The Biosynthesis of l-Arabinose in Plants: Molecular Cloning and Characterization of a Golgi-Localized UDP-d-Xylose 4-Epimerase Encoded by the MUR4 Gene of Arabidopsis

AUTOR(ES)

Burget, Emilie G.

FONTE

American Society of Plant Biologists

RESUMO

The mur4 mutant of Arabidopsis shows a 50% reduction in the monosaccharide l-Ara in leaf-derived cell wall material because of a partial defect in the 4-epimerization of UDP-d-Xyl to UDP-l-Ara. To determine the genetic lesion underlying the mur4 phenotype, the MUR4 gene was cloned by a map-based procedure and found to encode a type-II membrane protein with sequence similarity to UDP-d-Glc 4-epimerases. Enzyme assays of MUR4 protein expressed in the methylotropic yeast Pichia pastoris indicate that it catalyzes the 4-epimerization of UDP-d-Xyl to UDP-l-Ara, the nucleotide sugar used by glycosyltransferases in the arabinosylation of cell wall polysaccharides and wall-resident proteoglycans. Expression of MUR4–green fluorescent protein constructs in Arabidopsis revealed localization patterns consistent with targeting to the Golgi, suggesting that the MUR4 protein colocalizes with glycosyltransferases in the biosynthesis of arabinosylated cell wall components. The Arabidopsis genome encodes three putative proteins with >76% sequence identity to MUR4, which may explain why mur4 plants are not entirely deficient in the de novo synthesis of UDP-l-Ara.

Documentos Relacionados

• The Biosynthesis of d-Galacturonate in Plants. Functional Cloning and Characterization of a Membrane-Anchored UDP-d-Glucuronate 4-Epimerase from Arabidopsis1
• The Biosynthesis of UDP-Galacturonic Acid in Plants. Functional Cloning and Characterization of Arabidopsis UDP-d-Glucuronic Acid 4-Epimerase1
• Identification and Characterization of GONST1, a Golgi-Localized GDP-Mannose Transporter in Arabidopsis
• The mur4 Mutant of Arabidopsis Is Partially Defective in the de Novo Synthesis of Uridine Diphospho l-Arabinose1
• Fermentation of d-Xylose and l-Arabinose to Ethanol by Erwinia chrysanthemi