Institute for Plant Sciences of Montpellier (IPSiM)

Ion Flux Coordination and signaling in plant cells (INFLUX)

Group leader: Alexis De Angeli
Senior Scientist CNRS

Key words

Stomata, electrophysiology,  biosensor, cell imaging, ion transport

Presentation

The aim of the group is to understand the molecular mechanisms involved in the regulation and coordination of ion fluxes across the cellular membranes of plant cells. To have coherent cellular responses to environmental stimuli the events occurring in the different cellular membranes of eukaryotic cells need to be coordinated.  In plants, stomata are illustrative of the importance of the control of ion fluxes in cells. Stomata are plant specific structures forming pores at the surface of leaves controlling the gas exchanges with the atmosphere.  The stomata pore aperture controls CO₂ uptake and water loss by evaporation and consequently contributes to biomass production and drought tolerance in land plants. The stomata pore is delimited by two specialized cells, the guard cells, controlling its aperture. The control of the stomata pore depends on the capacity of guard cells to induce massive and controlled ion fluxes across the plasma and the vacuolar membranes to change their volume and consequently the stomata aperture.

In plant cells, similarly to other eukaryotic cells, ion transport is fundamental in signaling cascades, in regulating transmembrane potential and intracellular ion concentrations (e.g. Cl–, NO3–, malate2-, K+, Ca2+ and H+). Further, ion transport in also involved in mineral nutrition and in the maintenance of the turgor pressure. Cellular responses involving ion fluxes rely on the coordination of the transport reactions occurring in the cellular membranes.   

To unravel the mechanisms underlying the coordination of the events occurring in the different plant cell membranes we use different approaches. We investigate the mechanisms of ion fluxes coordination from the biophysical properties of ion channels, to their function within the cell and their role at a whole plant level. We specifically focus on the ion channels of the ALMT (Aluminum activated Malate Transporters) family that plays an important role in stomata functioning. We investigate the molecular basis of the regulation of the ALMTs (ion selectivity, activation by malate and nucleotide block, secondary modifications) and its impact in plant cells. Because guard cells are an ideal paradigm to study flux coordination and they are important for plant adaptation to the environment we use this cell type as a model for our study.

To achieve our goal we use and develop different experimental approaches:

• electrophysiology (patch-clamp, TEVC) to understand the molecular properties (transport reactions and regulation) of ion transporters of the vacuolar and plasma membrane.
• live cell imaging coupled to genetically encoded fluorescent biosensors to visualize the dynamic of intracellular ionic concentrations (e.g. NO3–, Cl– and H+) and the in vivo activity of ion transporters.
• physiology and genetics
• mathematical models