title: A single amino acid alteration in PGR5 confers resistance to antimycin A in cyclic electron transport around PSI.
abstract: In Arabidopsis thaliana, the main route of cyclic electron transport around PSI is sensitive to antimycin A, but the site of inhibition has not been clarified. We discovered that ferredoxin-dependent plastoquinone reduction in ruptured chloroplasts was less sensitive to antimycin A in Arabidopsis that overaccumulated PGR5 (PROTON GRADIENT REGULATION 5) originating from Pinus taeda (PtPGR5) than that in the wild type. Consistent with this in vitro observation, infiltration of antimycin A reduced PSII yields and the non-photochemical quenching (NPQ) of Chl fluorescence in wild-type leaves but not in leaves accumulating PtPGR5. There are eight amino acid differences between PGR5 of Arabidopsis (AtPGR5) and PtPGR5 in their mature forms. To determine the site conferring antimycin A resistance, a series of AtPGR5 and PtPGR5 variants was introduced into the Arabidopsis pgr5 mutant. We determined that the presence of lysine rather than valine at the third amino acid position was necessary and sufficient for resistance to antimycin A. High levels of resistance to antimycin A required overaccumulation of PtPGR5 in ruptured chloroplasts, suggesting that PtPGR5 is partly resistant to antimycin A. In contrast, PSII yield was almost fully resistant to antimycin A in leaves accumulating endogenous levels of PtPGR5 or AtPGR5 V3K that had lysine instead of valine at the third position. NPQ was also dramatically recovered in leaves of these lines. These results imply that partial recovery of PSI cyclic electron transport is sufficient for maintaining redox homeostasis in photosynthesis. Our discovery suggests that antimycin A inhibits the function of PGR5 or proteins localized close to PGR5.
authors.affiliation: Department of Botany, Graduate School of Science, Kyoto University, Kyoto, 606-8502 Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Sugimoto
authors.forename: Yuki
authors.initials: Y
authors.lastname: Okegawa
authors.forename: Akihiko
authors.initials: A
authors.lastname: Tohri
authors.forename: Terri A
authors.initials: TA
authors.lastname: Long
authors.forename: Sarah F
authors.initials: SF
authors.lastname: Covert
authors.forename: Toru
authors.initials: T
authors.lastname: Hisabori
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Shikanai
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000935:Antifungal Agents / Q000494:pharmacology; D000968:Antimycin A / Q000494:pharmacology*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D002736:Chloroplasts / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D004351:Drug Resistance / Q000235:genetics*; D004579:Electron Transport / Q000187:drug effects; D005816:Genetic Complementation Test; D015151:Immunoblotting; D008969:Molecular Sequence Data; D009154:Mutation; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics* / Q000378:metabolism; D045331:Photosystem I Protein Complex / Q000235:genetics* / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000235:genetics / Q000378:metabolism; D041603:Pinus taeda / Q000235:genetics; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D017386:Sequence Homology, Amino Acid
chemical_list: D000935:Antifungal Agents; D029681:Arabidopsis Proteins; C465062:PGR5 protein, Arabidopsis; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D002734:Chlorophyll; D000968:Antimycin A
keywords: Antimycin A; Arabidopsis thaliana; Cyclic electron transport; FQR; PGR5; Pinus taeda