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Mechanosensory calcium‐selective cation channels in epidermal cells
Author(s) -
Ding Jiu Ping,
Pickard Barbara G.
Publication year - 1993
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.1993.t01-4-00999.x
Subject(s) - mechanosensitive channels , biology , biophysics , cytoskeleton , guard cell , microbiology and biotechnology , transmembrane protein , extracellular , cytosol , ion channel , biochemistry , cell , enzyme , receptor
Summary This paper explores the properties and likely functions of an epidermal Ca 2+ ‐selective cation channel complex activated by tension. As many as eight or nine linked or linkable equivalent conductance units or co‐channels can open together. Open time for co‐channel quadruplets and quintuplets tends to be relatively long with millimolar Mg 2+ (but not millimolar Ca 2+ ) at the cytosolic face of excised plasma membrane. Sensitivity to tension is regulated by transmembrane voltage and temperature. Under some circumstances channel activity is synchronized in rhythmic pulses. Certain lanthanides and a cytoskeleton‐disturbing herbicide that inhibit gravitropic reception act on the channel system at low concentrations. Specifically, ethyl‐ N ‐phenylcarbamate promotes tension‐dependent activity at micromolar levels. With moderate suction, Gd 3+ provided at about 0.5 μM at the extracellular face of the membrane promotes for several seconds but may then become inhibitory. Provision at 1–2 μM promotes and subsequently inhibits more vigorously (often abruptly and totally), and at high levels inhibits immediately. La 3+ , a poor gravitropic inhibitor, acts similarly but much more gradually and only at much higher concentrations. These properties, particularly these susceptibilities to modulation, indicate that in vivo the mechanosensitive channel must be mechano‐sensory and mechanoregulatory. It could serve to transduce the shear forces generated in the integrated wall‐membrane‐cytoskeleton system during turgor changes and cell expansion as well as transducing the stresses induced by gravity, touch and flexure. In so far as such transduction is modulated by voltage and temperature, the channels would also be sensors for these modalities as long as the wall‐membrane‐cytoskeleton system experiences mechanical stress.