Involved in sporophytic and gametophytic development. Required for normal plant development and for the proper accumulation of callose at cell plates, cll walls and plasmodesmata. During pollen formation, required for the entry of microspores into 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. Required for proper cell division and tissue patterning throughout plant organs, including stomatal patterning. [(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 at mature pollen stage. Seedling lethality with severe dwarfism. Plants develop collapsed and inviable pollen grains. Belongs to the glycosyltransferase 48 family.