title: Identification and characterization of Arabidopsis AtNUDX9 as a GDP-d-mannose pyrophosphohydrolase: its involvement in root growth inhibition in response to ammonium.
abstract: GDP-d-mannose (GDP-d-Man) is an important intermediate in ascorbic acid (AsA) synthesis, cell wall synthesis, protein N-glycosylation, and glycosylphosphatidylinositol-anchoring in plants. Thus, the modulation of intracellular levels of GDP-d-Man could be important for maintaining various cellular processes. Here an Arabidopsis GDP-d-Man pyrophosphohydrolase, AtNUDX9 (AtNUDT9; At3g46200), which hydrolysed GDP-d-Man to GMP and mannose 1-phosphate, was identified. The K m and V max values for GDP-d-Man of AtNUDX9 were 376±24 μM and 1.61±0.15 μmol min(-1) mg(-1) protein, respectively. Among various tissues, the expression levels of AtNUDX9 and the total activity of GDP-d-Man pyrophosphohydrolase were the highest in the roots. The GDP-d-Man pyrophosphohydrolase activity was increased in the root of plants grown in the presence of ammonium. No difference was observed in the levels of AsA in the leaf and root tissues of the wild-type and knockout-nudx9 (KO-nudx9) plants, whereas a marked increase in N-glycoprotein levels and enhanced growth were detected in the roots of KO-nudx9 plants in the presence of ammonium. These results suggest that AtNUDX9 is involved in the regulation of GDP-d-Man levels affecting ammonium sensitivity via modulation of protein N-glycosylation in the roots.
authors.affiliation: Department of Advanced Bioscience, Faculty of Agriculture, Kinki University, 3327-204 Nakamachi, Nara 631-8505, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Tanaka
authors.affiliation: Department of Life Science and Biotechnology, Faculty of Life and Environmental Science, Shimane University, 1060 Nishikawatsu, Matsue, Shimane 690-8504, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Maruta
authors.affiliation: Department of Advanced Bioscience, Faculty of Agriculture, Kinki University, 3327-204 Nakamachi, Nara 631-8505, Japan.
authors.forename: Takahisa
authors.initials: T
authors.lastname: Ogawa
authors.affiliation: Department of Advanced Bioscience, Faculty of Agriculture, Kinki University, 3327-204 Nakamachi, Nara 631-8505, Japan.
authors.forename: Noriaki
authors.initials: N
authors.lastname: Tanabe
authors.affiliation: Department of Advanced Bioscience, Faculty of Agriculture, Kinki University, 3327-204 Nakamachi, Nara 631-8505, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Tamoi
authors.affiliation: Department of Food and Nutritional Science, College of Bioscience and Biotechnology, Chubu University,1200 Matsumoto-cho, Kasugai, Aichi, 487-8501 Japan.
authors.forename: Kazuya
authors.initials: K
authors.lastname: Yoshimura
authors.affiliation: Department of Advanced Bioscience, Faculty of Agriculture, Kinki University, 3327-204 Nakamachi, Nara 631-8505, Japan shigeoka@nara.kindai.ac.jp.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Shigeoka
mesh_terms: D064751:Ammonium Compounds / Q000378:metabolism*; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001205:Ascorbic Acid / Q000378:metabolism*; D006023:Glycoproteins / Q000378:metabolism*; D011755:Pyrophosphatases / Q000235:genetics* / Q000378:metabolism
chemical_list: D064751:Ammonium Compounds; D029681:Arabidopsis Proteins; D006023:Glycoproteins; C000608860:NUDX9 protein, Arabidopsis; D011755:Pyrophosphatases; D001205:Ascorbic Acid
keywords: Ammonium response; Arabidopsis; GDP-d-mannose pyrophosphohydrolase; Nudix hydrolase.; l-ascorbic acid; protein N-glycosylation