Glucosyltransferase involved in steroid saponin biosynthesis (PubMed:15821879). Catalyzes the 3-O-glucosylation of steroidal sapogenins, such as diosgenin, nuatigenin and tigogenin (PubMed:15821879). Can glucosylate steroidal alkaloids, such as solanidine, solasodine and tomatidine (PubMed:15821879). nuatigenin + UDP-alpha-D-glucose = H(+) + nuatigenin 3-beta-D-glucopyranoside + UDP diosgenin + UDP-alpha-D-glucose = diosgenin 3-O-beta-D-glucoside + H(+) + UDP tigogenin + UDP-alpha-D-glucose = H(+) + tigogenin 3-O-beta-D-glucopyranoside + UDP solasodine + UDP-alpha-D-glucose = H(+) + solasodine 3-beta-D-glucoside + UDP solanidine + UDP-alpha-D-glucose = H(+) + solanidine 3-O-beta-D-glucopyranoside + UDP tomatidine + UDP-alpha-D-glucose = H(+) + tomatidine 3-O-beta-D-glucopyranoside + UDP Expressed in roots, stems and leaves. Down-regulated after wounding. Belongs to the UDP-glycosyltransferase family.