title: The Arabidopsis ALDP protein homologue COMATOSE is instrumental in peroxisomal acetate metabolism.
abstract: The Arabidopsis acn (acetate non-utilizing) mutants were isolated by fluoroacetate-resistant germination and seedling establishment. We report the characterization of the acn2 mutant. Physiological analyses of acn2 showed that it possessed characteristics similar to those of the mutants cts (COMATOSE)-1 and pxa [peroxisomal ABC (ATP-binding-cassette) transporter]1. The acn2 locus was mapped to within 3 cM of the CTS gene on the bottom arm of chromosome IV using CAPS (cleavage amplification polymorphism) and SSLP (simple sequence-length polymorphism) markers. Crossing acn2 and cts-1 failed to restore the fluoroacetate-sensitive phenotype, suggesting that these mutations were allelic. Sequencing of the ACN2 locus revealed a C-->T nonsense mutation in exon 13, which would have resulted in the elimination of the C-terminal hemitransporter domain of the encoded protein. Neither the full-length CTS protein nor the truncated protein was detected on immunoblots using either C-terminal- or N-terminal-specific anti-CTS antibodies respectively, demonstrating the absence of the entire CTS protein in acn2 mutants. Emerged seedlings of both cts-1 and pxa1 alleles displayed increased resistance to FAc (monofluoroacetic acid) compared with the corresponding wild-type seedlings. Complementation studies showed that mutation of the CTS gene was responsible for the FAc-resistant phenotype, as when the wild-type protein was expressed in both the cts-1 and pxa1 mutant lines, the strains became FAc-sensitive. Feeding studies confirmed that both acn2 and cts-1 mutants were compromised in their ability to convert radiolabelled acetate into soluble carbohydrate. These results demonstrate a role for the ABC protein CTS in providing acetate to the glyoxylate cycle in developing seedlings.
authors.affiliation: School of Biological Sciences, University of Wales Bangor, Bangor, Gwynedd LL57 2UW, Wales, UK. m.a.hooks@bangor.ac.uk
authors.forename: Mark A
authors.initials: MA
authors.lastname: Hooks
authors.forename: James E
authors.initials: JE
authors.lastname: Turner
authors.forename: Elaine C
authors.initials: EC
authors.lastname: Murphy
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Johnston
authors.forename: Sally
authors.initials: S
authors.lastname: Burr
authors.forename: Szymon
authors.initials: S
authors.lastname: Jarosławski
mesh_terms: D000074063:ATP Binding Cassette Transporter, Subfamily D, Member 1; D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000502:physiology*; D000085:Acetates / Q000378:metabolism*; D000251:Adenosine Triphosphatases; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000502:physiology*; D002460:Cell Line; D018389:Codon, Nonsense; D050612:Fatty Acid Transport Proteins / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D018525:Germination; D020675:Peroxisomes / Q000378:metabolism*; D010641:Phenotype; D030821:Plants, Genetically Modified; D036226:Seedlings / Q000502:physiology*
chemical_list: C115572:ABCD1 protein, human; D000074063:ATP Binding Cassette Transporter, Subfamily D, Member 1; D018528:ATP-Binding Cassette Transporters; D000085:Acetates; D029681:Arabidopsis Proteins; D018389:Codon, Nonsense; D050612:Fatty Acid Transport Proteins; D000251:Adenosine Triphosphatases; C456843:At4g39850 protein, Arabidopsis