Effects of blue light on pigment and citrinin production in Monascus ruber M7 via MrcreD, encoding an arrestin-like protein.

Blue light, as an important environmental factor, greatly affects the production of Monascus pigments (MPs) and citrinin in Monascus spp. In this study, the deletion, complementation, and overexpression mutants of MrcreD from Monascus ruber M7, which encodes an arrestin-like protein, were constructed and cultivated on PDA (Potato dextrose agar) medium to study the effects of blue light on MPs and citrinin production. The results revealed that blue light inhibited the formation of cleistothecia, conidia, and the production of MPs and citrinin in M. ruber M7. However, under blue light, in contrast to M. ruber M7, MrcreD-overexpressing strain displayed increased production of extracellular yellow pigments and intracellular orange pigments, whereas MrcreD-deleted strain showed enhanced production of intracellular yellow and orange pigments. Then, the extracellular citrinin production decreased in both mutants. The RT-qPCR results demonstrated that compared to M. ruber M7, overexpressing MrcreD increased the expression of genes involved in MPs biosynthesis, and decreased the genes involved in citrinin biosynthesis, while deleting MrcreD increased the expression of citrinin-relative genes. This is the first time that the functions of MrcreD gene in filamentous fungi have been researched under blue light, and it provides a strategy for exploring complex light-regulatory systems in filamentous fungi.