Functions as an E3 ligase that promotes polyubiquitination of SPL14/IPA1 for subsequent proteasomal degradation (PubMed:28298520). Regulates plant architecture by modulating SPL14/IPA1 abundance (PubMed:28298520). Promotes the degradation of SPL14/IPA1 in panicles, while it stabilizes SPL14/IPA1 in shoot apices (PubMed:28298520). Ubiquitinates the SPL14/IPA1-mediated complex with 'Lys-48'-linked polyubiquitin in panicles and 'Lys-63'-linked polyubiquitin chains in the shoot apex (PubMed:28298520). 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 SPL14/IPA1. Altered plant architecture, including increased number of tillers, enlarged panicles, and increased grain yield per plant. Extended N-terminus.