KINPLANTS

Regulation of inward K+ channel activity in Arabidopsis by the Shaker subunit AtKC1: molecular mechanisms and role in control of stomatal opening and plant adaptation to water stress

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 Obiettivo del progetto (Objective)

'Plant Shaker channels form the major K conductance of the plasma membrane, thereby mediating large K fluxes required for plant growth and development. Also, owing to the role of K ion in control of the cell osmotic potential, they are involved in the modulation of stomatal movements, which is necessary for allowing CO2 uptake while limiting transpirational water loss. Thus, they contribute to plant adaptation to changes in water availability and air humidity. Shaker channels are homo- or heterotetramers associating 4 Shaker subunits. In the model plant Arabidopsis, the Shaker subunit AtKC1 is not able to form a functional homotetrameric channel at the plasma membrane. Instead, it is retained in the endoplasmic reticulum (ER). However, when co-expressed with other Shaker subunits, it forms heteromeric channels targeted to the plasma membrane and endowed with new functional properties. Thus, AtKC1 behaves as a silent regulatory subunit. The atkc1 mutant displays a remarkable and pleiotropic phenotype, including reduced growth and impaired stomatal control leading to increased transpirational water loss. The project proposes an integrated approach associating molecular, biochemical and biophysical approaches, along with cell biology and whole plant physiology, in order to unravel the role that AtKC1 plays in stomatal regulation and adaptation to water stress. Different aspects will be investigated: the molecular determinants of AtKC1 activity (for instance, regulatory partner proteins), and physiological impacts of AtKC1 activity on whole plant and guard cell physiology under different environmental and hormonal conditions. Physiological aspects will be studied in wild type and atkc1 KO mutant plants, using the Phenopsis phenotyping platform for whole plant transpiration measurements and electrophysiology techniques for measuring K channel activity and membrane potential changes in epidermal and guard cells.'

Descrizione progetto (Article)

Shaker channels are membrane proteins in plant cells that control the transfer of potassium (K) ions into the cell. This in turn helps control the flow of water through the plant. It has been proved that these channels play a role in the opening and closing of stomata (leaf pores that regulate transpiration) through this process.

The EU-funded KINPLANTS project aimed to elucidate the role of AtKC1 (one of the sub-units that make up the Shaker channel protein) in stomatal control. Researchers conducted physiological studies of whole plant transpiration and molecular studies of AtKC1 in different plant cell types. Both approaches relied on the use of modified Arabidopsis thaliana plants that do not produce the AtKC1 sub-unit or produced it only in certain cellular types.

Research revealed that AtKC1 is a key player in the functioning of Shaker channels. Without the AtKC1 sub-unit, plants grew more slowly and were unable to control transpiration effectively.

Another major finding was that AtKC1 exerts control of stomatal cells known as guard cells by changing the osmotic potential of nearby epidermal (surface) cells. Without functional AtKC1 in these adjacent cells, the guard cells could not effectively control stomatal opening and closing.

The work of KINPLANTS has unearthed a major molecular controller of transpiration in epidermal cells for the first time. This provides researchers with an attractive target for engineering better water use efficiency in crop plants.