The Arabidopsis PARKIN-like E3 ligase ARIADNE5 regulates plant development by targeting TCP4 for degradation

Plant organ size and morphology are crucial agronomic traits that influence both plant fitness and crop productivity. The TEOSINTE BRANCHED 1/CYCLOIDEA/PCF (TCP) transcription factors play pivotal roles in shaping plant morphology, yet the precise regulatory mechanisms governing their activity remain incompletely understood. Here, we identify the PARKIN-like E3 ubiquitin ligase ARIADNE5 (ARI5) as a key regulator of TCP4 stability, mediating its ubiquitination and subsequent degradation. We identified ARI5 interacted with TCP4 using immunoprecipitation-mass spectrometry (IP-MS). The ari5 ari7 double mutant displays flatter leaves, shorter gynoecia, accelerated cotyledon opening in darkness, and earlier flowering. These phenotypes are strikingly opposite to those observed in tcp -deficient mutants. ARI5 and its close homolog ARI7 exhibit overlapping expression patterns with TCP4 , and their encoded proteins colocalize with TCP4 in the nucleus. ARI5 possesses E3 ubiquitin ligase activity, and promotes the ubiquitin-dependent degradation of TCP4. Our findings not only establish ARI5 as a critical regulator of plant organ morphology but also uncover a post-translational regulatory mechanism that fine-tunes TCP4 activity and thus cell division during organ morphogenesis through proteasomal degradation, highlighting the evolutionary conservation of PARKIN-like E3 ligases in modulating cell division across plants and humans.