Arabidopsis peroxisomal malate dehydrogenase functions in beta-oxidation but not in the glyoxylate cycle.
The aim was to determine the function of peroxisomal NAD(+)-malate dehydrogenase (PMDH) in fatty acid beta-oxidation and the glyoxylate cycle in Arabidopsis. Seeds in which both PMDH genes are disrupted by T-DNA insertions germinate, but seedling establishment is dependent on exogenous sugar. Mutant seedlings mobilize their triacylglycerol very slowly and growth is insensitive to 2,4-dichlorophenoxybutyric acid. Thus mutant seedlings are severely impaired in beta-oxidation, even though microarray analysis shows that beta-oxidation genes are expressed normally. The mutant phenotype was complemented by expression of a cDNA encoding PMDH with either its native peroxisome targeting signal-2 (PTS2) targeting sequence or a heterologous PTS1 sequence. In contrast to the block in beta-oxidation in mutant seedlings, [(14)C]acetate is readily metabolized into sugars and organic acids, thereby demonstrating normal activity of the glyoxylate cycle. We conclude that PMDH serves to reoxidize NADH produced from fatty acid beta-oxidation and does not participate directly in the glyoxylate cycle.
Pracharoenwattana
Itsara
I
Institute of Molecular Plant Sciences, School of Biological Sciences, University of Edinburgh, The King's Buildings, Edinburgh EH9 3JH, UK.
Cornah
Johanna E
JE
Smith
Steven M
SM
D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D018506:Gene Expression Regulation, Plant; D006038:Glyoxylates / Q000378:metabolism*; D008291:Malate Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D010084:Oxidation-Reduction; D020675:Peroxisomes / Q000201:enzymology*; D013395:Sucrose / Q000378:metabolism
D029681:Arabidopsis Proteins; D006038:Glyoxylates; D013395:Sucrose; D008291:Malate Dehydrogenase; C521419:PMDH1 protein, Arabidopsis; C521420:PMDH2 protein, Arabidopsis; C031150:glyoxylic acid