Single and double knockouts of the genes for photosystem I subunits G, K, and H of Arabidopsis. Effects on photosystem I composition, photosynthetic electron flow, and state transitions.
Photosystem I (PSI) of higher plants contains 18 subunits. Using Arabidopsis En insertion lines, we have isolated knockout alleles of the genes psaG, psaH2, and psaK, which code for PSI-G, -H, and -K. In the mutants psak-1 and psag-1.4, complete loss of PSI-K and -G, respectively, was confirmed, whereas the residual H level in psah2-1.4 is due to a second gene encoding PSI-H, psaH1. Double mutants, lacking PSI-G, and also -K, or a fraction of -H, together with the three single mutants were characterized for their growth phenotypes and PSI polypeptide composition. In general, the loss of each subunit has secondary, in some cases additive, effects on the abundance of other PSI polypeptides, such as D, E, H, L, N, and the light-harvesting complex I proteins Lhca2 and 3. In the G-less mutant psag-1.4, the variation in PSI composition suggests that PSI-G stabilizes the PSI-core. Levels of light-harvesting complex I proteins in plants, which lack simultaneously PSI-G and -K, indicate that PSI subunits other than G and K can also bind Lhca2 and 3. In the same single and double mutants, psag-1.4, psak-1, psah2-1.4, psag-1.4/psah2-1.4, and psag-1.4/psak-1 photosynthetic electron flow and excitation energy quenching were analyzed to address the roles of the various subunits in P700 reduction (mediated by PSI-F and -N) and oxidation (PSI-E), and state transitions (PSI-H). Based on the results, we also suggest for PSI-K a role in state transitions.
Varotto
Claudio
C
Zentrum zur Identifikation von Genfunktionen durch Insertionsmutagenese bei Arabidopsis thaliana, Max-Planck-Institut für Züchtungsforschung, Carl-von-Linné Weg 10, 50829 Köln, Germany.
Pesaresi
Paolo
P
Jahns
Peter
P
Lessnick
Angela
A
Tizzano
Marco
M
Schiavon
Fabio
F
Salamini
Francesco
F
Leister
Dario
D
D000483:Alleles; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development; D001483:Base Sequence; D015153:Blotting, Western; D002734:Chlorophyll / Q000378:metabolism; D045342:Light-Harvesting Protein Complexes; D014975:Lutein / Q000378:metabolism; D009154:Mutation; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D045331:Photosystem I Protein Complex; D010860:Pigments, Biological / Q000378:metabolism; D018515:Plant Leaves / Q000235:genetics / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D020524:Thylakoids / Q000378:metabolism; D024341:Xanthophylls / Q000378:metabolism; D065146:Zeaxanthins; D019207:beta Carotene / Q000031:analogs & derivatives* / Q000378:metabolism
D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D010860:Pigments, Biological; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D024341:Xanthophylls; D065146:Zeaxanthins; D019207:beta Carotene; C031140:antheraxanthin; C074493:photosystem I, PSI-K subunit; C074492:photosystem I, PSI-G subunit; D002734:Chlorophyll; C005613:violaxanthin; C001785:chlorophyll P 700; C011947:neoxanthin; D010100:Oxygen; D014975:Lutein