Mediates E2-dependent protein ubiquitination. Plays a role in salicylic acid-mediated negative feedback regulation of salicylic acid (SA) accumulation. May be involved in the overall regulation of SA, benzoic acid and phenylpropanoid biosynthesis. Controls the adaptability to nitrogen limitation by channeling the phenylpropanoid metabolic flux to the induced anthocyanin synthesis. 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. Interacts with UBC8. High expression in roots and stems, medium in seedlings, flowers, rosette and cauline leaves, and very low in siliques. Detected in cotyledons, hypocotyls, pedicel, receptacle, pistil, sepal, filament of stamen and at the two ends of developing siliques. By salicylic acid and benzoic acid. The RING-type zinc finger domain mediates binding to an E2 ubiquitin-conjugating enzyme. Plants show a low-nitrogen-induced early senescence phenotype and an excessive accumulation of salicylic acid after pathogen infection or application of benzoic acid.