Activates transcription. Positively regulates PcrtB promoter upstream of the crtB operon in a cAMP-independent manner. Regulated genes include genes encoding DNA photolyase, phytoene synthase and cytochrome P450 monooxygenase, which are involved in carotenoid biosynthesis (PubMed:21421762). Positively regulates the light-inducible gene cluster in the megaplasmid in a cAMP-independent manner (PubMed:25294106). No production of carotenoids in dark or light conditions (PubMed:21421762). Does not activate expression of TT_P0044, TT_P0049 or TT_P0070 in dark or light conditions (PubMed:25294106).