKY proteins and form a foundation for future studies of these proteins, especially for those that play an important role in response to cold stress. (C) 2015 Elsevier Inc. All rights reserved.