Involved in the biosynthesis of sterol glucosides. Catalyzes the synthesis of steryl glycosides (SGs) and acyl steryl glycosides (ASGs) which are the most abundant sterol derivatives in higher plants. Can act on several sterols like sitosterol, campesterol and stigmasterol. Is required for embryonic development, seed suberin accumulation, cutin formation and flavanoid accumulation in the seed coat. Both UGT80A2 and UGT80B1 are required for the normal production of SGs and ASGs in seeds. a sterol + UDP-alpha-D-glucose = a sterol 3-beta-D-glucoside + H(+) + UDP Expressed in developing seeds, seedlings, leaves and around the apical tip of cotyledons. In embryo, expressed in the seed coat and cotyledons. Reduced growth rates. Altered embryonic development, seed suberin accumulation, cutin formation in the seed coat and reduced seed size. Lack of flavanoid accumulation in the seed coat (transparent testa phenotype). Belongs to the glycosyltransferase 28 family.