Two MscS Homologs Provide Mechanosensitive Channel Activities in the Arabidopsis Root

In bacterial and animal systems, mechanosensitive (MS) ion channels are thought to mediate the perception of pressure, touch, and sound 1, 2 and 3. Although plants respond to a wide variety of mechanical stimuli, and although many mechanosensitive channel activities have been characterized in plant membranes by the patch-clamp method, the molecular nature of mechanoperception in plant systems has remained elusive [4]. Likely candidates are relatives of MscS (Mechanosensitive channel of small conductance), a well-characterized MS channel that serves to protect E. coli from osmotic shock [5]. Ten MscS-Like (MSL) proteins are found in the genome of the model flowering plant Arabidopsis thaliana 4, 6 and 7. MSL2 and MSL3, along with MSC1, a MscS family member from green algae, are implicated in the control of organelle morphology 8 and 9. Here, we characterize MSL9 and MSL10, two MSL proteins found in the plasma membrane of root cells. We use a combined genetic and electrophysiological approach to show that MSL9 and MSL10, along with three other members of the MSL family, are required for MS channel activities detected in protoplasts derived from root cells. This is the first molecular identification and characterization of MS channels in plant membranes

Traumatismes, ondes electrophysiologiques et induction a distance de correlations entre organes chez Bidens pilosus L

SIGLECNRS T 57503 (1-2) / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Les canaux anioniques de la membrane plasmique chez Arabidopsis thaliana (caractérisation fonctionnelle et mise en place d'outils pour l'identification moléculaire)

PARIS-BIUSJ-Thèses (751052125) / SudocCentre Technique Livre Ens. Sup. (774682301) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Sensing forces in plants with mechanosensitive channels

International audiencePlant as all living organisms are subjected to mechanical forces arising either from their environment or from inside their own body. From the environment mechanical cue are present through obstacles in the soil encountered by root or through rain wind and gravity exerting mechanical stimulations on aerial parts. From inside, forces result from the high osmotic pressure encountered in the cell and at shoot scale from the compression of inner tissues whilst outer tissues are under tension. To probe these forces, in order to control their development, organisms have develop very efficient mechanosensors: the mechanosensitive (MS) channels

Ion channels in mechanosensing and electrical signaling in plants

Plants as animals have cell membrane equipped with ion channels. These channels embedded in the membrane allowed ion to move in or out the cell. Therefore these proteins are involved in several physiological processes such as nutrition, sensing (of environmental factors) and long-distance communication. In this “slide presentation” we report the possible role of ion channels in sensing oscillation and in long distance signalling in plant. The first example concerns the mechanosensitive channels of the MSL (Mechanosensitive channel Small conductance-Like) family and illustrate how it possibly behave as an oscillation sensor for the plant. The function of such a channel is consistent with the capacity of terrestrial plants to react to repetitive mechanical load produced by wind. The second example concerns the role of mechano-gated and voltage-gated channels in the generation and long distance propagation of electrical signal in plant. More precisely, it illustrate how Action Potential and Slow Wave of depolarization are generated and propagate along plant tissues. Eventually the relevance of such electrical signals in plant is illustrated by two examples

Ion channels in mechanosensing and electrical signaling in plants

Plants as animals have cell membrane equipped with ion channels. These channels embedded in the membrane allowed ion to move in or out the cell. Therefore these proteins are involved in several physiological processes such as nutrition, sensing (of environmental factors) and long-distance communication. In this “slide presentation” we report the possible role of ion channels in sensing oscillation and in long distance signalling in plant. The first example concerns the mechanosensitive channels of the MSL (Mechanosensitive channel Small conductance-Like) family and illustrate how it possibly behave as an oscillation sensor for the plant. The function of such a channel is consistent with the capacity of terrestrial plants to react to repetitive mechanical load produced by wind. The second example concerns the role of mechano-gated and voltage-gated channels in the generation and long distance propagation of electrical signal in plant. More precisely, it illustrate how Action Potential and Slow Wave of depolarization are generated and propagate along plant tissues. Eventually the relevance of such electrical signals in plant is illustrated by two examples

Du canal dépendant du voltage AtVDAC-1 à l'identification de deux canaux mécano-sensibles MSL9 et MSL10 sur la membrane plasmique d'arabidopsis thaliana

Les travaux présentés dans ce documents caractérisent l activité de trois canaux ioniques. La protéine AtVDAC-1, une VDAC (Voltage Dependent Anion Channel) atypique de par sa double localisation mitochondrie/membrane plasmique est étudiée en système artificiel. Nous montrons qu elle forme un canal possédant les grandes caractéristiques biophysiques des VDAC avec cependant quelques singularités comme par exemple une sensibilité au voltage asymétrique et décalée. Les recherches de cette activité en système homologue, sur la membrane de protoplastes racinaires d Arabidopsis thaliana, nous ont conduit à la mise en évidence d une activité mécano-sensible (MS). Sa caractérisation fait l objet de la seconde partie de ce document. Suite à l analyse réalisée en patch-clamp de différents mutants et de l expression transitoire de gènes candidats en système homologue nous identifions les protéines MSL9 et MSL10 ( Mechanosensitive channel of Small conductance Like), comme étant deux canaux MS. Ces deux protéines, homologues du canal bactérien MscS (Mechanosensitive channel of Small conductance), s activent en réponse à une augmentation de la tension de membrane et présentent des conductances distinctes. Nos travaux montrent que ces canaux sont perméants aux ions chlorure et nitrate et non aux ions calcium. Nous suggérons que l activité MS dominante sur les protoplastes racinaires de plantules de génotype sauvage résulte du fonctionnement en complexe de ces deux protéines . MSL9 et MSL10 sont les premiers canaux MS identifiés génétiquement et fonctionnellement sur une plante supérieure.The activities of three ion channels were characterized in this thesis. AtVDAC-1, a voltage Dependent Anion Channel an unusual localization, both in mitochondria and in the plasma membrane, was studied in an artificial system. It forms a channel with biophysical features of VDAC with some peculiarities like a nonsymetrical voltage dependency. Searching for the AtVDAC-1 activity on the membrane of root protoplasts from Arabidopsis thaliana led to the identification of a mechanosensitive activity. Its characterization is the subject of the second part of this document. Different mutants and candidate genes transiently expressed in homologous system were analysed using the patch-clamp technique. From the experiments, the proteins named MSL9 and MSL10 (Mechanosensitive channel of Small conductance Like) are identified as two mechanosensitive channels. These two proteins, homologs of the bacterial MscS (Mechano Sensitive channel of Small conductance), are activated in reponse to an increase in membrane tension and have distinct conductances. Our experiments showed that these channels are permeant for chloride and nitrate ions and not for calcium. We suggest that the main mechanosensitive activity in root protoplasts of wild-type mechanosensitive channels functionally and genetically identified in higher plants.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Calcium and plasma membrane force-gated ion channels behind development

International audienceDuring development, tissues are submitted to high variation of compression and tension forces. The roles of the cell wall, the cytoskeleton, the turgor pressure and the cell geometry during this process have received due attention. In contrast, apart from its role in the establishment of turgor pressure, the involvement of the plasma membrane as a transducer of mechanical forces during development has been under studied. Force-gated (FG) or Mechanosensitive (MS) ion channels embedded in the bilayer represent 'per se' archetypal mechanosensor able to directly and instantaneously transduce membrane forces into electrical and calcium signals. We discuss here how their fine-tuning, combined with their ability to detect micro-curvature and local membrane tension, allows FG channels to transduce mechanical cues into developmental signals