Involved in sporophytic and gametophytic development. Required for normal plant development. During pollen formation, required for the entry of microspores into mitosis and microspore symmetric division. May be required for correct temporal and spatial control of callose deposition during pollen mitosis. During plant growth and development, callose is found as a transitory component of the cell plate in dividing cells, is a major component of pollen mother cell walls and pollen tubes, and is found as a structural component of plasmodesmatal canals. [(1->3)-beta-D-glucosyl](n) + UDP-alpha-D-glucose = [(1->3)-beta-D-glucosyl](n+1) + H(+) + UDP Expressed throughout pollen development with a peak at bicellular pollen stage. Plants develop deformed or collapsed and inviable pollen grains. Belongs to the glycosyltransferase 48 family. Truncated N-terminus.