The endodermis is a key cell layer in plant roots that contributes to the controlled uptake of water and mineral nutrients into plants. In order to provide such functionality the endodermal cell wall has specific chemical modifications consisting of lignin bands (Casparian strips) that encircle each cell, and deposition of a waxy-like substance (suberin) between the wall and the plasma membrane. These two extracellular deposits provide control of diffusion enabling the endodermis to direct the movement of water and solutes into and out of the vascular system in roots. Loss of integrity of the Casparian strip-based apoplastic barrier is sensed by the leakage of a small peptide from the stele into the cortex. Here, we report that such sensing of barrier integrity leads to the rebalancing of water and mineral nutrient uptake, compensating for breakage of Casparian strips. This rebalancing involves both a reduction in root hydraulic conductivity driven by deactivation of aquaporins, and downstream limitation of ion leakage through deposition of suberin. These responses in the root are also coupled to a reduction in water demand in the shoot mediated by ABA-dependent stomatal closure.

Biochimie and Physiologie Moléculaire des Plantes Univ Montpellier CNRS INRA SupAgro Montpellier France

Department of Ecophysiology Institute of Cellular and Molecular Botany University of Bonn 53115 Bonn Germany

Department of Plant Molecular Biology University of Lausanne 1015 Lausanne Switzerland

Department of Plant Molecular Biology University of Lausanne 1015 Lausanne Switzerland Department of Botany and Plant Biology University of Geneva 30 quai Ernest Ansermet CH 1211 Geneva 4 Switzerland

Institute of Biological and Environmental Sciences University of Aberdeen Aberdeen AB24 3UU UK Department of Agronomy and Horticulture University of Nebraska Lincoln Lincoln NE 68588 0660 USA

Institute of Biological and Environmental Sciences University of Aberdeen Aberdeen AB24 3UU UK Division of Plant and Crop Sciences Future Food Beacon of Excellence and School of Biosciences University of Nottingham Nottingham LE12 5RD UK

Umeå Plant Science Centre Department of Forest Genetics and Plant Physiology Swedish University of Agricultural Sciences SE 901 83 Umeå Sweden

Umeå Plant Science Centre Department of Forest Genetics and Plant Physiology Swedish University of Agricultural Sciences SE 901 83 Umeå Sweden Laboratory of Growth Regulators Centre of the Region Haná for Biotechnological and Agricultural Research Faculty of Science of Palacký University and Institute of Experimental Botany of the Czech Academy of Sciences Olomouc Czech Republic

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