title: A qualitative analysis of the regulation of cyclic electron flow around photosystem I from the post-illumination chlorophyll fluorescence transient in Arabidopsis: a new platform for the in vivo investigation of the chloroplast redox state.
abstract: A transient in chlorophyll fluorescence after cessation of actinic light illumination, which has been ascribed to electron donation from stromal reductants to plastoquinone (PQ) by the NAD(P)H-dehydrogenase (NDH) complex, was investigated in Arabidopsis thaliana. The transient was absent in air in a mutant lacking the NDH complex (ndhM). However, in ndhM, the transient was detected in CO(2)-free air containing 2% O(2). To investigate the reason, ndhM was crossed with a pgr5 mutant impaired in ferredoxin (Fd)-dependent electron donation from NADPH to PQ, which is known to be redundant for NDH-dependent PQ reduction in the cyclic electron flow around photosystem I (PSI). In ndhM pgr5, the transient was absent even in CO(2)-free air with 2% O(2), demonstrating that the post-illumination transient can also be induced by the Fd- (or PGR5)-dependent PQ reduction. On the other hand, the transient increase in chlorophyll fluorescence was found to be enhanced in normal air in a mutant impaired in plastid fructose-1,6-bisphosphate aldolase (FBA) activity. The mutant, termed fba3-1, offers unique opportunities to examine the relative contribution of the two paths, i.e., the NDH- and Fd- (or PGR5)-dependent paths, on the PSI cyclic electron flow. Crossing fba3-1 with either ndhM or pgr5 and assessing the transient suggested that the main route for the PSI cyclic electron flow shifts from the NDH-dependent path to the Fd-dependent path in response to sink limitation of linear electron flow.
authors.affiliation: Department of Agriculture, Kyushu University, Fukuoka, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Gotoh
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Matsumoto
authors.forename: Ken'ichi
authors.initials: K
authors.lastname: Ogawa
authors.forename: Yoshichika
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Michito
authors.initials: M
authors.lastname: Tsuyama
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000378:metabolism* / Q000528:radiation effects*; D002734:Chlorophyll / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism* / Q000528:radiation effects*; D004579:Electron Transport / Q000528:radiation effects; D005288:Ferredoxins / Q000378:metabolism; D005453:Fluorescence; D005634:Fructose-Bisphosphate Aldolase / Q000037:antagonists & inhibitors / Q000378:metabolism; D015151:Immunoblotting; D008027:Light; D009154:Mutation / Q000235:genetics; D009252:NADPH Dehydrogenase / Q000378:metabolism; D010084:Oxidation-Reduction / Q000528:radiation effects; D045331:Photosystem I Protein Complex / Q000378:metabolism*; D010971:Plastoquinone / Q000378:metabolism
chemical_list: D005288:Ferredoxins; D045331:Photosystem I Protein Complex; D002734:Chlorophyll; D009252:NADPH Dehydrogenase; D005634:Fructose-Bisphosphate Aldolase; D010971:Plastoquinone