A Mechanosensitive Channel in Whole Cells and in Membrane Patches of the Fungus Uromyces

Bean leaf stomata provide a topographical signal that induces germlings of the phytopathogen Uromyces appendiculatus to develop specialized infection structures. Protoplasts from germ tubes of this fungus, when examined with patch-clamp electrodes, displayed the activities of a 600-picosiemen mechanosensitive ion channel. This channel passes a variety of cations, including Ca$^{2+}$, and is blocked by Gd$^{3+}$ at 50 micromolar. This channel could transduce the membrane stress induced by the leaf topography into an influx of ions, including Ca$^{2+}$, that may trigger differentiation.