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Toward the mechanism of NH(4) (+) sensitivity mediated by Arabidopsis GDP-mannose pyrophosphorylase.

Abstract
The ascorbic acid (AA)-deficient Arabidopsis thaliana mutant vtc1-1, which is defective in GDP-mannose pyrophosphorylase (GMPase), exhibits conditional hypersensitivity to ammonium (NH(4) (+) ), a phenomenon that is independent of AA deficiency. As GMPase is important for GDP-mannose biosynthesis, a nucleotide sugar necessary for protein N-glycosylation, it has been thought that GDP-mannose deficiency is responsible for the growth defect in vtc1-1 in the presence of NH(4) (+) . Therefore, the motivation for this work was to elucidate the growth and developmental processes that are affected in vtc1-1 in the presence of NH(4) (+) and to determine whether GDP-mannose deficiency generally causes NH(4) (+) sensitivity. Furthermore, as NH(4) (+) may alter cytosolic pH, we investigated the responses of vtc1-1 to pH changes in the presence and absence of NH(4) (+) . Using qRT-PCR and staining procedures, we demonstrate that defective N-glycosylation in vtc1-1 contributes to cell wall, membrane and cell cycle defects, resulting in root growth inhibition in the presence of NH(4) (+) . However, by using mutants acting upstream of vtc1-1 and contributing to GDP-mannose biosynthesis, we show that GDP-mannose deficiency does not generally lead to and is not the primary cause of NH(4) (+) sensitivity. Instead, our data suggest that GMPase responds to pH alterations in the presence of NH(4) (+) .
AuthorsChase F Kempinski, Rawaa Haffar, Carina Barth
JournalPlant, cell & environment (Plant Cell Environ) Vol. 34 Issue 5 Pg. 847-58 (May 2011) ISSN: 1365-3040 [Electronic] United States
PMID21332510 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Copyright© 2011 Blackwell Publishing Ltd.
Chemical References
  • Arabidopsis Proteins
  • Quaternary Ammonium Compounds
  • Guanosine Diphosphate Mannose
  • Nucleotidyltransferases
  • mannose 1-phosphate guanylyltransferase
  • Ascorbic Acid
Topics
  • Arabidopsis (enzymology, genetics, growth & development)
  • Arabidopsis Proteins (metabolism)
  • Ascorbic Acid (analysis)
  • Cell Cycle
  • Cell Membrane (metabolism)
  • Cell Wall (metabolism)
  • Endoplasmic Reticulum (metabolism)
  • Glycosylation
  • Guanosine Diphosphate Mannose (biosynthesis)
  • Hydrogen-Ion Concentration
  • Mutation
  • Nucleotidyltransferases (metabolism)
  • Plant Roots (growth & development)
  • Quaternary Ammonium Compounds (metabolism)
  • Stress, Physiological

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