Lack of the small plastid-encoded PsbJ polypeptide results in a defective water-splitting apparatus of photosystem II, reduced photosystem I levels, and hypersensitivity to light.
Photosystem II is a large pigment-protein complex catalyzing water oxidation and initiating electron transfer processes across the thylakoid membrane. In addition to large protein subunits, many of which bind redox cofactors, photosystem II particles contain a number of low molecular weight polypeptides whose function is only poorly defined. Here we have investigated the function of one of the smallest polypeptides in photosystem II, PsbJ. Using a reverse genetics approach, we have inactivated the psbJ gene in the tobacco chloroplast genome. We show that, although the PsbJ polypeptide is not principally required for functional photosynthetic electron transport, plants lacking PsbJ are unable to grow photoautotrophically. We provide evidence that this is due to the accumulation of incompletely assembled water-splitting complexes, which in turn causes drastically reduced photosynthetic performance and extreme hypersensitivity to light. Our results suggest a role of PsbJ for the stable assembly of the water-splitting complex of photosystem II and, in addition, support a control of photosystem I accumulation through photosystem II activity.
Hager
Martin
M
Institut für Biologie III, Universität Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany.
Hermann
Marita
M
Biehler
Klaus
K
Krieger-Liszkay
Anja
A
Bock
Ralph
R
D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D015152:Blotting, Northern; D015139:Blotting, Southern; D002736:Chloroplasts / Q000378:metabolism; D015536:Down-Regulation; D004591:Electrophoresis, Polyacrylamide Gel; D017343:Genes, Plant; D008040:Genetic Linkage; D015151:Immunoblotting; D008027:Light; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism; D010455:Peptides / Q000737:chemistry; D010641:Phenotype; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism*; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D018521:Plant Physiological Phenomena; D030821:Plants, Genetically Modified; D018087:Plastids / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013050:Spectrometry, Fluorescence; D020524:Thylakoids / Q000378:metabolism; D013997:Time Factors; D014026:Nicotiana / Q000235:genetics; D014867:Water / Q000737:chemistry*
D001426:Bacterial Proteins; D008565:Membrane Proteins; D010455:Peptides; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; C079258:psbJ protein, Synechocystis; D014867:Water; D010100:Oxygen