Group Ia: two WRKY domains, each with a C2H2 zinc finger or one with a C2 and the other with a C2H2 finger;
Group Ib: two WRKY domains, each with a C2HC zinc finger;
Group II: one WRKY domain with a C2H2 finger;
Group III: one WRKY domain with a C2HC finger;
Group IV: contains the WRKY motif, but lacks a complete (C2XX, C2HX, C2-- or C---); they may represent pseudogenes
or errors in sequencing and assembling.

References:
Rice WRKY Woking Group (2012) Rice 5:3.
Rushton et al. (2010) Trends in Plant Sci. 15, 247-258.
Ross et al. (2007) J. Integr. Plant Biol. 49, 827-842.
Xie et al. (2005) Plant Physiol. 137, 176-189.
Zhang et al. (2004) Plant Physiol. 134, 1500-1513.