A Receptor-Like Kinase Mediates Ammonium Homeostasis and Is Important for the Polar Growth of Root Hairs in Arabidopsis

The study identified CAP1, a receptor-like kinase in Arabidopsis, as crucial for maintaining ammonium (NH4+) homeostasis and essential for the polar growth of root hairs. CAP1 regulated NH4+ transport to the vacuole, maintaining cytoplasmic calcium (Ca2+) gradients necessary for root hair development. Mutants lacking CAP1 (cap1) showed disrupted Ca2+ gradients and impaired root hair growth due to excess cytoplasmic NH4+. Complementation with wild-type CAP1 restored normal growth, confirming its role. The findings underscored CAP1's importance in NH4+ detoxification and root hair development through calcium signaling and nutrient uptake.