A Potassium-Dependent Oxygen Sensing Pathway Regulates Plant Root Hydraulics

Aerobic organisms survive low oxygen (O-2) through activation of diverse molecular, metabolic, and physiological responses. In most plants, root water permeability (in other words, hydraulic conductivity, Lp(r)) is downregulated under O-2 deficiency. Here, we used a quantitative genetics approach in Arabidopsis to clone Hydraulic Conductivity of Root 1 (HCR1), a Raf-like MAPKKK that negatively controls Lp(r). HCR1 accumulates and is functional under combined O-2 limitation and potassium (K+) sufficiency. HCR1 regulates Lp(r) and hypoxia responsive genes, through the control of RAP2.12, a key transcriptional regulator of the core anaerobic response. A substantial variation of HCR1 in regulating Lp(r) is observed at the Arabidopsis species level. Thus, by combinatorially integrating two soil signals, K+ and O-2 availability, HCR1 modulates the resilience of plants to multiple flooding scenarios.