Involved in auxin biosynthesis (PubMed:18293011, PubMed:28829777, PubMed:29740464). Converts the indole-3-pyruvic acid (IPA) produced by the TAA family to indole-3-acetic acid (IAA) (PubMed:28829777). Seems not able to use tryptamine (TAM) as substrate (PubMed:28829777). Probably responsible for auxin biosynthesis in leaves and involved in the regulation of lateral leaf growth (PubMed:18293011). Required for maintaining water homeostasis and an appropriate root to shoot ratio (PubMed:17619151). Required for the inhibition of root growth by ethylene in etiolated seedlings (PubMed:28829777). Functions downstream of the ethylene-response transcription factor EIL1 (PubMed:28829777). H(+) + indole-3-pyruvate + NADPH + O2 = (indol-3-yl)acetate + CO2 + H2O + NADP(+) Expressed in leaves, young panicles and young kernels (PubMed:17619151). Highly expressed in embryos. Expressed in roots, shoots and panicles (PubMed:18293011). Expressed in root tips, leaves, stems, young stem nodes and developing grains (PubMed:28829777). Induced by ethylene. Narrow and rolled leaf phenotype (PubMed:17619151, PubMed:28829777). Reduced root growth (PubMed:17619151). Tolerance to salt stress (PubMed:28829777). Reduced response to inhibition of root elongation by ethylene (PubMed:28829777). Calli overexpressing YUCCA8 exhibit high levels of auxin, low regeneration frequency, overgrowing roots and abnormal root morphology. Belongs to the FMO family.