Characterization of key upstream asexual developmental regulators in Monascus ruber M7

Monascus species are traditional edible and medicinal filamentous fungi with a very long history in East Asia, but their sparse production of asexual spores (conidia) limits their large-scale industrial application. Previous studies have revealed that the flbA ortholog plays a negative role in the conidiation of Monascus ruber M7. FlbA, together with FlbB, FlbC, FlbD, FlbE, and FluG, were shown to be upstream development activators (UDAs) in the asexual development pathway in the model fungus Aspergillus nidulans. In the present study, homologs of these UDAs in M. ruber M7 were identified and functionally characterized. Disruption of MrflbB, MrflbD, and MrflbE delayed and decreased conidiation in M7, whereas the deletion of MrflbC or MrfluG resulted in no detectable change in sporulation. Deletion of MrflbA not only increased conidial number but also postponed sexual development in M7. Furthermore, the deletion of some UDAs also affected the production of secondary metabolites, particularly citrinin, whose yields were dramatically decreased in the Delta MrflbC and Delta MrflbA mutants. These findings provide new insights and opportunities to further explore the asexual development mechanism and modify the conidial production in Monascus spp.

Automated summary

Monascus species are traditional filamentous fungi in East Asia, but their low production of asexual spores limits their industrial application. In this study, the researchers identified and characterized the genes involved in asexual development and secondary metabolite production in Monascus ruber M7. The deletion of certain genes affected conidiation and secondary metabolite yields. These findings provide new insights and opportunities for improving conidial production in Monascus spp.