Abstract
Light reactions of photosynthetic consist of linear and photosystem I (PSI) cyclic electron transport. The light reactions have been generally explained by linear electron transport, and the physiological function of PSI cyclic electron transport was unknown for a long time. 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 NAD(P)H dehydrogenase (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 transformed with the Pinus thunbergii PGR5 gene showed Antimycin A-resistance. We also determined the amino acid that determines the resistance. The results suggest that Antimycin-A binds to PGR5 or protein closely localized to PGR5 in thylakoids.
