A functional analysis of the pyrimidine catabolic pathway in Arabidopsis.
* Reductive catabolism of pyrimidine nucleotides occurs via a three-step pathway in which uracil is degraded to beta-alanine, CO(2) and NH(3) through sequential activities of dihydropyrimidine dehydrogenase (EC 1.3.1.2, PYD1), dihydropyrimidinase (EC 3.5.2.2, PYD2) and beta-ureidopropionase (EC 3.5.1.6, PYD3). * A proposed function of this pathway, in addition to the maintenance of pyrimidine homeostasis, is the recycling of pyrimidine nitrogen to general nitrogen metabolism. PYD expression and catabolism of [2-(14)C]-uracil are markedly elevated in response to nitrogen limitation in plants, which can utilize uracil as a nitrogen source. * PYD1, PYD2 and PYD3 knockout mutants were used for functional analysis of this pathway in Arabidopsis. pyd mutants exhibited no obvious phenotype under optimal growing conditions. pyd2 and pyd3 mutants were unable to catabolize [2-(14)C]-uracil or to grow on uracil as the sole nitrogen source. By contrast, catabolism of uracil was reduced by only 40% in pyd1 mutants, and pyd1 seedlings grew nearly as well as wild-type seedlings with a uracil nitrogen source. These results confirm PYD1 function and suggest the possible existence of another, as yet unknown, activity for uracil degradation to dihydrouracil in this plant. * The localization of PYD-green fluorescent protein fusions in the plastid (PYD1), secretory system (PYD2) and cytosol (PYD3) suggests potentially complex metabolic regulation.
Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam OT Golm, Germany.|Leibniz-Institute of Vegetable and Ornamental Crops, 14979 Großbeeren, Germany.
Rita
R
Zrenner
Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam OT Golm, Germany.
Heike
H
Riegler
Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam OT Golm, Germany.
Cathleen R
CR
Marquard
Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam OT Golm, Germany.
Peter R
PR
Lange
Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam OT Golm, Germany.
Claudia
C
Geserick
Department of Biological Sciences, Goucher College, Baltimore, MD 21204-2794, USA.
Caren E
CE
Bartosz
Department of Biological Sciences, Goucher College, Baltimore, MD 21204-2794, USA.
Celine T
CT
Chen
Department of Biological Sciences, Goucher College, Baltimore, MD 21204-2794, USA.
Robert D
RD
Slocum
D000581:Amidohydrolases / Q000378:metabolism; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D042943:Dihydrouracil Dehydrogenase (NADP) / Q000378:metabolism; D015870:Gene Expression; D055786:Gene Knockout Techniques; D017343:Genes, Plant; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D053858:Metabolic Networks and Pathways; D009154:Mutation; D009584:Nitrogen / Q000378:metabolism*; D009711:Nucleotides / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011743:Pyrimidines / Q000378:metabolism*; D014498:Uracil / Q000378:metabolism*
D029681:Arabidopsis Proteins; D009711:Nucleotides; D011743:Pyrimidines; D049452:Green Fluorescent Proteins; D014498:Uracil; D042943:Dihydrouracil Dehydrogenase (NADP); D000581:Amidohydrolases; C021590:beta-ureidopropionase; C020047:dihydropyrimidinase; D009584:Nitrogen