Abstract
The kinetics and inhibitor specificities of phosphate transport across the plasma membrane of wheat leaf mesophyll protoplasts have been examined. Studies were also carried out on the effects of light and pH on phosphate transport and the plasma membrane electropotential. At pH 5.8 (30°C), protoplasts accumulated phosphate at the rate of 3.9 ± 0.2 nanomoles per milligram protein per hour. Phosphate uptake rates and inhibitor specificities for the leaf cell plasma membrane phosphate transporter were qualitatively similar to those observed with root protoplasts. Neither picrylsulfonic acid, or p-chloromercuribenzene sulfonate affected phosphate uptake significantly at 0.1 millimolar. Of all compounds tested, carbonyl cyanide-p-trifluoromethoxy phenylhydrazone was the most effective inhibitor of phosphate uptake (60% at 0.1 millimolar). Tribenzylphosphate inhibited uptake by 34% while dibenzylphosphate had no effect. The plasma membrane electropotential was found to be −37 ± 3 millivolts. Initiation of photosynthesis lowered the membrane potential to −39 ± 3 millivolts. Inhibition of phosphate uptake by 34% with the substrate analog tribenzylphosphate resulted in a measured membrane potential of −33 ± 3 millivolts. These changes in potential were not significant at the 5% probability level. Phosphate uptake rates remained constant under photosynthetic and nonphotosynthetic conditions. The utility of tribenzylphosphate as an inhibitor in plant systems is demonstrated.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Edwards G. E., Robinson S. P., Tyler N. J., Walker D. A. Photosynthesis by isolated protoplasts, protoplast extracts, and chloroplasts of wheat: influence of orthophosphate, pyrophosphate, and adenylates. Plant Physiol. 1978 Aug;62(2):313–319. doi: 10.1104/pp.62.2.313. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Heldt H. W., Rapley L. Specific transport of inorganic phosphate, 3-phosphoglycerate and dihydroxyacetonephosphate, and of dicarboxylates across the inner membrane of spinach chloroplasts. FEBS Lett. 1970 Oct 5;10(3):143–148. doi: 10.1016/0014-5793(70)80438-0. [DOI] [PubMed] [Google Scholar]
- Jeanjean R., Blasco F., Hirn M. Identification of a plasma membrane protein involved in Pi transport in the yeast Candida tropicalis. FEBS Lett. 1984 Jan 2;165(1):83–87. doi: 10.1016/0014-5793(84)80019-8. [DOI] [PubMed] [Google Scholar]
- Kolbe H. V., Böttrich J., Genchi G., Palmieri F., Kadenbach B. Isolation and reconstitution of the phosphate-transport system from pig heart mitochondria. FEBS Lett. 1981 Feb 23;124(2):265–269. doi: 10.1016/0014-5793(81)80152-4. [DOI] [PubMed] [Google Scholar]
- LOWRY O. H., ROSEBROUGH N. J., FARR A. L., RANDALL R. J. Protein measurement with the Folin phenol reagent. J Biol Chem. 1951 Nov;193(1):265–275. [PubMed] [Google Scholar]
- Lin W. Corn Root Protoplasts: ISOLATION AND GENERAL CHARACTERIZATION OF ION TRANSPORT . Plant Physiol. 1980 Oct;66(4):550–554. doi: 10.1104/pp.66.4.550. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lin W., Hanson J. B. Phosphate absorption rates and adenosine 5'-triphosphate concentrations in corn root tissue. Plant Physiol. 1974 Sep;54(3):250–256. doi: 10.1104/pp.54.3.250. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lin W. Responses of corn root protoplasts to exogenous reduced nicotinamide adenine dinucleotide: Oxygen consumption, ion uptake, and membrane potential. Proc Natl Acad Sci U S A. 1982 Jun;79(12):3773–3776. doi: 10.1073/pnas.79.12.3773. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lowendorf H. S., Bazinet G. F., Jr, Slayman C. W. Phosphate transport in Neurospora. Derepression of a high-affinity transport system during phosphorus starvation. Biochim Biophys Acta. 1975 May 21;389(3):541–549. doi: 10.1016/0005-2736(75)90164-9. [DOI] [PubMed] [Google Scholar]
- Rigoulet M., Guerin B. Phosphate transport and ATP synthesis in yeast mitochondria: effect of a new inhibitor: the tribenzylphosphate. FEBS Lett. 1979 Jun 1;102(1):18–22. doi: 10.1016/0014-5793(79)80919-9. [DOI] [PubMed] [Google Scholar]
- Rubinstein B. Use of lipophilic cations to measure the membrane potential of oat leaf protoplasts. Plant Physiol. 1978 Dec;62(6):927–929. doi: 10.1104/pp.62.6.927. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ullrich-Eberius C. I., Novacky A., Fischer E., Lüttge U. Relationship between Energy-dependent Phosphate Uptake and the Electrical Membrane Potential in Lemna gibba G1. Plant Physiol. 1981 Apr;67(4):797–801. doi: 10.1104/pp.67.4.797. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Wirtz W., Stitt M., Heldt H. W. Enzymic determination of metabolites in the subcellular compartments of spinach protoplasts. Plant Physiol. 1980 Jul;66(1):187–193. doi: 10.1104/pp.66.1.187. [DOI] [PMC free article] [PubMed] [Google Scholar]