Fig. 1
From: WRKY transcription factors: evolution, binding, and action
Scheme of WRKY domain evolution. a Representative WRKY domain (WD) of each (sub)group. The consensus amino acid sequences of WDs from rice. The conserved zinc finger in red; the green R in bold for the conserved R-intron (phase 2), but the R-intron in Chlamydomonas reinhardtii at the position of underlined bold R (I CT line) instead; the light blue V in bold for the conserved V-intron (phase 0) of subgroups IIa and IIb. One of the introns in I NT of C. reinhardtii is at the position of underlined K (phase 2) in bold, however intronless for rice and Arabidopsis I NT WDs. b Hypothetical WD evolution. A hypothetical ancient WD existed as the ancestors of all WRKY genes. The ancient WD diversified to I CT/IIc and IIb structures. The IIa and IIe WDs were deduced from IIb and IIe, respectively. The I NT WD is possibly gained by domain duplication and then subfunctionization. I NT and I CT for N- and C-terminal group I WD, respectively; arrows for the direction of evolution