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Mechanosensitive channels are activated by stress in the actin stress fibres, and could be involved in gravity sensing in plants
Author(s) -
Tatsumi H.,
Furuichi T.,
Nakano M.,
Toyota M.,
Hayakawa K.,
Sokabe M.,
Iida H.
Publication year - 2014
Publication title -
plant biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.871
H-Index - 87
eISSN - 1438-8677
pISSN - 1435-8603
DOI - 10.1111/plb.12095
Subject(s) - mechanosensitive channels , cytoskeleton , actin cytoskeleton , actin , biology , biophysics , microbiology and biotechnology , optical tweezers , amyloplast , ion channel , cell , biochemistry , physics , receptor , plastid , chloroplast , quantum mechanics , gene
Mechanosensitive ( MS ) channels are expressed in a variety of cells. The molecular and biophysical mechanism involved in the regulation of MS channel activities is a central interest in basic biology. MS channels are thought to play crucial roles in gravity sensing in plant cells. To date, two mechanisms have been proposed for MS channel activation. One is that tension development in the lipid bilayer directly activates MS channels. The second mechanism proposes that the cytoskeleton is involved in the channel activation, because MS channel activities are modulated by pharmacological treatments that affect the cytoskeleton. We tested whether tension in the cytoskeleton activates MS channels. Mammalian endothelial cells were microinjected with phalloidin‐conjugated beads, which bound to stress fibres, and a traction force to the actin cytoskeleton was applied by dragging the beads with optical tweezers. MS channels were activated when the force was applied, demonstrating that a sub‐p N force to the actin filaments activates a single MS channel. Plants may use a similar molecular mechanism in gravity sensing, since the cytoplasmic C a 2+ concentration increase induced by changes in the gravity vector was attenuated by potential MS channel inhibitors, and by actin‐disrupting drugs. These results support the idea that the tension increase in actin filaments by gravity‐dependent sedimentation of amyloplasts activates MS C a 2+ ‐permeable channels, which can be the molecular mechanism of a C a 2+ concentration increase through gravistimulation. We review recent progress in the study of tension sensing by actin filaments and MS channels using advanced biophysical methods, and discuss their possible roles in gravisensing.

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