Identification of a New Component of the Photorespiratory C2 Cycle in Arabidopsis and Analysis of its Function in Metabolism
Final Report Abstract
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.
Publications
- (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
