The <i>Fg</i>Not3 Subunit of the Ccr4-Not Complex Regulates Vegetative Growth, Sporulation, and Virulence in <i>Fusarium graminearum</i>

The Ccr4-Not complex is evolutionarily conserved and important for multiple cellular functions in eukaryotic cells. In this study, the biological roles of the FgNot3 subunit of this complex were investigated in the plant pathogenic fungus Fusarium graminearum. Deletion of FgNOT3 resulted in retarded vegetative growth, retarded spore germination, swollen hyphae, and hyper-branching. The ΔFgnot3 mutants also showed impaired sexual and asexual sporulation, decreased virulence, and reduced expression of genes related to conidiogenesis. Fgnot3 deletion mutants were sensitive to thermal stress, whereas NOT3 orthologs in other model eukaryotes are known to be required for cell wall integrity. We found that FgNot3 functions as a negative regulator of the production of secondary metabolites, including trichothecenes and zearalenone. Further functional characterization of other components of the Not module of the Ccr4-Not complex demonstrated that the module is conserved. Each subunit primarily functions within the context of a complex and might have distinct roles outside of the complex in F. graminearum. This is the first study to functionally characterize the Not module in filamentous fungi and provides novel insights into signal transduction pathways in fungal development.Ccr4-Not复合物（Ccr4-Not complex）在进化上具有保守性，对真核细胞的多种细胞功能至关重要。本研究以植物病原真菌禾谷镰孢菌（Fusarium graminearum）为对象，探究了该复合物的FgNot3亚基的生物学功能。敲除FgNOT3基因会导致菌株营养生长迟缓、孢子萌发受阻、菌丝肿胀以及过度分枝。ΔFgnot3突变体还表现出有性与无性产孢能力受损、致病力下降，以及产孢相关基因表达量降低的表型。Fgnot3基因敲除突变体对热胁迫敏感，而已有研究证实，其他模式真核生物中的NOT3同源基因对维持细胞壁完整性必不可少。本研究发现，FgNot3可作为次级代谢产物合成的负调控因子，这类产物包括单端孢霉烯族毒素（trichothecenes）与玉米赤霉烯酮（zearalenone）。对Ccr4-Not复合物的Not模块其他组分的进一步功能表征显示，该模块具有进化保守性。在禾谷镰孢菌中，每个亚基主要以复合物的形式发挥功能，同时也可能在复合物之外承担独特的生物学作用。本研究是首次在丝状真菌中对Not模块进行功能表征的工作，为真菌发育过程中的信号转导通路研究提供了全新的见解。