title: Adenylate gradients and Ar:O(2) effects on legume nodules: I. Mathematical models.
abstract: Mathematical models were developed to test the likelihood that large cytosolic adenylate concentration gradients exist across the bacteria-infected cells of legume nodules. Previous studies hypothesized that this may be the case to account for the unusually low adenylate energy charge (AEC; 0.65) measured in the plant fraction of metabolically active nodules (M.M. Kuzma, H. Winter, P. Storer, I. Oresnik, C.A. Atkins, D.B. Layzell [1999] Plant Physiol 119: 399-407). Simulations coupled leghemoglobin-facilitated O(2) diffusion into the infected cell, through bacteroid nitrogenase activity, with the ATP demand for transport and ammonia assimilation in the plant fraction of ureide- and amide-producing nodules. Although large cytosolic adenylate gradients were predicted to exist in both nodule types, amide nodules were predicted to have steeper AEC gradients (0.82-0.52) than ureide nodules (0.82-0.61). The differences were attributed to an additional ATP demand for Asn synthesis in the amide nodule. Simulations for nodules transferred to an Ar:O(2) atmosphere predicted a major reduction in the magnitude of adenylate gradients and an increase in the AEC of the plant fraction. Results were consistent with a number of experimental studies and were used to propose an experimental test of the models.
authors.affiliation: Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6.
authors.forename: Hui
authors.initials: H
authors.lastname: Wei
authors.forename: Craig A
authors.initials: CA
authors.lastname: Atkins
authors.forename: David B
authors.initials: DB
authors.lastname: Layzell
mesh_terms: D000249:Adenosine Monophosphate / Q000737:chemistry / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000641:Ammonia / Q000378:metabolism; D001128:Argon / Q000494:pharmacology*; D001419:Bacteria / Q000254:growth & development; D001692:Biological Transport / Q000502:physiology; D003600:Cytosol / Q000378:metabolism; D004058:Diffusion / Q000187:drug effects; D007887:Fabaceae / Q000187:drug effects / Q000254:growth & development* / Q000382:microbiology; D007874:Leghemoglobin / Q000378:metabolism; D008954:Models, Biological; D009591:Nitrogenase / Q000378:metabolism; D010100:Oxygen / Q000494:pharmacology*; D010101:Oxygen Consumption / Q000187:drug effects / Q000502:physiology; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development* / Q000382:microbiology
chemical_list: D007874:Leghemoglobin; D000249:Adenosine Monophosphate; D001128:Argon; D000641:Ammonia; D000255:Adenosine Triphosphate; D009591:Nitrogenase; D010100:Oxygen