Rapid systemic accumulation of transcripts encoding a tobacco WRKY transcription factor upon wounding
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An immediate-early, transiently activated wound-responsive gene was identified in tobacco by fluorescent differential display screening. The full-length cDNA encodes a polypeptide of 356 amino acids with a relative molecular mass of 39,082 Da. The deduced amino acid sequence shows two characteristic features; a leucine-zipper motif found in the more N-terminal region and a WRKY domain containing a zinc-finger motif located in the central region. The gene was designated as wizz (wound-induced leucine zipper zinc finger). Northern analysis showed that upon wounding wizz transcripts were locally and systemically accumulated within 10 min, reached a maximum level by 30 min, and decreased thereafter to the basal level. Analyses of a WIZZ-GFP fusion protein clearly indicated that WIZZ is a nuclear factor. WIZZ specifically binds to sequences containing two TTGAC core motifs that are separated by a spacer of appropriate length. The binding activity was dependent on bivalent cations, most probably zinc. In transient reporter assays, however, WIZZ did not show transactivation activity in tobacco suspension cells, suggesting that it functions together with other components. The results indicate that WIZZ is a new transcription factor which participates in early stages of the wound response.
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