title: Role of thylakoid ATP/ADP carrier in photoinhibition and photoprotection of photosystem II in Arabidopsis.
abstract: The chloroplast thylakoid ATP/ADP carrier (TAAC) belongs to the mitochondrial carrier superfamily and supplies the thylakoid lumen with stromal ATP in exchange for ADP. Here, we investigate the physiological consequences of TAAC depletion in Arabidopsis (Arabidopsis thaliana). We show that the deficiency of TAAC in two T-DNA insertion lines does not modify the chloroplast ultrastructure, the relative amounts of photosynthetic proteins, the pigment composition, and the photosynthetic activity. Under growth light conditions, the mutants initially displayed similar shoot weight, but lower when reaching full development, and were less tolerant to high light conditions in comparison with the wild type. These observations prompted us to study in more detail the effects of TAAC depletion on photoinhibition and photoprotection of the photosystem II (PSII) complex. The steady-state phosphorylation levels of PSII proteins were not affected, but the degradation of the reaction center II D1 protein was blocked, and decreased amounts of CP43-less PSII monomers were detected in the mutants. Besides this, the mutant leaves displayed a transiently higher nonphotochemical quenching of chlorophyll fluorescence than the wild-type leaves, especially at low light. This may be attributed to the accumulation in the absence of TAAC of a higher electrochemical H(+) gradient in the first minutes of illumination, which more efficiently activates photoprotective xanthophyll cycle-dependent and independent mechanisms. Based on these results, we propose that TAAC plays a critical role in the disassembly steps during PSII repair and in addition may balance the trans-thylakoid electrochemical H(+) gradient storage.
authors.affiliation: Division of Molecular Genetics, Department of Physics, Chemistry, and Biology, Linköping University, 581 83 Linkoping, Sweden.
authors.forename: Lan
authors.initials: L
authors.lastname: Yin
authors.forename: Björn
authors.initials: B
authors.lastname: Lundin
authors.forename: Martine
authors.initials: M
authors.lastname: Bertrand
authors.forename: Markus
authors.initials: M
authors.lastname: Nurmi
authors.forename: Katalin
authors.initials: K
authors.lastname: Solymosi
authors.forename: Saijaliisa
authors.initials: S
authors.lastname: Kangasjärvi
authors.forename: Eva-Mari
authors.initials: EM
authors.lastname: Aro
authors.forename: Benoît
authors.initials: B
authors.lastname: Schoefs
authors.forename: Cornelia
authors.initials: C
authors.lastname: Spetea
mesh_terms: D017920:Antiporters / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics; D008027:Light; D016254:Mutagenesis, Insertional; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000378:metabolism* / Q000528:radiation effects; D020524:Thylakoids / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D017920:Antiporters; D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; D045332:Photosystem II Protein Complex; C036483:T-DNA; C519172:TAAC protein, Arabidopsis