title: Fine-tuned regulation of the K+/H+antiporter KEA3 is required to optimize photosynthesis during induction.
abstract: KEA3 is a thylakoid membrane localized K+/H+antiporter that regulates photosynthesis by modulating two components of proton motive force (pmf), the proton gradient (∆pH) and the electric potential (∆ψ). We identified a mutant allele of KEA3, disturbed proton gradient regulation (dpgr) based on its reduced non-photochemical quenching (NPQ) in artificial (CO2-free with low O2) air. This phenotype was enhanced in the mutant backgrounds of PSI cyclic electron transport (pgr5 and crr2-1). In ambient air, reduced NPQ was observed during induction of photosynthesis in dpgr, the phenotype that was enhanced after overnight dark adaptation. In contrast, the knockout allele of kea3-1 exhibited a high-NPQ phenotype during steady state in ambient air. Consistent with this kea3-1 phenotype in ambient air, the membrane topology of KEA3 indicated a proton efflux from the thylakoid lumen to the stroma. The dpgr heterozygotes showed a semidominant and dominant phenotype in artificial and ambient air, respectively. In dpgr, the protein level of KEA3 was unaffected but the downregulation of its activity was probably disturbed. Our findings suggest that fine regulation of KEA3 activity is necessary for optimizing photosynthesis.
authors: Department of Botany, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan.
authors: Caijuan
authors: C
authors: Wang
authors: Department of Botany, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan.|CREST, Japan Science and Technology Agency, Chiyoda-ku, Tokyo, 102-0076, Japan.
authors: Hiroshi
authors: H
authors: Yamamoto
authors: Graduate School of Sciences, Nara Institute of Science and Technology, Ikoma, Nara, 630-0101, Japan.|Sakai City Institute of Public Health, Sakai, Osaka, 590-0953, Japan.
authors: Fumika
authors: F
authors: Narumiya
authors: Graduate School of Sciences, Nara Institute of Science and Technology, Ikoma, Nara, 630-0101, Japan.|Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, Sandan, Hyogo, 669-1337, Japan.
authors: Yuri Nakajima
authors: YN
authors: Munekage
authors: UMR 5168 Laboratoire de Physiologie Cellulaire Végétale (LPCV) CNRS/UJF/INRA/CEA, Institut de Recherches en Technologies et Sciences pour le Vivant (iRTSV), CEA Grenoble, 38054, Grenoble, France.
authors: Giovanni
authors: G
authors: Finazzi
authors: Department of Biology, University of Padova, Padova, 35121, Italy.
authors: Ildiko
authors: I
authors: Szabo
authors: Department of Botany, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan.|CREST, Japan Science and Technology Agency, Chiyoda-ku, Tokyo, 102-0076, Japan.
authors: Toshiharu
authors: T
authors: Shikanai
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D004579:Electron Transport / Q000235:genetics / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D015151:Immunoblotting; D008027:Light; D009154:Mutation; D010100:Oxygen / Q000378:metabolism; D010641:Phenotype; D010788:Photosynthesis / Q000235:genetics*; D045331:Photosystem I Protein Complex / Q000235:genetics / Q000378:metabolism; D027961:Potassium-Hydrogen Antiporters / Q000235:genetics* / Q000378:metabolism; D018892:Proton-Motive Force / Q000235:genetics / Q000528:radiation effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020524:Thylakoids / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C000589494:KEA3 protein, Arabidopsis; D045331:Photosystem I Protein Complex; D027961:Potassium-Hydrogen Antiporters; D002245:Carbon Dioxide; D010100:Oxygen
keywords: 
  Arabidopsis thaliana
  ; KEA3; ion antiporter; photosynthesis; proton motive force