title: Partially dissecting the steady-state electron fluxes in Photosystem I in wild-type and pgr5 and ndh mutants of Arabidopsis.
abstract: Cyclic electron flux (CEF) around Photosystem I (PS I) is difficult to quantify. We obtained the linear electron flux (LEFO2) through both photosystems and the total electron flux through PS I (ETR1) in Arabidopsis in CO2-enriched air. ΔFlux = ETR1 - LEFO2 is an upper estimate of CEF, which consists of two components, an antimycin A-sensitive, PGR5 (proton gradient regulation 5 protein)-dependent component and an insensitive component facilitated by a chloroplastic nicotinamide adenine dinucleotide dehydrogenase-like complex (NDH). Using wild type as well as pgr5 and ndh mutants, we observed that (1) 40% of the absorbed light was partitioned to PS I; (2) at high irradiance a substantial antimycin A-sensitive CEF occurred in the wild type and the ndh mutant; (3) at low irradiance a sizable antimycin A-sensitive CEF occurred in the wild type but not in the ndh mutant, suggesting an enhancing effect of NDH in low light; and (4) in the pgr5 mutant, and the wild type and ndh mutant treated with antimycin A, a residual ΔFlux existed at high irradiance, attributable to charge recombination and/or pseudo-cyclic electron flow. Therefore, in low-light-acclimated plants exposed to high light, ΔFlux has contributions from various paths of electron flow through PS I.
authors.affiliation: College of Animal Science and Technology, Northwest A&F University Yangling, China ; Division of Plant Sciences, Research School of Biology, The Australian National University Canberra, ACT, Australia.
authors.forename: Jiancun
authors.initials: J
authors.lastname: Kou
authors.affiliation: Division of Plant Sciences, Research School of Biology, The Australian National University Canberra, ACT, Australia.
authors.forename: Shunichi
authors.initials: S
authors.lastname: Takahashi
authors.affiliation: Division of Plant Sciences, Research School of Biology, The Australian National University Canberra, ACT, Australia ; State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, The Chinese Academy of Sciences Beijing, China.
authors.forename: Da-Yong
authors.initials: DY
authors.lastname: Fan
authors.affiliation: Division of Plant Sciences, Research School of Biology, The Australian National University Canberra, ACT, Australia.
authors.forename: Murray R
authors.initials: MR
authors.lastname: Badger
authors.affiliation: Division of Plant Sciences, Research School of Biology, The Australian National University Canberra, ACT, Australia.
authors.forename: Wah S
authors.initials: WS
authors.lastname: Chow
keywords: Arabidopsis; P700; antimycin A; cyclic electron flow; ndh mutant; pgr5 mutant; photosystem I