The GMD1 and GMD2 genes of Arabidopsis encode isoforms of GDP-D-mannose 4,6-dehydratase with cell type-specific expression patterns.
l-Fucose (l-Fuc) is a monosaccharide constituent of plant cell wall polysaccharides and glycoproteins. The committing step in the de novo synthesis of l-Fuc is catalyzed by GDP-d-mannose 4,6-dehydratase, which, in Arabidopsis, is encoded by the GMD1 and GMD2 (MUR1) genes. To determine the functional significance of this genetic redundancy, the expression patterns of both genes were investigated via promoter-beta-glucuronidase fusions and immunolocalization of a Fuc-containing epitope. GMD2 is expressed in most cell types of the root, with the notable exception of the root tip where strong expression of GMD1 is observed. Within shoot organs, GMD1::GUS expression is confined to stipules and pollen grains leading to fucosylation of the walls of these cell types in the mur1 mutant. These results suggest that GMD2 represents the major housekeeping gene for the de novo synthesis of GDP-l-Fuc, whereas GMD1 expression is limited to a number of specialized cell types. We conclude that the synthesis of GDP-l-Fuc is controlled in a cell-autonomous manner by differential expression of two isoforms of the same enzyme.
Bonin
Christopher P
CP
Department of Molecular and Cell Biology, University of Connecticut, Storrs 06269, USA.
Freshour
Glenn
G
Hahn
Michael G
MG
Vanzin
Gary F
GF
Reiter
Wolf-Dieter
WD
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000166:cytology / Q000201:enzymology* / Q000235:genetics; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D035264:Flowers / Q000201:enzymology; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D005966:Glucuronidase / Q000235:genetics; D006836:Hydro-Lyases / Q000737:chemistry / Q000235:genetics*; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics; D008969:Molecular Sequence Data; D018515:Plant Leaves / Q000201:enzymology; D018517:Plant Roots / Q000201:enzymology; D018547:Plant Stems / Q000201:enzymology; D030821:Plants, Genetically Modified / Q000201:enzymology; D018749:RNA, Plant / Q000235:genetics / Q000302:isolation & purification; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D017931:DNA Primers; D007527:Isoenzymes; D018749:RNA, Plant; D005966:Glucuronidase; C422948:GDP-D-mannose dehydratase, bacteria; D006836:Hydro-Lyases