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, L p 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 L p r. HCR1 accumulates and is functional under combined O 2 limitation and potassium (K + ) sufficiency. HCR1 regulates L p 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 L p 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.