A dim-light trans-acting activator of Puf and Puh expression, that has no effect on the expression of the Puc operon. Responsible for regulating light-harvesting-I and reaction center structural gene expression differentially from that of light-harvesting-II expression in response to alterations in light. Proper light regulation of light-harvesting and reaction center polypeptide synthesis is an important physiological trait that enables cells to adapt to ever-changing environmental conditions of light intensity. Homodimer that oligomerizes on DNA into higher-order complexes that form bridges between disparate regions of DNA compacting it (By similarity). Expressed in light-grown cells, probably a member of the senC-regA-hvrA operon (PubMed:7961455). Grows normally under saturating light (6000 lux), in low light (80 lux) grows poorly, decreased induction of puf and puh but not puc operons nor genes for bacteriochlorophyll biosynthesis (PubMed:7961455). Belongs to the histone-like protein H-NS family.