Light-responsive and rhythmic gene expression of psbA2 in cyanobacterium Microcystis aeruginosa K-81

We cloned, sequenced and characterized the psbA2 gene of the cyanobacterium Microcystis aeruginosa K-81 strain. The deduced amino acid sequence of PsbA2 exhibited extensive similarity to the D1 protein, which is known to be a core protein in the reaction center of the photosynthetic Photosystem II in cyanobacteria. The N-terminal amino acid sequence of PsbA2 also showed that this protein is a Form II type of D1 protein, as defined for Synechococcus sp. strain PCC 7942. The psbA2 gene was transcribed as a 1.2kb monocistron, and the potential promoter had an Escherichia coli consensus sequence. The light-responsive psbA2 message exhibited rhythmicity under conditions of constant darkness after prior entrainment to light and dark cycles.