Transcription factor. Interacts specifically with the W box (5'-(T)TGAC[CT]-3'), a frequently occurring elicitor-responsive cis-acting element (By similarity). Modulates seed size by negatively regulating the cellularization of syncytial endosperm (PubMed:16293693). Interacts with IKU1. Expressed in male gametophytes (pollen) and in the endosperm of fertilized ovules. Expressed in the endosperm of embryo from the two nuclei stage to the late globular embryo stage, including the endosperm cellularization time. Belongs to the WRKY group I family.