The Sirtuin Family FvSIRT5 and FvSIR2 Are Important for Fumonisin B Biosynthesis and Conidiation in Fusarium verticillioides

In filamentous fungi, the modification of histone acetylation and deacetylation is crucial for the regulation of secondary metabolism and pathogenicity. So far, there has been no functional study on histone deacetylases (HDACs) in Fusarium verticillioides, a causal agent of destructive diseases of maize. Herein, we identified and characterized the HDACs FvSIRT5 and FvSIR2 in F. verticillioides. The results showed that the disruption of FvSIRT5 and FvSIR2 lead to increased and morphologically abnormal conidia and, consequently, high expression levels of conidiation-specific genes. Deletion of FvSIRT5 and FvSIR2 also affected autophagy, which may have resulted in the defects of conidial and hyphal viability. Fumonisin B production was significantly reduced in the Δsirt5 and Δsir2 mutants, and the expression of genes (FUMs and PKSs) involved in secondary metabolism was also significantly downregulated. Notably, FvSIRT5 and FvSIR2 may be involved in histone acetylation at H3K9, H3K14, H3K27, and H4K16 residues, which has never been reported in fungi. Interestingly, FvSIRT5 and FvSIR2 interact with ORC1 (origin recognition complex subunit 1) and some alternative splice forms of FUM21 (fumonisin biosynthetic transcription factor). Moreover, mutations of FvSIRT5 and FvSIR2 are dispensable for virulence in F. verticillioides. Taken together, these results suggest that FvSIRT5 and FvSIR2 are important for histone H3 and H4 acetylation and further for transcriptional regulation of genes related to conidiation and secondary metabolism in F. verticillioides.