Role of IscA1 in Low-Frequency Magnetic Field-Associated Changes in Monascus Pigments and Citrinin Levels in Monascus purpureus

We constructed IscA1 overexpression (IscA1+) and RNA interference (RNAi-IscA1) strains to investigate the role of IscA1 in regulating the synthesis of Monascus pigments (MPs) and citrinin (CIT) in Monascus purpureus under low-frequency magnetic field (LF-MF) exposure. Both IscA1+ and RNAi-IscA1 strains exhibited altered nutritional growth and sexual reproduction; however, asexual reproduction, the ultrastructure of spores and mycelia, and biomass in liquid fermentation, remained unaffected. The production of yellow and orange pigments increased in the IscA1+ strain, while the production of red pigments decreased in the RNAi-IscA1 strain. The expression level of the IscA1 was shown to determine intracellular iron ion content in M. purpureus. Exposure to 1.6 mT LF-MF did not impact biomass but significantly enhanced MPs and decreased intracellular iron content on the 6th day of fermentation in both IscA1+ and RNAi-IscA1 strains, while increasing CIT production in the IscA1+ strain. The interplay between IscA1 gene expression and LF-MF exposure jointly regulates the expression of genes related to iron–sulfur cluster assembly, iron homeostasis, and the synthesis of MPs and CIT. These results suggest that LF-MF enhances the expression of the IscA1 gene in M. purpureus, promotes iron–sulfur cluster assembly, regulates intracellular iron distribution, and influences the synthesis of MPs and CIT.