E3 ubiquitin-protein ligase that mediates the formation of 'Lys-63'-linked ubiquitin chains. Regulates apical dominance by acting on the auxin transport proteins abundance (PubMed:17586653). Together with RGLG5, mediates the ubiquitination and subsequent proteasomal degradation of the target protein PP2CA. Functions as positive regulator of abscisic acid (ABA) signaling through ABA-dependent degradation of PP2CA, a major inhibitor of ABA signaling (PubMed:27577789). Acts as a negative regulator of drought stress response (PubMed:22095047). 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. Interacts with the heterodimer UBC35/UEV1B (PubMed:17586653). Interacts with ERF053 (PubMed:22095047). Interacts with PP2CA (PubMed:27577789). Ubiquitously expressed. N-myristoylated. No visible phenotype; due to the redundancy with RGLG2 (PubMed:17586653, PubMed:22095047). Rglg1 and rglg2 double mutants show a complete loss of apical dominance (PubMed:17586653). The double mutant seedlings rglg1 and rglg2 exhibit a dehydration-tolerant phenotype (PubMed:22095047).