Involved in auxin biosynthesis in anthers. H(+) + indole-3-pyruvate + NADPH + O2 = (indol-3-yl)acetate + CO2 + H2O + NADP(+) Highly expressed in anthers at stage 9 of development, before pollen mitotic divisions. Repressed by the transcription factor OSH1 during anther development (PubMed:29915329). Reduction of auxin levels at late stage of anther development, after meiosis of microspore mother cells, is necessary for normal anther dehiscence and seed setting (PubMed:29915329). Plants overexpressing YUCCA4 are male sterile due to defect in anther dehiscence and mature pollen grain release at anthesis (PubMed:29915329). Plants silencing YUCCA4 do not exhibit any visible phenotype (PubMed:29915329). Belongs to the FMO family.