Abstract
Light reactions of photosynthesis consist of linear and photosystem I (PSI) cyclic electron transport. Recently, it was clarified that linear electron transport cannot supply enough ATP required for CO2 fixation and extra ATP is produced by PSI cyclic electron transport. In higher plants PSI cyclic electron transport consists of two pathways. The main route depends on PGR5 protein, while chloroplast NDH is involved in the minor pathway. The PGR5-dependent pathway is sensitive Antimycin A, but its target is still unclear. We discovered that Arabidopsis thaliana transformed with the Pinus thunbergii PGR5 gene was resistant to Antimycin A. Eight amino acids are different between At and Pt PGR5 and all the single amino acid alterations were introduced to At and Pt PGR5. We clarified one amino acid alteration is sufficient to confer the Antimycin A resistance. The results suggest that Antimycin A binds to PGR5 or the protein closely localized to PGR5 in thylakoids. This is the evidence suggesting the directly link of PGR5-dependent PSI cyclic pathway and Antimycin A sensitive pathway.
