Identification of a New Component of the Photorespiratory C2 Cycle in Arabidopsis and Analysis of its Function in Metabolism
Zusammenfassung der Projektergebnisse
The photorespiratory Arabidopsis 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 ß-ketoacyl- [acyl carrier protein] (ACP) synthase (mtKAS), a key enzyme of the mitochondrial fatty acid biosynthetic system. Its major product, 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 (PDH) and ?-ketoglutarate dehydrogenase (KDH). This view is in conflict with the fact that the mtkas-1 mutant and two allelic T-DNA knockout mutants grow well under non-photorespiratory conditions. On the molecular level, the mutants show residual lipoylation of H-protein, i.e., the mutation does not lead to a full functional knockout of GDC. Lipoylation of the PDH and KDH E2 subunits is distinctly less affected than that of H-protein. These and other data suggest that mitochondrial protein lipoylation in plants, in contrast to current thinking, may not exclusively depend on the mtKAS pathway of fatty acid biosynthesis.
Projektbezogene Publikationen (Auswahl)
- (2006) The plant-like C2 glycolate pathway and the bacterial-like glycerate cycle cooperate in phosphoglycolate metabolism in cyanobacteria. Plant Physiology 142: 333-342
Eisenhut M, Kahlon S, Hasse D, Ewald R, Lieman-Hurwitz J, Ogawa T, Ruth W, Bauwe H, Kaplan A, Hagemann M
- (2007) Mitochondrial protein lipoylation does not exclusively depend on the mtKAS pathway of de-novo fatty acid synthesis in Arabidopsis. Plant Physiology, 145: 41-48
Ewald R, Kolukisaoglu Ü, Bauwe U, Mikkat S, Bauwe H
