MrflbA, Encoding a Putative FlbA, is Involved in Aerial Hyphal Development and Secondary Metabolite Production in Monascus Ruber M-7

FlbA (fluffy low brlA expression), a regulator of the G protein signalling (RGS) pathway, has been implicated in the control of hyphal development, sporulation, mycotoxin/pigment production in many kinds of filamentous fungi and yeasts. In the current study, a FlbA-like protein gene mrflbA (Monascus ruber flbA) was isolated, sequenced, and disrupted in order to investigate the RGS function in M. ruber. The results revealed that the derived protein of the mrflbA gene consisted of 734 amino acids and had the conserved RGS domain at the C-terminus and two DEP (dishevelled, Egl-10, pleckstrin) domains at the N-terminus similar to the structure of RGS proteins in other filamentous fungi. Deletion of the mrflbA gene resulted in the formation of an abnormal colony phenotype with fluffy aerial hyphae that autolyzed as the colony grew on potato dextrose agar (PDA) at 28°C. Additionally, mrflbA deletion could repress conidial germination and pigment/citrinin production in M. ruber M-7. Real-time RT-PCR analysis demonstrated that the transcription level of the G protein α subunit (Gα) was remarkably increased in the mrflbA deletion strain. These results suggest that mrflbA is involved in the modulation of aerial hyphal development and secondary metabolism, as well as, negative regulation of Gα subunit expression in M. ruber M-7.