title: AtPHT4;4 is a chloroplast-localized ascorbate transporter in Arabidopsis.
abstract: Ascorbate is an antioxidant and coenzyme for various metabolic reactions in vivo. In plant chloroplasts, high ascorbate levels are required to overcome photoinhibition caused by strong light. However, ascorbate is synthesized in the mitochondria and the molecular mechanisms underlying ascorbate transport into chloroplasts are unknown. Here we show that AtPHT4;4, a member of the phosphate transporter 4 family of Arabidopsis thaliana, functions as an ascorbate transporter. In vitro analysis shows that proteoliposomes containing the purified AtPHT4;4 protein exhibit membrane potential- and Cl(-)-dependent ascorbate uptake. The AtPHT4;4 protein is abundantly expressed in the chloroplast envelope membrane. Knockout of AtPHT4;4 results in decreased levels of the reduced form of ascorbate in the leaves and the heat dissipation process of excessive energy during photosynthesis is compromised. Taken together, these observations indicate that the AtPHT4;4 protein is an ascorbate transporter at the chloroplast envelope membrane, which may be required for tolerance to strong light stress.
authors.affiliation: Advanced Science Research Center, Okayama University, Okayama 700-8530, Japan.
authors.forename: Takaaki
authors.initials: T
authors.lastname: Miyaji
authors.affiliation: Gene Discovery Research Group, RIKEN Center for Sustainable Resource Science, Yokohama 230-0045, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kuromori
authors.affiliation: Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Takeuchi
authors.affiliation: Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Yamaji
authors.affiliation: Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan.
authors.forename: Kengo
authors.initials: K
authors.lastname: Yokosho
authors.affiliation: Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Shimazawa
authors.affiliation: Gene Discovery Research Group, RIKEN Center for Sustainable Resource Science, Yokohama 230-0045, Japan.
authors.forename: Eriko
authors.initials: E
authors.lastname: Sugimoto
authors.affiliation: Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Omote
authors.affiliation: Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan.
authors.forename: Jian Feng
authors.initials: JF
authors.lastname: Ma
authors.affiliation: Gene Discovery Research Group, RIKEN Center for Sustainable Resource Science, Yokohama 230-0045, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Shinozaki
authors.affiliation: 1] Advanced Science Research Center, Okayama University, Okayama 700-8530, Japan [2] Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Moriyama
mesh_terms: D027321:Anion Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001205:Ascorbic Acid / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D005453:Fluorescence; D055786:Gene Knockout Techniques; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008027:Light; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D016133:Polymerase Chain Reaction; D013312:Stress, Physiological / Q000235:genetics
chemical_list: D027321:Anion Transport Proteins; D029681:Arabidopsis Proteins; D017931:DNA Primers; D018076:DNA, Complementary; D026901:Membrane Transport Proteins; C000603323:PHT4;4 protein, Arabidopsis; D001205:Ascorbic Acid