Deletion of the tobacco plastid psbA gene triggers an upregulation of the thylakoid-associated NAD(P)H dehydrogenase complex and the plastid terminal oxidase (PTOX).
We have constructed a tobacco psbA gene deletion mutant that is devoid of photosystem II (PSII) complex. Analysis of thylakoid membranes revealed comparable amounts, on a chlorophyll basis, of photosystem I (PSI), the cytochrome b6f complex and the PSII light-harvesting complex (LHCII) antenna proteins in wild-type (WT) and DeltapsbA leaves. Lack of PSII in the mutant, however, resulted in over 10-fold higher relative amounts of the thylakoid-associated plastid terminal oxidase (PTOX) and the NAD(P)H dehydrogenase (NDH) complex. Increased amounts of Ndh polypeptides were accompanied with a more than fourfold enhancement of NDH activity in the mutant thylakoids, as revealed by in-gel NADH dehydrogenase measurements. NADH also had a specific stimulating effect on P700+ re-reduction in the DeltapsbA thylakoids. Altogether, our results suggest that enhancement of electron flow via the NDH complex and possibly other alternative electron transport routes partly compensates for the loss of PSII function in the DeltapsbA mutant. As mRNA levels were comparable in WT and DeltapsbA plants, upregulation of the alternative electron transport pathways (NDH complex and PTOX) occurs apparently by translational or post-translational mechanisms.
Baena-González
Elena
E
Department of Biology, Plant Physiology and Molecular Biology, University of Turku, FIN-20014 Turku, Finland.
Allahverdiyeva
Yagut
Y
Svab
Zora
Z
Maliga
Pal
P
Josse
Eve-Marie
EM
Kuntz
Marcel
M
Mäenpää
Pirkko
P
Aro
Eva-Mari
EM
D038181:FMN Reductase / Q000235:genetics*; D017353:Gene Deletion; D009097:Multienzyme Complexes / Q000235:genetics; D016296:Mutagenesis; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000235:genetics*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism; D018515:Plant Leaves / Q000201:enzymology / Q000648:ultrastructure; D010940:Plant Proteins / Q000235:genetics; D018087:Plastids / Q000201:enzymology / Q000235:genetics* / Q000648:ultrastructure; D015183:Restriction Mapping; D020524:Thylakoids / Q000201:enzymology / Q000235:genetics; D014026:Nicotiana / Q000201:enzymology / Q000235:genetics*; D014158:Transcription, Genetic
D009097:Multienzyme Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D010940:Plant Proteins; D010088:Oxidoreductases; D038181:FMN Reductase