Transcription factor involved in starch synthesis (PubMed:12953112). Acts as a transcriptional activator in sugar signaling (PubMed:16167901). Interacts specifically with the SURE and W-box elements, but not with the SP8a element (PubMed:12953112). Expressed in endosperm, but not in leaves. Peak of expression 12 days after pollination. Up-regulated by sugar. Expression of barley SUSIBA2 transcription factor in rice yields plants with increased starch content and reduced methane emission. Belongs to the WRKY group I family.