2010 Volume 27 Issue 2 Pages 121-129
WRKY genes encode proteins which belong to a large family of transcription factors that are involved in various developmental and physiological processes, response to pathogen infections and wound stress in plants. The molecular characteristics of WRKY genes involved in these are becoming clear in model plants, like Arabidopsis. However, knowledge of WRKY genes in other plants, for instance vegetable, is still not enough. In the present studies, using a yeast one-hybrid system we isolated a cDNA from a spinach cDNA library and characterized its function. The cDNA, designated SoWRKY1, encodes a putative polypeptide of 362 amino acids which is highly homologous to Arabidopsis WRKY40 (AtWRKY40). The putative primary structure of SoWRKY1 contains a single WRKY domain of Cys2His2 zinc finger motif and a potential nuclear localization signal (NLS), whose structure is characteristic of group IIa type WRKY protein. SoWRKY1-sGFP fusion protein was localized to the nucleus when the protein was expressed in onion epidermal cells. SoWRKY1 showed high binding affinity to DNA molecules containing TTGAC(C/T) W-box sequences and transcriptional activation activity in yeast. SoWRKY1 transcripts in spinach leaves were transiently induced by wounding treatment and salicylic acid (SA). The transcripts accumulated following treatment with cycloheximide (CHX), a protein biosynthesis inhibitor. Functional analysis of SoWRKY1 in vivo was performed by overexpression in Arabidopsis, and pathogenesis-related PR1 and PR2 gene expression level increased in the transgenic plants. These results suggest that SoWRKY1 might be involved as a transcription factor in defense-related signaling transduction pathways of spinach.
