Coat Proteins of the Novel Victoriviruses FaVV1 and FaVV2 Suppress Sexual Reproduction and Virulence in the Pathogen of Fusarium Head Blight

Fusarium head blight (FHB), a disease inflicted by <i>Fusarium graminearum</i> and <i>F. asiaticum</i>, poses a growing threat to wheat in China, particularly in the face of climate change and evolving agricultural practices. This study unveiled the discovery of the victorivirus FgVV2 from the <i>F. asiaticum</i> strain F16176 and comprehensively characterized the function of the two victoriviruses FaVV1 and FaVV2 in virulence. Through comparative analysis with a virus-free strain, we established that these mycoviruses markedly repress the sexual reproduction and pathogenicity of their fungal hosts. Furthermore, we synthesized the coat protein (CP) genes <i>CP1</i> from FaVV1 and <i>CP2</i> from FaVV2, which were fused with the green fluorescent protein (GFP) gene and successfully expressed in <i>Fusarium</i> strains in wild-type isolates of <i>F. asiaticum</i> and <i>F. graminearum</i>. Similar to virus-infected strains, the transformed strains expressing CPs showed a significant decrease in perithecia formation and pathogenicity. Notably, CP2 exhibited a stronger inhibitory effect than CP1, yet the suppression of sexual reproduction in <i>F. graminearum</i> was less pronounced than that in <i>F. asiaticum</i>. Additionally, the pathogenicity of the <i>F. asiaticum</i> and <i>F. graminearum</i> strains expressing CP1 or CP2 was substantially diminished against wheat heads. The GFP-tagged CP1 and CP2 revealed distinct cellular localization patterns, suggesting various mechanisms of interaction with the host. The findings of this study provide a significant research foundation for the study of the interaction mechanisms between FaVV1 and FaVV2 with their hosts, as well as for the exploration and utilization of fungal viral resources.