Evidence for a role of VIPP1 in the structural organization of the photosynthetic apparatus in Chlamydomonas.
The vesicle-inducing protein in plastids (VIPP1) was suggested to play a role in thylakoid membrane formation via membrane vesicles. As this functional assignment is under debate, we investigated the function of VIPP1 in Chlamydomonas reinhardtii. Using immunofluorescence, we localized VIPP1 to distinct spots within the chloroplast. In VIPP1-RNA interference/artificial microRNA cells, we consistently observed aberrant, prolamellar body-like structures at the origin of multiple thylakoid membrane layers, which appear to coincide with the immunofluorescent VIPP1 spots and suggest a defect in thylakoid membrane biogenesis. Accordingly, using quantitative shotgun proteomics, we found that unstressed vipp1 mutant cells accumulate 14 to 20% less photosystems, cytochrome b(6)f complex, and ATP synthase but 30% more light-harvesting complex II than control cells, while complex assembly, thylakoid membrane ultrastructure, and bulk lipid composition appeared unaltered. Photosystems in vipp1 mutants are sensitive to high light, which coincides with a lowered midpoint potential of the Q(A)/Q(A)(-) redox couple and increased thermosensitivity of photosystem II (PSII), suggesting structural defects in PSII. Moreover, swollen thylakoids, despite reduced membrane energization, in vipp1 mutants grown on ammonium suggest defects in the supermolecular organization of thylakoid membrane complexes. Overall, our data suggest a role of VIPP1 in the biogenesis/assembly of thylakoid membrane core complexes, most likely by supplying structural lipids.
Max-Planck-Institut für Molekulare Pflanzenphysiologie, D-14476 Potsdam-Golm, Germany.
André
A
Nordhues
Mark Aurel
MA
Schöttler
Ann-Katrin
AK
Unger
Stefan
S
Geimer
Stephanie
S
Schönfelder
Stefan
S
Schmollinger
Mark
M
Rütgers
Giovanni
G
Finazzi
Barbara
B
Soppa
Frederik
F
Sommer
Timo
T
Mühlhaus
Thomas
T
Roach
Anja
A
Krieger-Liszkay
Heiko
H
Lokstein
José Luis
JL
Crespo
Michael
M
Schroda
D002696:Chlamydomonas / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant; D008027:Light; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D040901:Proteomics; D034622:RNA Interference; D020524:Thylakoids / Q000378:metabolism* / Q000648:ultrastructure
D008565:Membrane Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins