Abstract
42K+ and 86Rb+ were used to determine the subcellular distribution of potassium in Chlamydomonas reinhardtii by compartmental analysis. In both wild type and a mutant strain, three distinct compartments (referred to as I, II, and III) were apparent. Using 42K+, we found that these had half-lives for K+ exchange of 1.07 min, 12.8 min, and 2.9 h, respectively, in wild-type cells and 0.93 min, 14.7 min, and 9.8 h, respectively, for the mutants. Half-lives were not significantly different when 86Rb+ was used to trace K+. Compartments I and II probably correspond to the cell wall and cytoplasm, respectively. Based on the lack of a large central vacuole in Chlamydomonas, the effect of a dark pretreatment on the kinetic properties of compartment III and the similarity between the [K+] of compartment III and that of isolated chloroplasts, this slowly exchanging compartment was identified as the chloroplast. Growth of wild-type cells at 100 [mu]M (instead of 10 mM K+) caused no change of cytoplasmic [K+] but reduced chloroplast [K+] very substantially. The mutants failed to grow at 100 [mu]M K+.
Full Text
The Full Text of this article is available as a PDF (890.8 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Barber J. Measurement of the membrane potential and evidence for active transport of ions in Chlorella pyrenoidosa. Biochim Biophys Acta. 1968 Jun 11;150(4):618–625. doi: 10.1016/0005-2736(68)90051-5. [DOI] [PubMed] [Google Scholar]
- Demmig B., Gimmler H. Properties of the Isolated Intact Chloroplast at Cytoplasmic K Concentrations : I. Light-Induced Cation Uptake into Intact Chloroplasts is Driven by an Electrical Potential Difference. Plant Physiol. 1983 Sep;73(1):169–174. doi: 10.1104/pp.73.1.169. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Mason C. B., Matthews S., Bricker T. M., Moroney J. V. Simplified Procedure for the Isolation of Intact Chloroplasts from Chlamydomonas reinhardtii. Plant Physiol. 1991 Dec;97(4):1576–1580. doi: 10.1104/pp.97.4.1576. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Maury W. J., Huber S. C., Moreland D. E. Effects of Magnesium on Intact Chloroplasts : II. CATION SPECIFICITY AND INVOLVEMENT OF THE ENVELOPE ATPase IN (SODIUM) POTASSIUM/PROTON EXCHANGE ACROSS THE ENVELOPE. Plant Physiol. 1981 Dec;68(6):1257–1263. doi: 10.1104/pp.68.6.1257. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Pier P. A., Berkowitz G. A. Modulation of water stress effects on photosynthesis by altered leaf k. Plant Physiol. 1987 Nov;85(3):655–661. doi: 10.1104/pp.85.3.655. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Pitman M. G., Läuchli A., Stelzer R. Ion distribution in roots of barley seedlings measured by electron probe x-ray microanalysis. Plant Physiol. 1981 Sep;68(3):673–679. doi: 10.1104/pp.68.3.673. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Robinson S. P., Downton W. J. Potassium, sodium, and chloride content of isolated intact chloroplasts in relation to ionic compartmentation in leaves. Arch Biochem Biophys. 1984 Jan;228(1):197–206. doi: 10.1016/0003-9861(84)90061-4. [DOI] [PubMed] [Google Scholar]
- Rygiewicz P. T., Bledsoe C. S., Glass A. D. A comparison of methods for determining compartmental analysis parameters. Plant Physiol. 1984 Dec;76(4):913–917. doi: 10.1104/pp.76.4.913. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Wu W., Berkowitz G. A. Stromal pH and Photosynthesis Are Affected by Electroneutral K and H Exchange through Chloroplast Envelope Ion Channels. Plant Physiol. 1992 Feb;98(2):666–672. doi: 10.1104/pp.98.2.666. [DOI] [PMC free article] [PubMed] [Google Scholar]