E3 ubiquitin-protein ligase involved in the positive regulation of abscisic acid-dependent drought stress responses (PubMed:22405823). Involved in the positive regulation of responses to salt and osmotic stresses during seed germination and early seedling development (PubMed:23951086). Possesses E3 ubiquitin ligase activity in vitro (PubMed:22405823, PubMed:23951086). 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 root tips, leaf tips, junction of carpels and pedicels, stigma, anthers, pollen, vasculature of sepals and petals, immature seeds and embryos. Induced by abscisic acid (ABA), and drought and salt stresses. No visible phenotype under normal growth conditions (PubMed:22405823, PubMed:23951086). Mutant plants have decreased sensitivity to abscisic acid (ABA) and reduced tolerance to drought stress (PubMed:22405823). Plants over-expressing RDUF1 display decreased sensitivity to salt and osmotic stresses.