A contribution to molecular ecology; Clarifying the significance of orf62 gene in cyanobacterium Synechocystis PCC 6803

Abstract

Open reading frame 62 (orf62) encodes a hydrophobic protein with 62 amino acid residues. Hydrophobicity analysis of the protein points to two membrane-spanning re-ions. Proteins homologous to the orf62 gene product of Synechocystis PCC6803 are found e.g. in the plastid genomes of all organisms examined so far. All known orf62 sequences show high degree of similarity to each other. In this study our aim is to reveal the cellular role of orf62 in the widely used model organism Synechocystis PCC6803. For this purpose, a deletion mutant as well as an inactivation mutant of orf62 was constructed. The polypeptide content of the thylakoid membranes and the transcripts of some photosynthetic genes of the mutants compared to wild type, were analyzed by Western and Northern blotting. The results showed that amounts of the photosynthetic polypeptides and transcripts are unaltered in mutants. The respiration and the oxygen evolution rates were higher in mutants where the growth rate was generally lower than in wild type. According to these results it can be concluded that, orf62 might be a regulatory gene which controls electron flow in photosynthetic chain.