Overview of the evolution of WRKY transcription factors. Boxes represent WRKY domains. Red boxes indicate postulated progenitor domains. Blue boxes indicate WRKY domains from present day species. Green boxes indicate FLYWCH, GCM1 and BED zinc finger domains. Conserved introns are shown in red lettering. The four major flowering plant WRKY lineages are shown in large light blue boxes. Currently existing groups of WRKY transcription factors not found in multicellular plants are shown in large light green boxes. The direction of evolution is shown by arrows.