Abstract:

Flavin monooxygenases (FMOs) are a class of flavin adenine dinucleotide (FAD)-dependent oxidoreductases that catalyze the oxidation of diverse substrates and play vital roles in plant metabolic regulation and environmental adaptation. The plant FMOs superfamily comprises multiple functional subfamilies, among which FMO1, YUCCAs, and FMOGS-OXs are most representative, functioning in immune defense, auxin biosynthesis, secondary metabolism, and stress responses. This review summarizes the structural features, evolutionary diversification, and functional mechanisms of these three subfamilies, and highlights recent advances in their roles in plant growth, development, and stress adaptation. FMOs generally contain conserved FAD/NADPH-binding domains and have undergone gene expansion during evolution, conferring functional diversification as well as pronounced redundancy and pleiotropy. Nevertheless, the natural substrate spectrum of most FMOs remains unresolved, and the molecular mechanisms driving their gene expansion and evolutionary diversification are yet to be elucidated. Moreover, their spatiotemporal specificity together with functional redundancy severely constrains in-depth mechanistic and applied research. Considering future, the integration of metabolomics, spatial omics, and artificial intelligence is expected to open new avenues for functional characterization and translational applications of FMOs, providing promising targets for molecular design breeding aimed at enhancing crop stress tolerance and yield improvement.

Key words: FMOs, gene family, functional diversity, growth and development, stress resistance