E3 ubiquitin protein ligase that acts as positive regulator of sugar signaling during early seedling development. Possesses E3 ligase activity in vitro. 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. Expressed in roots, stems, leaves, flowers and siliques. Resistance to high concentrations of exogenous glucose and sucrose on early seedling development.