Transcription factor (PubMed:22408071). Involved in spikelet transition and development (PubMed:22408071). Prevents lemma and palea elongation as well as grain growth (PubMed:22408071). Required for seed shattering through specifying abscission zone (AZ) development (PubMed:22408071). May form homodimer. Expressed in seedlings, leaves, stems, nodes, sheaths, panicles and young spikelets. Accumulates in the spikelet abscission zone (AZ) via a positive regulation by the transcription factor SH4. In developing panicles, highly expressed in the spikelet abscission zone (AZ) and the inner floral organs of 2 mm long spikelets. Later present at weak levels in the apiculus as well as in the palea and lemma to progressively fades out in 8 mm long spikelets. Several spikelet and inflorescence developmental defects, including altered florets palea and lemma structures, abnormal numbers, size, appearance, and identities of floral organs, reduced primary branches number, and longer and fewer grains associated with a loss of grain shattering. Crook-neck-like rachilla between the sterile lemmas and the rudimentary glumes in place of the spikelet abscission zone (AZ). Belongs to the AP2/ERF transcription factor family. AP2 subfamily.