Plays a role in the arabinosylation of cell wall components (PubMed:17401635). Involved in the arabinosylation of extensin proteins in root hair cells. Extensins are structural glycoproteins present in cell walls and its arabinosylation is important for root hair cell development (PubMed:21680836). Expressed in leaf meristem and at points of cauline leaf attachments on the primary stem. Expressed at low levels in siliques. The conserved DXD motif is involved in enzyme activity. Reduced arabinose content in the insoluble cell wall fraction of meristematic region (PubMed:17401635). Reduced root hair length and content of arabinosylated extensins in root cell walls (PubMed:21680836). Belongs to the glycosyltransferase 77 family.