Transcriptional activator involved in the sporophytic control of cell wall patterning and gametophytic control of pollen development. May play a role in the control of metabolic pathways regulating cellular transport and lipid metabolism. Forms heterodimers with BZIP18, BZIP43 and VIP1/BZIP51. Expressed in vascular tissues of leaves, stems and siliques, anthers, filaments, tapetum, mature pollen grains, pistil vascular tissues and papillar cells, and funiculi. Pollen morphological defects, reduced pollen germination efficiency and pollen tube growth. Truncated N-terminus. Truncated N-terminus.