Abstract
In certain cyanobacteria, green-light irradiation induces accumulation of a green-absorbing pigment, phycoerythrin, whereas red-light irradiation induces accumulation of a red-absorbing pigment, phycocyanin, in the photosynthetic light-harvesting phycobilisome. We have shown that genes of a cyanobacteriochrome and a transcription factor (ccaS and ccaR) are essential for expression of phycobilisome linker gene in Synechocystis sp. PCC 6803, which does not possess phycoerythrin (Katayama et al 2004, PCP 45, S124). We recently demonstrated the green/red reversible photoconversion of CcaS and its light-regulated phosphotransfer to CcaR (Hirose et al., 2008, PNAS 105, 9528-9533). Here, we generated mutants of ccaS and ccaR in Nostoc punctiforme ATCC 29133 that accumulates phycoerythrin under green light but not phycocyanin under red light (group II chromatic adaptation). Under green or red light, phycoerythrin contents were lower in both mutants than wild type. We will discuss the mechanism how CcaS and CcaR regulate green light-induced phycoerythrin accumulation in Nostoc.
