The Arabidopsis thaliana multifunctional protein gene (MFP2) of peroxisomal β‐oxidation is essential for seedling establishment

Abstract

SummaryThe multifunctional protein (MFP) of peroxisomal b-oxidation catalyses four separate reactions, two of which (2-trans enoyl-CoA hydratase and L-3-hydroxyacyl-CoA dehydrogenase) are core activities required for the catabolism of all fatty acids. We have isolated and characterized five Arabidopsis thaliana mutants in the MFP2 gene that is expressed predominantly in germinating seeds. Seedlings of mfp2 require an exogenous supply of sucrose for seedling establishment to occur. Analysis of mfp2-1 seedlings revealed that seed storage lipid was catabolized more slowly, long-chain acyl-CoA substrates accumulated and there was an increase in peroxisome size. Despite a reduction in the rate of b-oxidation, mfp2 seedlings are not resistant to the herbicide 2,4-dichlorophenoxybutyric acid, which is catabolized to the auxin 2,4-dichlorophenoxyacetic acid by b-oxidation. Acyl-CoA feeding experiments show that the MFP2 2-trans enoyl-CoA hydratase only exhibits activity against long chain (C18:0) substrates, whereas the MFP2 L-3-hydroxyacyl-CoA dehydrogenase is active on C6:0, C12:0 and C18:0 substrates. A mutation in the abnormal inflorescence meristem gene AIM1, the only homologue of MFP2, results in an abnormal inflorescence meristem phenotype in mature plants (Richmond and Bleecker, Plant Cell 11, 1999, 1911) demonstrating that the role of these genes is very different. The mfp2-1 aim1 double mutant aborted during the early stages of embryo development showing that these two proteins share a common function that is essential for this key stage in the life cycle.

The activity of the glyoxylate cycle in peroxisomes of Candida albicans depends on a functional β-oxidation pathway: evidence for reduced metabolite transport across the peroxisomal membrane

“…The glyoxylate cycle is peroxisomal in C. albicans been observed in yeast, mammals and plants that mutants with a deficiency in peroxisomal b-oxidation exhibit a changed peroxisome size and abundance (Chang et al, 1999;Germain et al, 2001;Rylott et al, 2006;Smith et al, 2000). These observations prompted us to investigate peroxisome morphology in the fox2D/D strain (Fig.…”

Mitochondrial Protein Lipoylation Does Not Exclusively Depend on the mtKAS Pathway of de Novo Fatty Acid Synthesis in Arabidopsis

“…Plastidal de novo synthesis and export of fatty acids (Koo et al, 2004) including lipoate (Yasuno and Wada, 2002) would be one possible source. Alternatively, and possibly more likely, octanoyl chains could be supplied from the b-oxidation of longer-chain fatty acids in peroxisomes (Graham and Eastmond, 2002;Rylott et al, 2006). Lipoate synthase has been identified in plant mitochondria (Yasuno and Wada, 1998); however, such a scavenging pathway would also require lipoyl-protein ligase (LPLA).…”

The Multifunctional Protein in Peroxisomal β-Oxidation

“…Mutations in the AtMFP2 gene give rise to a sucrose-dependent seedling phenotype (11), whereas AtAIM1 disruption causes abnormal inflorescence development resulting in low fertility (3). The different phenotypes reveal the diverse physiological roles of the two genes.…”

“…The different phenotypes reveal the diverse physiological roles of the two genes. In vivo and in vitro characterization of the chain length specificity of AtMFP2 suggests a long chain hydratase coupled to a short, medium, and long chain-specific dehydrogenase (11). AtAIM1 seems to have higher affinity for short chain acylCoA, although aim1 plants have elevated levels of C18:1 and C18:2 unsaturated fatty acids (3).…”

“…Both AtAIM1 and AtMFP2 are expressed at approximately equal levels in roots, rosette leaves, flowers, and siliques (3). A complete block in ␤-oxidation by the introduction of an AtAIM1/AtMFP2 double mutation results in nonviable embryos aborting at an early stage of embryo development (11).…”