Résumé
Soil water uptake by roots is central for plant growth and survival. Flooding, as many other environmental constraints such as drought, nutrient deprivation or oxidative stress exerts deep effects on root functions by altering root water permeability (root hydraulic conductivity; Lpr). These effects, which are mediated mainly through the regulation of aquaporins, are fundamental for adaptation of wild plant species to diverse natural habitats and a major target for crop improvement. However, the signaling mechanisms which link soil properties to root hydraulics and aquaporin functions remain largely unknown. We have been investigating the genetic bases of root hydraulics in the model plant, Arabidopsis thaliana. Using quantitative genetics approaches, including linkage mapping and genome-wide association mapping, we have identified several genes controlling Lpr. The signaling pathway for regulation of Lpr by a RAF-like MAP3 kinase named Hydraulic Conductivity of Root 1 (HCR1) will be discussed in details (Shahzad et al (2016) Cell 167: 87-98.e14). This protein kinase delineates a combinatorial signaling pathway integrating two soil signals, K+ and O2 availability, to regulate root hydraulics and hypoxia responsive genes, through the control of RAP2.12, a key transcriptional regulator of the core anaerobic response. In addition, several other candidate genes identified during this study offer interesting perspectives for understanding as yet unknown mechanisms involved in the regulation of root hydraulics.