VdOMO contributes to development, stress adaptation, siderophore-associated iron acquisition, and early host...

Verticillium dahliae is a soilborne fungal pathogen that causes Verticillium wilt in cotton and many other crops. While siderophore-associated iron acquisition is recognized as crucial, its precise connections to fungal development, stress adaptation, and host colonization remain incompletely elucidated. This study identifies the VdOMO protein as a putative SidA-family L-ornithine N5-monooxygenase through phylogenetic and pairwise sequence analyses. Analyses of independent deletion mutants and a complemented strain showed that VdOMO contributes to conidial morphology and production, microsclerotium formation, and melanization, growth on selected carbon sources, cell wall integrity, and adaptation to alkaline, salt, and oxidative stresses. Although final visible disease symptoms were comparable among inoculated groups, ΔVdOMO mutants exhibited reduced vascular browning, diminished fungal biomass accumulation at early infection stages, and impaired cellophane penetration. A representative ΔVdOMO mutant also displayed decreased biomass-normalized extracellular chrome azurol S (CAS)-reactive iron-chelating activity and intracellular iron accumulation, both of which were restored to wild-type levels upon complementation. Furthermore, VdOMO deletion was linked to iron-condition-dependent alterations in the expression of genes involved in iron regulation, siderophore biosynthesis, and siderophore transport. Collectively, these findings underscore a significant role for VdOMO in siderophore-associated iron acquisition, fungal development, stress adaptation, and the early stages of host colonization in V. dahliae.