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BIOENERGETICS AND PHOTOSYNTHESIS

Mitochondrial Protein Lipoylation Does Not Exclusively Depend on the mtKAS Pathway of de Novo Fatty Acid Synthesis in Arabidopsis^1,[W],[OA]

Department of Plant Physiology, University of Rostock, D–18059 Rostock, Germany (R.E., Ü.K., U.B., H.B.); and Core Facility Proteome Analytics, Medical Faculty, University of Rostock, D–18057 Rostock, Germany (S.M.)

The photorespiratory Arabidopsis (Arabidopsis thaliana) mutant gld1 (now designated mtkas-1) is deficient in glycine decarboxylase (GDC) activity, but the exact nature of the genetic defect was not known. We have identified the mtkas-1 locus as gene At2g04540, which encodes -ketoacyl-[acyl carrier protein (ACP)] synthase (mtKAS), a key enzyme of the mitochondrial fatty acid synthetic system. One of its major products, octanoyl-ACP, is regarded as essential for the intramitochondrial lipoylation of several proteins including the H-protein subunit of GDC and the dihydrolipoamide acyltransferase (E2) subunits of two other essential multienzyme complexes, pyruvate dehydrogenase and -ketoglutarate dehydrogenase. This view is in conflict with the fact that the mtkas-1 mutant and two allelic T-DNA knockout mutants grow well under nonphotorespiratory conditions. Although on a very low level, the mutants show residual lipoylation of H protein, indicating that the mutation does not lead to a full functional knockout of GDC. Lipoylation of the pyruvate dehydrogenase and -ketoglutarate dehydrogenase E2 subunits is distinctly less reduced than that of H protein in leaves and remains unaffected from the mtKAS knockout in roots. These data suggest that mitochondrial protein lipoylation does not exclusively depend on the mtKAS pathway of lipoate biosynthesis in leaves and may occur independently of this pathway in roots.

² Present address: Center for Life Science Automation, F.-Barnewitz-Str. 8, D–18119 Rostock, 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: Hermann Bauwe (hermann.bauwe{at}uni-rostock.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.107.104000

^* Corresponding author; e-mail hermann.bauwe{at}uni-rostock.de.

Received June 14, 2007; accepted June 27, 2007; published July 6, 2007.