Transcription factor that controls embryo growth (PubMed:18567831, PubMed:18849529, PubMed:23318634). Regulates endosperm breakdown and embryonic epidermal development. Regulates the expression of SBT2.4/ALE1 (PubMed:18849529, PubMed:23318634). Involved in embryonic cuticle formation upstream of SBT2.4/ALE1 (PubMed:23318634). Does not seem to be a general regulator of endosperm patterning. May control specific signaling pathways that coordinate embryo invasion and breakdown of surrounding endosperm tissues (PubMed:18849529). Required for the production the embryo sheath, an extracuticular endosperm-derived structure at the surface of the embryo. Acts upstream of KRS (PubMed:28696222). Homodimer. Siliques. Not detected in roots, rosette leaves or flowers. Expressed in endosperm cells. Expressed during seed development (PubMed:18567831). Exclusively expressed in the endosperm of developing seeds (PubMed:18849529). Small and shriveled seeds. Retarded growth of the embryo after the heart stage, but normal morphogenesis and pattern formation of the embryo and endosperm (PubMed:18567831). Shrivelled collapsed seeds (PubMed:18849529).