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 Ca2+ 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.