Involved in auxin biosynthesis. Belongs to the set of redundant YUCCA genes probably responsible for auxin biosynthesis in roots. H(+) + indole-3-pyruvate + NADPH + O2 = (indol-3-yl)acetate + CO2 + H2O + NADP(+) Plant hormone metabolism; auxin biosynthesis. Expressed in root tips and in hydathodes. Expressed in root vasculature and quiescent center, but not in the meristematic zone of the root tip. Up-regulated by high temperature via activation by PIF4. Positively regulated by STY1 and during the day by REV1. Belongs to the FMO family.