A DUF3455 domain‐containing protein promotes <i>Ustilaginoidea virens</i> infection and functions as a plant immune elicitor

Abstract Rice false smut (RFS), caused by Ustilaginoidea virens , poses a serious threat to global rice production by forming false smut balls and reducing grain yield and quality. Although numerous putative effectors have been predicted in the U. virens genome, only a limited number have been functionally characterized. Here, we identify and characterize U. virens DUF domain‐containing protein 1 (UvDUF1), a secreted, ascomycete‐conserved protein harboring a DUF3455 domain. UvDUF1 is strongly induced during the early stages of infection, and its deletion significantly reduces the virulence of U. virens . Pathogenicity is restored by complementation with the wild‐type UvDUF1 gene but not with a signal peptide‐deficient variant, demonstrating that secretion is indispensable for its virulence function. Recombinant UvDUF1 elicits early immune responses, including reactive oxygen species bursts and activation of defense‐related genes, and enhances rice resistance to Magnaporthe oryzae . Moreover, UvDUF1 induces immune responses in the nonhost Nicotiana benthamiana and increases resistance to Phytophthora species. Collectively, results show that UvDUF1 contributes to pathogen virulence and plant immunity induction, providing new avenues for the development of environmentally friendly strategies for crop disease management.