XdhR negatively regulates actinorhodin biosynthesis in Streptomyces coelicolor M145

The xdhR gene encodes a TetR-family regulator in Streptomyces coelicolor. However, little is known about the function of XdhR in regulating actinorhodin production. Here, we report that XdhR negatively regulates actinorhodin biosynthesis in S. coelicolor. Deletion of xdhR resulted in overproduction of actinorhodin by approximately 2.5-fold compared to the wild-type strain. Complementation of the xdhR deletion strain restored actinorhodin production to normal levels. In addition, the relative expression levels of actinorhodin cluster genes were all significantly increased in the xdhR deletion strain compared to the wild-type strain. XdhR can specifically bind the promoters of actII-4 and actII-1, two pathway-specific regulators of actinorhodin biosynthesis. These results suggest that xdhR negatively controls actinorhodin biosynthesis by directly regulating actII-4 and actII-1 in S. coelicolor.