mrvam7, a conserved SNARE gene involved in vacuolar fusion, is required for development and secondary metabolism in Monascus ruber M7

Vam7 (vacuolar morphogenesis 7), a Qc-soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) that mediates vacuolar fusion, is involved in vacuolar morphogenesis, vegetative growth, sexual and asexual reproduction, and compartmentalized biosynthesis of secondary metabolites in various filamentous fungi. In this study, the homolog of vam7 gene, mrvam7, in Monascus ruber M7 was functionally characterized through gene modification and transcriptome analysis. The results showed that the mrvam7 complementation and overexpression strains exhibited phenotypic similarities to M. ruber M7, whereas the mrvam7 null strain exhibited fragmented vacuoles, slowed growth and diminished sexual and asexual sporulation. Furthermore, the mrvam7 knockout strain displayed a notable increase in citrinin production alongside a significant decrease in Monascus pigments production. Transcriptome data revealed that the deletion of mrvam7 altered the expression levels of several genes involved in sexual and asexual reproduction, carbon and nitrogen source utilization, and secondary metabolites biosynthetic gene clusters. Collectively, these findings underscore the critical role of mrvam7-mediated vacuolar fusion in growth, development, and the compartmentalized biosynthesis and distribution of secondary metabolites in M ruber M7. This study provides novel insights into the mechanisms underlying of compartmentalized secondary metabolites biosynthesis in Monascus species. •The deletion of mrvam7 leads to vacuoles fragmentation.•mrvam7 is necessary for carbon and nitrogen sources utilization.•Vacuole is involved in the compartmentalized biosynthesis of citrinin and Monascus pigments.