Probable transcription factor (By similarity). Involved in spikelet transition (Probable). Together with SNB, controls synergistically inflorescence architecture and floral meristem establishment via the regulation of spatio-temporal expression of B- and E-function floral organ identity genes in the lodicules and of spikelet meristem genes (PubMed:22003982). Prevents lemma and palea elongation as well as grain growth (PubMed:28066457). May form homodimer (By similarity). Interacts with TPR2/ASP1 (PubMed:26631749). Highly expressed in developing panicles and in young seedlings (PubMed:20017947, PubMed:22003982). Present at low levels at all developmental stages (PubMed:22003982). Detected in developing branch and spikelet meristems at very early stages of inflorescence formation, and is maintained uniformly in the spikelet meristems until floral organs initiation. Present in some floral organ primordia. Target of miR172 microRNA mediated cleavage, particularly during floral organ development. Delayed transition from spikelet meristems to floral meristems and altered floral architecture. The snb osids1 double mutant, lacking both SNB and IDS1, exhibits a decreased number of branches and spikelets within a panicle, as well as a strongly delayed transition to a floral meristem, associated with abnormal spatio-temporal expression of B- and E-function floral organ identity genes in the lodicules and of spikelet meristem genes. Belongs to the AP2/ERF transcription factor family. AP2 subfamily.