Linked Life Data

16595667

Source:http://linkedlifedata.com/resource/pubmed/id/16595667

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
23
pubmed:dateCreated
2006-6-5
pubmed:abstractText
In plants, a proposed ascorbate (vitamin C) biosynthesis pathway occurs via GDP-D-mannose (GDP-D-Man), GDP-L-galactose (GDP-L-Gal), and L-galactose. However, the steps involved in the synthesis of L-Gal from GDP-L-Gal in planta are not fully characterized. Here we present evidence for an in vivo role for L-Gal-1-P phosphatase in plant ascorbate biosynthesis. We have characterized a low ascorbate mutant (vtc4-1) of Arabidopsis thaliana, which exhibits decreased ascorbate biosynthesis. Genetic mapping and sequencing of the VTC4 locus identified a mutation (P92L) in a gene with predicted L-Gal-1-P phosphatase activity (At3g02870). Pro-92 is within a beta-bulge that is conserved in related myo-inositol monophosphatases. The mutation is predicted to disrupt the positioning of catalytic amino acid residues within the active site. Accordingly, L-Gal-1-P phosphatase activity in vtc4-1 was approximately 50% of wild-type plants. In addition, vtc4-1 plants incorporate significantly more radiolabel from [2-(3)H]Man into L-galactosyl residues suggesting that the mutation increases the availability of GDP-L-Gal for polysaccharide synthesis. Finally, a homozygous T-DNA insertion line, which lacks a functional At3g02870 gene product, is also ascorbate-deficient (50% of wild type) and deficient in L-Gal-1-P phosphatase activity. Genetic complementation tests revealed that the insertion mutant and VTC4-1 are alleles of the same genetic locus. The significantly lower ascorbate and perturbed L-Gal metabolism in vtc4-1 and the T-DNA insertion mutant indicate that L-Gal-1-P phosphatase plays a role in plant ascorbate biosynthesis. The presence of ascorbate in the T-DNA insertion mutant suggests there is a bypass to this enzyme or that other pathways also contribute to ascorbate biosynthesis.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jun
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
9
pubmed:volume
281
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
15662-70
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2006
pubmed:articleTitle
Arabidopsis thaliana VTC4 encodes L-galactose-1-P phosphatase, a plant ascorbic acid biosynthetic enzyme.
pubmed:affiliation
Department of Biological Sciences, State University of New York, Cortland, New York 13045, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, Non-P.H.S., Research Support, Non-U.S. Gov't