Work

Molecular and Biological Characterization of Novel Mitovirus Infecting Phytopathogenic Fungus Ustilaginoidea virens

Year: 2024

Type: article

Abstract: Rice false smut (RFS), caused by the ascomycete fungus Ustilaginoidea virens (Cooke) Takahashi, is a notable panicle disease of rice. Mycoviruses represent a category of viruses capable of infecting various fungal groups , garnering interest for their potential application in the biological control of plant fungal diseases . We identified a novel positive-sense single-stranded RNA virus, named Ustilaginoidea virens mitovirus 1 (UvMV1), from an abnormal U. virens strain Uv488. The complete genome sequence of UvMV1 is 2 474 nt in length and contains a large open reading frame encoding RNA-dependent RNA polymerase. UvMV1 is classified as a new member of the genus Unuamitovirus in the family Mitoviridae based on phylogenetic analysis . It is effectively transmitted vertically through conidia of strain Uv488 and horizontally through hyphal fusion between vegetatively compatible individuals with an 80% transmission efficiency. We further demonstrated that UvMV1 significantly influenced conidiation , colony morphology, growth rate, secondary metabolite production, and the response to environmental stress in U. virens . Furthermore, qRT-PCR results aimed at detecting the expression levels of autophagy-related genes suggested that UvMV1 infection had the potential to induce autophagy in U. virens . Activation or inhibition of autophagy through chemical experiments demonstrated that UvMV1 enhances viral titers by inducing autophagy in U. virens , while inhibition of autophagy results in decreased UvMV1 titers. Transcriptome analyses consistently demonstrated that UvMV1 regulated the expression of genes associated with secondary metabolism, mycelial growth , virulence, and the mitogen-activated protein kinase signaling pathway , thereby influencing both the antiviral response and the virulence of U. virens . The data presented collectively identified a novel mycovirus responsible for inducing growth abnormalities in U. virens , and elucidated the regulatory mechanisms during mycovirus-host fungus interactions, particularly the autophagy pathway. These findings offer new perspectives and potential control strategies for managing RFS in agricultural settings.

Source: Rice Science

DOI: 10.1016/j.rsci.2024.11.002