Abstract
Chloroplasts were isolated from ruptured guard-cell protoplasts of the Argenteum mutant of Pisum sativum L. and purified by centrifugation through a Percoll layer. The combined volume of the intact plastids and the uptake of phosphate were determined by silicone oil-filtering centrifugation, using tritiated water and [14C]sorbitol as membrane-permeating and nonpermeating markers and [32P]phosphate as tracer for phosphate. The affinities of the phosphate translocator for organic phosphates were assessed by competition with inorganic phosphate. The affinities for dihydroxyacetone phosphate, 3-phosphoglycerate (PGA), and phosphoenolpyruvate were in the same order as those reported for mesophyll chloroplasts of several species. However, the guard-cell phosphate translocator had an affinity for glucose-6-phosphate that was as high as that for PGA. Guard-cell chloroplasts share this property with amyloplasts from the root of pea (H.W. Heldt, U.I. Flugge, S. Borchert [1991] Plant Physiol 95: 341-343). An ability to import glucose-6-phosphate enables guard-cell chloroplasts to synthesize starch despite the reported absence of a fructose-1,6-bisphosphatase activity in the plastids, which would be required if only C3 phosphates could enter through the translocator.
Full Text
The Full Text of this article is available as a PDF (1.0 MB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Fliege R., Flügge U. I., Werdan K., Heldt H. W. Specific transport of inorganic phosphate, 3-phosphoglycerate and triosephosphates across the inner membrane of the envelope in spinach chloroplasts. Biochim Biophys Acta. 1978 May 10;502(2):232–247. doi: 10.1016/0005-2728(78)90045-2. [DOI] [PubMed] [Google Scholar]
- Hedrich R., Raschke K., Stitt M. A role for fructose 2,6-bisphosphate in regulating carbohydrate metabolism in guard cells. Plant Physiol. 1985 Dec;79(4):977–982. doi: 10.1104/pp.79.4.977. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Heldt H. W., Flügge U. I., Borchert S. Diversity of specificity and function of phosphate translocators in various plastids. Plant Physiol. 1991 Feb;95(2):341–343. doi: 10.1104/pp.95.2.341. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Journet E. P., Douce R. Enzymic capacities of purified cauliflower bud plastids for lipid synthesis and carbohydrate metabolism. Plant Physiol. 1985 Oct;79(2):458–467. doi: 10.1104/pp.79.2.458. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Li Y. T. Studies on the glycosidases in jack bean meal. I. Isolation and properties of alpha-mannosidase. J Biol Chem. 1967 Dec 10;242(23):5474–5480. [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]
- Zeiger E., Armond P., Melis A. Fluorescence Properties of Guard Cell Chloroplasts: EVIDENCE FOR LINEAR ELECTRON TRANSPORT AND LIGHT-HARVESTING PIGMENTS OF PHOTOSYSTEMS I AND II. Plant Physiol. 1981 Jan;67(1):17–20. doi: 10.1104/pp.67.1.17. [DOI] [PMC free article] [PubMed] [Google Scholar]