Proteome analysis reveals global response to deletion of mrflbA in Monascus ruber

Monascus spp. are commonly used for a wide variety of applications in the food and pharmaceutical industries. In previous studies, the knock-out of mrflbA (a putative regulator of the G protein α subunit) in M. ruber led to autolysis of the mycelia, decreased pigmentation and lowered mycotoxin production. Therefore, we aimed to obtain a comprehensive overview of the underlying mechanism of mrflbA deletion at the proteome level. A two-dimensional gel electrophoresis analysis of mycelial proteins indicated that the abundance of 178 proteins was altered in the ΔmrflbA strain, 33 of which were identified with high confidence. The identified proteins are involved in a range of activities, including carbohydrate and amino acid metabolism, hyphal development and the oxidative stress response, protein modification, and the regulation of cell signaling. Consistent with these findings, the activity of antioxidative enzymes and chitinase was elevated in the supernatant of the ΔmrflbA strain. Furthermore, deletion of mrflbA resulted in the transcriptional reduction of secondary metabolites (pigment and mycotoxin). In short, the mutant phenotypes induced by the deletion of mrflbA were consistent with changes in the expression levels of associated proteins, providing direct evidence of the regulatory functions mediated by mrflbA in M. ruber.