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Nat Commun. 2015 Jan 5;6:5928. doi: 10.1038/ncomms6928.

AtPHT4;4 is a chloroplast-localized ascorbate transporter in Arabidopsis.

Author information

1
Advanced Science Research Center, Okayama University, Okayama 700-8530, Japan.
2
Gene Discovery Research Group, RIKEN Center for Sustainable Resource Science, Yokohama 230-0045, Japan.
3
Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan.
4
Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan.
5
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.

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.

PMID:
25557369
PMCID:
PMC4308718
DOI:
10.1038/ncomms6928
[Indexed for MEDLINE]
Free PMC Article

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