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BIOCHEMICAL PROCESSES AND MACROMOLECULAR STRUCTURES

Functions of Chloroplastic Adenylate Kinases in Arabidopsis^1,[W],[OA]

Max-Planck-Institut für Molekulare Pflanzenphysiologie, 14476 Golm, Germany (P.R.L., C.G., R.Z.); and Freie Universität Berlin, Institut für Biologie, Pflanzenphysiologie, 14195 Berlin, Germany (G.T.)

Adenosine monophosphate kinase (AMK; adenylate kinase) catalyses the reversible formation of ADP by the transfer of one phosphate group from ATP to AMP, thus equilibrating adenylates. The Arabidopsis (Arabidopsis thaliana) genome contains 10 genes with an adenylate/cytidylate kinase signature; seven of these are identified as putative adenylate kinases. Encoded proteins of at least two members of this Arabidopsis adenylate kinase gene family are targeted to plastids. However, when the individual genes are disrupted, the phenotypes of both mutants are strikingly different. Although absence of AMK2 causes only 30% reduction of total adenylate kinase activity in leaves, there is loss of chloroplast integrity leading to small, pale-looking plantlets from embryo to seedling development. In contrast, no phenotype for disruption of the second plastid adenylate kinase was found. From this analysis, we conclude that AMK2 is the major activity for equilibration of adenylates and de novo synthesis of ADP in the plastid stroma.

² Present address: Leibniz-Institut für Pflanzenbiochemie, Weinberg 3, 06120 Halle, Germany.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Rita Zrenner (zrenner{at}mpimp-golm.mpg.de).

^[W] The online version of this article contains Web-only data.

^[OA] Open Access articles can be viewed online without a subscription.

www.plantphysiol.org/cgi/doi/10.1104/pp.107.114702

^* Corresponding author; e-mail zrenner{at}mpimp-golm.mpg.de.

Received December 7, 2007; accepted December 21, 2007; published December 27, 2007.