Involved in the O-glucosylation of monolignols (alcohol monomers of lignin) (PubMed:11042211, PubMed:15907484, PubMed:24667164). Glucosylates coniferyl alcohol to form coniferyl alcohol 4-O-glucoside (PubMed:15907484, PubMed:24667164). Glucosylates sinapyl alcohol to form sinapyl alcohol 4-O-glucoside (PubMed:11042211, PubMed:15907484, PubMed:24667164). Possesses low activity with sinapate as substrate (PubMed:11042211, PubMed:15907484). (E)-4-coumarate + UDP-alpha-D-glucose = 4-O-(beta-D-glucosyl)-trans-4-coumarate + H(+) + UDP (E)-sinapyl alcohol + UDP-alpha-D-glucose = 4-O-(beta-D-glucosyl)-trans-4-sinapoyl alcohol + H(+) + UDP (E)-coniferol + UDP-alpha-D-glucose = 4-O-(beta-D-glucosyl)-trans-coniferol + H(+) + UDP E-sinapate + UDP-alpha-D-glucose = 4-O-(beta-D-glucosyl)-trans-sinapate + H(+) + UDP (E)-coniferaldehyde + UDP-alpha-D-glucose = 4-O-(beta-D-glucosyl)-4-trans-coniferyl aldehyde + H(+) + UDP (E)-sinapaldehyde + UDP-alpha-D-glucose = 4-O-(beta-D-glucosyl)-4-trans-sinapoyl aldehyde + H(+) + UDP Expressed in seedlings and roots, and at lower levels in flowers and siliques. Belongs to the UDP-glycosyltransferase family.