Mutational analysis of MpPhy reveals magnetoreception and photosensitivity involvement in secondary metabolites biosynthesis in Monascus purpureus.

Light or low frequency magnetic field (LF-MF) as one of the cultivation environments affects secondary metabolites (SMs) production of M. purpureus. Phytochrome (Phy) is a hybrid histidine kinase possessing dual properties of photoreceptor and kinase to sense red and far-red light. The interaction effects of LF-MF and light on SMs of M. purpureus was investigated by knocking out the Phy-like gene in M. purpureus (MpPhy) by homologous recombination. A MpPhy-deletion (ΔMpPhy) strain produced less Monascus pigments (MPs) and monacolin K (mon K) than the wild-type (WT) strain and reduced citrinin production by 78.3% on 10th day but didn't affect the biomass. These results indicated that the MpPhy gene is involved in SMs biosynthesis of M. purpureus. MPs production in WT was decreased significantly when the inoculum was exposed to white/blue/green/red light (500 Lux). But it in ΔMpPhy was no significant difference when exposed to white/red light. The colony size of ΔMpPhy was smaller on potato dextrose agar media containing 0.01% SDS. These results indicated that the deletion of MpPhy gene affected the aerial hyphae and increased sensitivity to cell membrane stress but decreased sensitivity to red light. The inoculum of both WT and ΔMpPhy was exposure to the LF-MF (50 Hz). The accumulation of WT secondary metabolites was not changed, while SMs production of ΔMpPhy was significantly enhanced under exposed to 2.0 mT LF-MF. This indicated that the decrease of SMs caused by the deletion of MpPhy gene was restored by LF-MF. It revealed that there is a crosstalk between magnetoreception and photosensitivity.