A role for flavin monooxygenase-like enzymes in auxin biosynthesis

Although auxin is known to regulate many processes in plant development and has been studied for over a century, the mechanisms whereby plants produce it have remained elusive. Here we report the characterization of a dominant Arabidopsis mutant,yucca, which contains elevated Levels of free auxin. YUCCA encodes a flavin monooxygenase-like enzyme and belongs to a family that includes at Least nine other homologous Arabidopsis genes, a subset of which appears to have redundant functions, Results from tryptophan analog feeding experiments and biochemical assays indicate that YUCCA catalyzes hydroxylation of the amino group of tryptamine, a rate-limiting step in tryptophan-dependent auxin biosynthesis.