title: PETO Interacts with Other Effectors of Cyclic Electron Flow in Chlamydomonas.
abstract: While photosynthetic linear electron flow produces both ATP and NADPH, cyclic electron flow (CEF) around photosystem I (PSI) and cytochrome b6f generates only ATP. CEF is thus essential to balance the supply of ATP and NADPH for carbon fixation; however, it remains unclear how the system tunes the relative levels of linear and cyclic flow. Here, we show that PETO, a transmembrane thylakoid phosphoprotein specific of green algae, contributes to the stimulation of CEF when cells are placed in anoxia. In oxic conditions, PETO co-fractionates with other thylakoid proteins involved in CEF (ANR1, PGRL1, FNR). In PETO-knockdown strains, interactions between these CEF proteins are affected. Anoxia triggers a reorganization of the membrane, so that a subpopulation of PSI and cytochrome b6f now co-fractionates with the CEF effectors in sucrose gradients. The absence of PETO impairs this reorganization. Affinity purification identifies ANR1 as a major interactant of PETO. ANR1 contains two ANR domains, which are also found in the N-terminal region of NdhS, the ferredoxin-binding subunit of the plant ferredoxin-plastoquinone oxidoreductase (NDH). We propose that the ANR domain was co-opted by two unrelated CEF systems (PGR and NDH), possibly as a sensor of the redox state of the membrane.
authors.affiliation: Institut de Biologie Physico-Chimique, UMR 7141 CNRS-UPMC, 13 rue P et M Curie, Paris 75005, France.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Takahashi
authors.affiliation: Molecular Biotechnology and Systems Biology, University of Kaiserslautern, Kaiserlautern 67663, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Schmollinger
authors.affiliation: Department of Botany, University of British Columbia, Vancouver, BC V6T1Z4, Canada.
authors.forename: Jae-Hyeok
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Molecular Biotechnology and Systems Biology, University of Kaiserslautern, Kaiserlautern 67663, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Schroda
authors.affiliation: Institut de Biologie Physico-Chimique, UMR 7141 CNRS-UPMC, 13 rue P et M Curie, Paris 75005, France.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Rappaport
authors.affiliation: Institut de Biologie Physico-Chimique, UMR 7141 CNRS-UPMC, 13 rue P et M Curie, Paris 75005, France.
authors.forename: Francis-André
authors.initials: FA
authors.lastname: Wollman
authors.affiliation: Institut de Biologie Physico-Chimique, UMR 7141 CNRS-UPMC, 13 rue P et M Curie, Paris 75005, France. Electronic address: ovallon@ibpc.fr.
authors.forename: Olivier
authors.initials: O
authors.lastname: Vallon
mesh_terms: D002696:Chlamydomonas / Q000166:cytology / Q000378:metabolism*; D004579:Electron Transport; D055785:Gene Knockdown Techniques; D010100:Oxygen / Q000378:metabolism; D010750:Phosphoproteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D020524:Thylakoids / Q000378:metabolism*
chemical_list: D010750:Phosphoproteins; D010940:Plant Proteins; D010100:Oxygen
keywords: STT7; chlorophyll fluorescence; state transition; sucrose gradient ultracentrifugation; time-resolved spectroscopy; tridecyl-maltoside