Abstract
In vivo 15N NMR spectroscopy was used to monitor the assimilation of ammonium by cell-suspension cultures of carrot (Daucus carota L. cv Chantenay). The cell suspensions were supplied with oxygen in the form of either pure oxygen ("oxygenated cells") or air ("aerated cells"). In contrast to oxygenated cells, in which ammonium assimilation had no effect on cytoplasmic pH, ammonium assimilation by aerated cells caused a decrease in cytoplasmic pH of almost 0.2 pH unit. This led to a change in nitrogen metabolism resulting in the accumulation of [gamma]-aminobutyric acid. The metabolic effect of the reduced oxygen supply under aerated conditions could be mimicked by artificially decreasing the cytoplasmic pH of oxygenated cells and was abolished by increasing the cytoplasmic pH of aerated cells. The activity of glutamate decarboxylase increased as the cytoplasmic pH declined and decreased as the pH recovered. These findings are consistent with a role for the decarboxylation of glutamate, a proton-consuming reaction, in the short-term regulation of cytoplasmic pH, and they demonstrate that cytoplasmic pH influences the pathways of intermediary nitrogen metabolism.
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- Bradford M. M. A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal Biochem. 1976 May 7;72:248–254. doi: 10.1006/abio.1976.9999. [DOI] [PubMed] [Google Scholar]
- Carroll A. D., Stewart G. R., Phillips R. Dynamics of Nitrogenous Assimilate Partitioning between Cytoplasmic and Vacuolar Fractions in Carrot Cell Suspension Cultures. Plant Physiol. 1992 Dec;100(4):1808–1814. doi: 10.1104/pp.100.4.1808. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Crawford L. A., Bown A. W., Breitkreuz K. E., Guinel F. C. The Synthesis of [gamma]-Aminobutyric Acid in Response to Treatments Reducing Cytosolic pH. Plant Physiol. 1994 Mar;104(3):865–871. doi: 10.1104/pp.104.3.865. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Fox G. G., Ratcliffe G. P NMR Observations on the Effect of the External pH on the Intracellular pH Values in Plant Cell Suspension Cultures. Plant Physiol. 1990 Jun;93(2):512–521. doi: 10.1104/pp.93.2.512. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Franchi A., Cragoe E., Jr, Pouysségur J. Isolation and properties of fibroblast mutants overexpressing an altered Na+/H+ antiporter. J Biol Chem. 1986 Nov 5;261(31):14614–14620. [PubMed] [Google Scholar]
- Lane T. R., Stiller M. Glutamic acid decarboxylation in Chlorella. Plant Physiol. 1970 May;45(5):558–562. doi: 10.1104/pp.45.5.558. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Mayer R. R., Cherry J. H., Rhodes D. Effects of heat shock on amino Acid metabolism of cowpea cells. Plant Physiol. 1990 Oct;94(2):796–810. doi: 10.1104/pp.94.2.796. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Menegus F., Cattaruzza L., Chersi A., Fronza G. Differences in the Anaerobic Lactate-Succinate Production and in the Changes of Cell Sap pH for Plants with High and Low Resistance to Anoxia. Plant Physiol. 1989 May;90(1):29–32. doi: 10.1104/pp.90.1.29. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Murphy T. M., Matson G. B., Morrison S. L. Ultraviolet-Stimulated KHCO(3) Efflux from Rose Cells: Regulation of Cytoplasmic pH. Plant Physiol. 1983 Sep;73(1):20–24. doi: 10.1104/pp.73.1.20. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Robinson S. A., Slade A. P., Fox G. G., Phillips R., Ratcliffe R. G., Stewart G. R. The role of glutamate dehydrogenase in plant nitrogen metabolism. Plant Physiol. 1991 Feb;95(2):509–516. doi: 10.1104/pp.95.2.509. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Snedden W. A., Chung I., Pauls R. H., Bown A. W. Proton/l-Glutamate Symport and the Regulation of Intracellular pH in Isolated Mesophyll Cells. Plant Physiol. 1992 Jun;99(2):665–671. doi: 10.1104/pp.99.2.665. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Wallace W., Secor J., Schrader L. E. Rapid Accumulation of gamma-Aminobutyric Acid and Alanine in Soybean Leaves in Response to an Abrupt Transfer to Lower Temperature, Darkness, or Mechanical Manipulation. Plant Physiol. 1984 May;75(1):170–175. doi: 10.1104/pp.75.1.170. [DOI] [PMC free article] [PubMed] [Google Scholar]