HMA1, a new Cu-ATPase of the chloroplast envelope, is essential for growth under adverse light conditions.
Although ions play important roles in the cell and chloroplast metabolism, little is known about ion transport across the chloroplast envelope. Using a proteomic approach specifically targeted to the Arabidopsis chloroplast envelope, we have identified HMA1, which belongs to the metal-transporting P1B-type ATPases family. HMA1 is mainly expressed in green tissues, and we validated its chloroplast envelope localization. Yeast expression experiments demonstrated that HMA1 is involved in copper homeostasis and that deletion of its N-terminal His-domain partially affects the metal transport. Characterization of hma1 Arabidopsis mutants revealed a lower chloroplast copper content and a diminution of the total chloroplast superoxide dismutase activity. No effect was observed on the plastocyanin content in these lines. The hma1 insertional mutants grew like WT plants in standard condition but presented a photosensitivity phenotype under high light. Finally, direct biochemical ATPase assays performed on purified chloroplast envelope membranes showed that the ATPase activity of HMA1 is specifically stimulated by copper. Our results demonstrate that HMA1 offers an additional way to the previously characterized chloroplast envelope Cu-ATPase PAA1 to import copper in the chloroplast.
Seigneurin-Berny
Daphné
D
Laboratoire de Physiologie Cellulaire Végétale, Unité Mixte de Recherche 5168 CNRS/CEA/Institut National de la Recherche Agronomique, Université Joseph Fourier, Département Réponse et Dynamique Cellulaires (DRDC)/CEA-Grenoble, France. daphne.berny@cea.fr
Gravot
Antoine
A
Auroy
Pascaline
P
Mazard
Christophe
C
Kraut
Alexandra
A
Finazzi
Giovanni
G
Grunwald
Didier
D
Rappaport
Fabrice
F
Vavasseur
Alain
A
Joyard
Jacques
J
Richaud
Pierre
P
Rolland
Norbert
N
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000502:physiology*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000502:physiology*; D027682:Cation Transport Proteins / Q000235:genetics / Q000502:physiology*; D002736:Chloroplasts / Q000201:enzymology*; D003001:Cloning, Molecular; D003300:Copper / Q000378:metabolism; D000073840:Copper-Transporting ATPases; D006706:Homeostasis; D017136:Ion Transport; D008027:Light; D008969:Molecular Sequence Data; D009154:Mutation; D009685:Nuclear Envelope / Q000201:enzymology; D010940:Plant Proteins / Q000502:physiology; D013482:Superoxide Dismutase / Q000378:metabolism; D015003:Yeasts / Q000235:genetics
D029681:Arabidopsis Proteins; D027682:Cation Transport Proteins; D010940:Plant Proteins; D003300:Copper; D013482:Superoxide Dismutase; D000251:Adenosine Triphosphatases; C509978:HMA1 protein, Arabidopsis; D000073840:Copper-Transporting ATPases