E3 ubiquitin-protein ligase that may be involved in xylem development. S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + N(6)-ubiquitinyl-[acceptor protein]-L-lysine. Protein modification; protein ubiquitination. Highly expressed in stems. Expressed in root xylem and seed coat. The RING-type zinc finger domain is required for E3 ligase activity. No visible phenotype under normal growth conditions.