Abstract
It is not clear at the molecular level how cyanobacteria acclimate the photosynthetic antenna, phycobilisomes, to variable light conditions. Recently we showed that in Synechocystis the transcript level of a rod-core linker gene, cpcG2, was regulated by a unique two-component system comprising a phytochrome-like histidine kinase and OmpR-type response regulator. Synechocystis has two paralogous cpcG genes (cpcG1 and cpcG2) in the genome. We created their disruptants, and analyzed assembly of the phycobilisome through sucrose density gradient ultracentrifugation. We found that the phycobilisome in the cpcG2 mutant almost fully assembled, while in the cpcG1 mutant phycobiliproteins partially assembled to form several subcomplexes. In the double mutant assembly was more suppressed than in the single cpcG1 mutant. These results suggest that CpcG2 plays an auxiliary but regulatory role in the assembly of phycobilisome. Further investigation will be done to elucidate the role of CpcG2 in acclimation to light conditions.
