A potassium-sensing niche in Arabidopsis roots orchestrates signaling and adaptation responses to maintain nutrient homeostasis.

Organismal homeostasis of the essential ion K requires sensing of its availability, efficient uptake, and defined distribution. Understanding plant K nutrition is essential to advance sustainable agriculture, but the mechanisms underlying K sensing and the orchestration of downstream responses have remained largely elusive. Here, we report where plants sense K deprivation and how this translates into spatially defined ROS signals to govern specific downstream responses. We define the organ-scale K pattern of roots and identify a postmeristematic K-sensing niche (KSN) where rapid K decline and Ca signals coincide. Moreover, we outline a bifurcating low-K-signaling axis of CIF peptide-activated SGN3-LKS4/SGN1 receptor complexes that convey low-K-triggered phosphorylation of the NADPH oxidases RBOHC, RBOHD, and RBOHF. The resulting ROS signals simultaneously convey HAK5 K uptake-transporter induction and accelerated Casparian strip maturation. Collectively, these mechanisms synchronize developmental differentiation and transcriptome reprogramming for maintaining K homeostasis and optimizing nutrient foraging by roots.