Identification and role analysis of an intermediate produced by a polygenic mutant of Monascus pigments cluster in Monascus ruber M7.

Monascus pigments (Mps) are a group of azaphilonic secondary metabolites produced by Monascus spp. via a polyketide pathway. A mutant deleted an about 30 kb region of Mps gene cluster from Monascus ruber M7 was isolated previously, which produces a high amount of a light yellow pigment. The current study revealed that the mutant named ΔMpigJ-R lost proximate eight genes of the Mps gene cluster in M. ruber M7 through genetic analysis at DNA and RNA levels. The produced light yellow material was identified as a benzaldehyde derivative named as 6-(4-hydroxy-2-oxopentyl)-3-methyl-2, 4-dioxocyclohexane carb-aldehyde (M7PKS-1) by FT-IR, NMR, and MS. The sodium acetate-1-(13)C feeding experiment indicated that M7PKS-1 was a product produced from polyketide pathway. Finally, the feeding of M7PKS-1 helped to induce and regain Mps production of the mutants (ΔMpigA and ΔMpigE) which were previously unable to biosynthesize Mps and proved that M7PKS-1 was an initial intermediate of Mps. The results in this study provide a line of action to unveil Monascus pigments biosynthesis pathway.