Abstract text:      When plants are exposed to strong hyperosmotic stress, water exits the cell leading to plasmolysis, where the plasma membrane detaches partially from the cell wall. This detachment reveals discrete sites, where the plasma membrane remains connected to the wall. To identify the molecular components underlying this physical linkage, we conducted a targeted screen of Arabidopsis candidate proteins (Fig 1). Among them, overexpression of the receptor-like kinase LecRK-I.9 significantly increased the density of plasma membrane–wall connections in Nicotiana benthamiana pavement cells. We found that the extracellular lectin domain of LecRK-I.9 is required for establishing these connections. Under hyperosmotic conditions, LecRK-I.9 forms immobile clusters, exhibiting an asymmetric distribution across cell surfaces in the epidermis of different organs in Arabidopsis. Deletion of the lectin domain increases cluster mobility and abolishes this asymmetry, indicating that the lectin domain regulates LecRK-I.9 spatial organization at the plasma membrane (Fig 2).
     We are currently determining whether the lectin domain binds to specific microdomains within the wall, and assessing whether LecRK-I.9 overexpression modulates wall deformation during hyperosmotic stress. We are also evaluating the tolerance of LecRK-I.9 overexpressing lines to low water potential and drought conditions that challenge the integrity of the plasma membrane–wall continuum.