Transcription activator of small-nuclear RNA genes (snRNA), which have essential roles in pre-mRNA splicing and rRNA processing. Essential protein involved in the establishment of apical meristems and organ primordia, embryogenesis, cell differentiation and cell proliferation, probably by modulating the establishment of auxin gradients. Participates in the control of competence in cell proliferation; required for the reinitiation of the progression of the cell cycle and subsequent cell proliferation during cell redifferentiation leading to callus formation, especially during the first day of dedifferentiation (e.g. callus, root and shoot formation from root and hypocotyl explants). Part of the SNAPc complex. Expressed in seedlings, apical meristems, developing leaves, roots, stipules and flowers. In young seedlings, accumulates in shoot and root apical meristems (SAM and RAM, respectively), leaf primordia, and root stele tissues. In roots, high levels throughout young root primordia that later decrease at the arrest of cell division, and finally increase again when the apical meristem become activated. In young developing leaves, present in guard cells, vascular tissues, trichomes, and trichome support cells to be later expressed uniformly in the lamina. Gradually restricted to the leaf margin and fades out in fully expanded leaves. In roots, detected in apices, stele tissues, and lateral root primordia. In flowers, first observed over the floral bud, and later restricted to vascular tissues in developing floral organs, except for the pistil, where the expression is ubiquitous. In mature flowers, disappears progressively from the pistil, but accumulates in mature pollen and the filaments. Also present in pedicels. In pollinated pistils, highly expressed in ovaries that contain developing embryos. Present throughout embryogenesis, particularly in the lower half of the embryo at the heart-shaped stage and in the radicle RAM region at the cotyledonary stage. Transiently induced by auxin (2,4-D), with a synergistic action of auxin and cytokinin on transcript levels. Lethal. Belongs to the SNAPC3/SRD2 family.