Abstract
Stomatal opening in response to light has a component that matches the absorption spectrum of chlorophyll; however, the intervening sensory transduction steps are not well understood. To study this process, we illuminated Vicia faba guard cell protoplasts with red light and simultaneously recorded current flow across the plasma membrane, utilizing the patch clamp technique in the whole cell configuration. We report evidence that under voltage clamp conditions, red light (1 mmol of photons.m-2.S-1) stimulated an outward current. This response required ATP (2.5 mM) and orthophosphate (1 mM) at the cytoplasmic side of the membrane. Both red-light-stimulated currents and currents activated in the dark by the proton pump agonist fusicoccin (10 microM) were abolished by the protonophore carbonylcyanide m-chlorophenylhydrazone at 10 microM, indicating that these responses were carried by protons. Pump currents were inhibited by orthovanadate applied to the cytoplasmic side of the membrane (50% inhibition at 3.5 microM), implicating a H+ -ATPase. Elimination of the current by the photosynthetic inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea, in the presence of saturating concentrations of ATP, pointed to a requirement for photosynthetically active chloroplasts. We conclude that red light stimulates an electrogenic proton pump at the plasmalemma of Vicia guard cells and that chloroplasts modulate this response.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Bowman B. J., Slayman C. W. The effects of vanadate on the plasma membrane ATPase of Neurospora crassa. J Biol Chem. 1979 Apr 25;254(8):2928–2934. [PubMed] [Google Scholar]
- Hamill O. P., Marty A., Neher E., Sakmann B., Sigworth F. J. Improved patch-clamp techniques for high-resolution current recording from cells and cell-free membrane patches. Pflugers Arch. 1981 Aug;391(2):85–100. doi: 10.1007/BF00656997. [DOI] [PubMed] [Google Scholar]
- Sanders D., Hansen U. P., Slayman C. L. Role of the plasma membrane proton pump in pH regulation in non-animal cells. Proc Natl Acad Sci U S A. 1981 Sep;78(9):5903–5907. doi: 10.1073/pnas.78.9.5903. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Schroeder J. I., Raschke K., Neher E. Voltage dependence of K channels in guard-cell protoplasts. Proc Natl Acad Sci U S A. 1987 Jun;84(12):4108–4112. doi: 10.1073/pnas.84.12.4108. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Shimazaki K., Zeiger E. Cyclic and Noncyclic Photophosphorylation in Isolated Guard Cell Chloroplasts from Vicia faba L. Plant Physiol. 1985 Jun;78(2):211–214. doi: 10.1104/pp.78.2.211. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Shimazaki K., Zeiger E. Red Light-Dependent CO(2) Uptake and Oxygen Evolution in Guard Cell Protoplasts of Vicia faba L.: Evidence for Photosynthetic CO(2) Fixation. Plant Physiol. 1987 May;84(1):7–9. doi: 10.1104/pp.84.1.7. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Spanswick R. M. Evidence for an electrogenic ion pump in Nitella translucens. I. The effects of pH, K + , Na + , light and temperature on the membrane potential and resistance. Biochim Biophys Acta. 1972 Oct 23;288(1):73–89. doi: 10.1016/0005-2736(72)90224-6. [DOI] [PubMed] [Google Scholar]