MpigE, a gene involved in pigment biosynthesis in Monascus ruber M7

Monascus pigments (MPs) have been used as food colorants for several centuries in Asian countries. However, MP biosynthesis pathway is still a controversy, and only few related genes have been reported. In this study, the function of MpigE, a gene involved in MP biosynthesis in Monascus ruber M7, was analyzed. The results revealed that the disruption, complementation, and overexpression of MpigE in M. ruber M7 had very little effects on the growth and phenotypes except MPs. The MpigE deletion strain (a dagger MpigE) just yielded four kinds of yellow MPs and very little red pigments, while the wild-type strain M. ruber M7 produced a MP complex mixture including three (orange, red, and yellow) categories of MP compounds. Two of the four yellow MPs produced by a dagger MpigE were the same as those yielded by M. ruber M7. The MpigE complementation strain (a dagger MpigE::MpigE) recovered the ability to generate orange and red MPs as M. ruber M7. The MP types produced by the MpigE overexpression strain (M7::PtrpC-MpigE) were consistent with those of M. ruber M7, while the color value was about 1.3-fold as that of M. ruber M7 (3,129 U/g red kojic). For the production of citrinin, the disruption of MpigE almost had no influence on the strain, whereas the overexpression of MpigE made citrinin decrease drastically in YES fermentation. This work will make a contribution to the study on the biosynthesis pathway of MPs in M. ruber.