Journal
PLANT JOURNAL
Volume 50, Issue 3, Pages 381-390Publisher
BLACKWELL PUBLISHING
DOI: 10.1111/j.1365-313X.2007.03055.x
Keywords
peroxisome; malate dehydrogenase; beta-oxidation; glyoxylate cycle; fatty acids; Arabidopsis
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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, [C-14]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.
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