title: Hyperpolarization-activated Ca2+-permeable channels in the plasma membrane of tomato cells.
abstract: The hyperpolarization of the electrical plasma membrane potential difference has been identified as an early response of plant cells to various signals including fungal elicitors. The hyperpolarization-activated influx of Ca2+ into tomato cells was examined by the application of conventional patch clamp techniques. In both whole cell and single-channel recordings, clamped membrane voltages more negative than -120 mV resulted in time- and voltage-dependent current activation. Single-channel currents saturated with increasing activities of Ca2+ and Ba2+ from 3 to 26 mm and the single channel conductance increased from 4 pS to 11 pS in the presence of 20 mm Ca2+ or Ba2+, respectively. These channels were 20-25 and 10-13 times more permeable to Ca2+ than to K+ and to Cl-, respectively. Channel currents were strongly inhibited by 10 microM lanthanum and 50% inhibited by 100 microM nifedipine. This evidence suggests that hyperpolarization-activated Ca2+-permeable channels provide a mechanism for the influx of Ca2+ into tomato cells.
authors.affiliation: Department of Botany, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada M5S 3B2.
authors.forename: A
authors.initials: A
authors.lastname: Gelli
authors.forename: E
authors.initials: E
authors.lastname: Blumwald
mesh_terms: D001464:Barium / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology*; D002462:Cell Membrane / Q000502:physiology; D007811:Lanthanum / Q000494:pharmacology; D018551:Solanum lycopersicum / Q000502:physiology*; D008564:Membrane Potentials; D018408:Patch-Clamp Techniques; D011523:Protoplasts / Q000502:physiology*; D015398:Signal Transduction
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D001464:Barium; D007811:Lanthanum; D002118:Calcium