Deletion of pigR gene in Monascus ruber leads to loss of pigment production

Pigments produced by Monascus are traditional food colorants and are widely used as dietary supplements. Since genes involving in pigment biosynthesis have not been reported, we describe the identification of a putative pigment-regulatory gene (pigR) obtained by molecular analysis of an albino strain of Monascus ruber M7. In the pigR-deleted strain (Delta pigR), neither the pigments nor pigR expression were detected by HPLC or reverse-transcription PCR, respectively, whereas the introduction of the pigR, together with a constitutive trpC promoter into Delta pigR, caused it to produce 5.4 U of red pigments/g dry mycelia, about 12-fold higher than Monascus ruber M7 (0.46 U/g dry mycelia). Thus pigR up-regulates pigment production in Monascus ruber M7.