Aquaporins in Beta vulgaris: root hydraulic adjustment under salt stress

VICTORIA VITALI; AMODEO, GABRIELA; MOIRA SUTKA

Vancouver

Workshop; The 6th PanAmerican Plant Membrane Biology Workshop; 2018

The analysis of plant hydraulic properties needs to integrate recent advances at the molecular level and in this context to highlight the properties of biological membranes at the cell-to-cell pathway. In our working model -the halotolerant Beta vulgaris- we confirmed: i) a highly permeable cell-to-cell pathway (an isolated fraction of root Beta vulgaris plasma membrane vesicles shows water plasma membrane permeability ~ 500 µm s-1) and ii) highly regulated plasmamembrane aquaporins -BvPIP2;1, BvPIP2;2 and BvPIP1;1- in terms of trafficking and gating. Our working hypothesis is that Beta vulgaris root hydraulic adjustment capacity to cope with salt stress is favored by the adjustment capacity of the cell-to-cell pathway. Therefore we characterized the root hydraulic conductivity (Lp) in hydroponically-grown seedlings by: a) screening the short-term response to increasing salt concentrations (0 - 200mM), b) testing the effect of inhibitory compounds and c) discriminating the apoplast/cell-to-cell pathway. Our results show that Beta vulgaris root Lp response to a short-term salt treatment reflects a bimodal pattern, showing capacity to maintain water flow as well as to dramatically reduce it. While the apoplast contribution is limited, the cell-to-cell pathway activity seems to be crucial in maintaining the water flow, suggesting its highly regulated capacity is allowing to exert short-term adjustments on the actual water flow. We propose an alternative topology of hydraulic circuit to integrate both organ and cell level properties.