WRKY family members appear to be involved in the regulation of various physiological programs that are unique to plants, including pathogen defense, senescence and trichome development. In spite of the strong conservation of their DNA-binding domain, the overall structures of WRKY proteins are highly divergent and can be categorized into distinct groups, which might reflect their different functions.The WRKY domain is defined by the conserved amino acid sequence WRKYGQK at its N-terminal end, together with a novel zinc-finger-like motif. Because of the clear binding preference of all characterized WRKY proteins for the same DNA motif, it has been assumed that the WRKY domain, as their only conserved structural feature, constitutes a DNA-binding domain. Indeed, it has recently been shown that an isolated WRKY domain has sequence-specific DNA-binding activity. The divalent metal chelators 1,10-o-phenanthroline and EDTA abolish in vitro DNA binding, which is taken as strong support for a zinc-finger structure within the WRKY domain. However, it has not yet been proven that zinc is actually complexed in the WRKY domain. In addition, nothing is known about the function of the WRKYGQK heptapeptide stretch, the hallmark of this superfamily.