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.All known WRKY proteins contain either one or two WRKY domains. They can be classified on the basis of both the number of WRKY domains and the features of their zinc-finger-like motif.Nevertheless, experimental evidence has shown that members of all three groups bind sequence specifically to various W box elements.