title: A nitrate-permeable ion channel in the tonoplast of the moss Physcomitrella patens.
abstract: In this work, for the first time the activity of nitrate-permeable channels in the tonoplast of the moss Physcomitrella patens was recorded. The channels allowed nitrate flow in one direction-from the cytoplasm to the vacuole. Selectivity of nitrate over chloride of the channels was proved. The activity of the channels was dependent on cytoplasmic calcium, magnesium, and pH. A patch-clamp study carried out on the vacuolar membrane of the moss Physcomitrella patens has revealed that inhibition of cation-selective channels leads to disclosure of channels permeable to NO3 (-). These channels were inwardly rectifying and allowed anions to flow from the cytoplasm to the vacuole. After a decrease in the cytoplasmic NO3 (-) concentration, the current density recorded in the whole-vacuole configuration and amplitude of the currents flowing through single channels were reduced. Application of the NO3 (-) gradient caused a shift in the reversal potential (Erev) towards ENO3-, indicating NO3 (-) permeability. Research of the selectivity of the channels to Cl(-) and NO3 (-) was also done; it indicated that Cl(-) is less permeable than NO3 (-) (PNO3/PCl = 3.08). Measurements with different concentrations of cytoplasmic Ca(2+) and Mg(2+) revealed that the channel was activated by different concentrations of these ions-100 µM Ca(2+) and 10 mM Mg(2+). Calcium dependence of the channels was also modulated by a redox agent-DTT (dithiothreitol), which added on the cytoplasmic side, caused a reduction in the threshold of channel activation with cytoplasmic Ca(2+). The NO3 (-) permeable channel was also pH dependent. A decrease in the cytoplasmic pH reduced the open probability of the channel; in turn, an increase in the vacuolar pH did not decrease ion channel activity but lowered its conductance.
authors: Department of Biophysics, Institute of Biology and Biochemistry, Maria Curie-Skłodowska University, Akademicka 19, 20-033, Lublin, Poland, mateusz.koselski@poczta.umcs.lublin.pl.
authors: Mateusz
authors: M
authors: Koselski
authors: Halina
authors: H
authors: Dziubinska
authors: Aleksandra
authors: A
authors: Seta-Koselska
authors: Kazimierz
authors: K
authors: Trebacz
mesh_terms: D019068:Bryopsida; D007473:Ion Channels / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism*; D015388:Organelles / Q000378:metabolism*; D018408:Patch-Clamp Techniques
chemical_list: D007473:Ion Channels; D009566:Nitrates
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