UC Davis

Strigolactones (SLs) are a recently discovered class of endogenous plant hormones that regulate many integral traits such as leaf senescence and root elongation while also functioning as exuded signaling molecules. In pea (Pisum sativum), key players of this hormone pathway include RMS3 (an α/β-fold hydrolase) and PsMAX2 (the F-box component of an SCF E3 ubiquitin ligase module) that coordinate SL-dependent degradation of transcriptional repressors. Strikingly, RMS3 functions as both the SL receptor and an active serine hydrolase that hydrolyzes SLs after they are perceived. This characteristic has raised the questions of whether SL hydrolysis or its mere perception is required for signal propagation, and how exactly the coordination of PsMAX2-RMS3 is related to SL hydrolysis. Here, we elucidate the first crystal structure of RMS3, investigate its enzymatic function by generating two catalytic mutants, and study their effects in SL signaling in vitro. The data uncovered in this work hold the potential to broadly impact research into SL perception and signaling in legumes and beyond.