Modulates seed size by negatively regulating the cellularization of syncytial endosperm (PubMed:12692325, PubMed:20545893). May function by binding and modulating the activity of WRKY10 transcription factor (PubMed:20545893). Interacts with WRKY10 (PubMed:20545893). Interacts with MPK6 (PubMed:24750137). Expressed both in the unfused polar nuclei and in the fused polar nucleus in the central cell before fertilization, in the syncytial endosperm after fertilization and in the endosperm nuclei. A number of isoforms are produced. According to EST sequences. Reduced seed size and early endosperm cellularization.