Regulates the arrest of dispersed meristematic cells during lamina development. Interacts with AFPH2/NINJA. First detected at the tip of developing leaf, followed by a tip-to-base progression of the expression. Plants lacking both TIFY4A and TIFY4B have larger leaves and cotyledon laminae, a dome-shaped leaf curvature and shortened siliques. Redundant with TIFY 4B/PPD2. Belongs to the TIFY/JAZ family.