Leucine-rich repeat extensin proteins regulate plant salt tolerance in <i>Arabidopsis</i>

Significance Plants have evolved cell-wall integrity signaling pathways to maintain cell-wall homeostasis in response to stress conditions, but the components involved in the perception and transduction of cell-wall signals are largely unknown. Here we found that the Arabidopsis cell-wall–localized leucine-rich repeat extensins (LRX) 3/4/5 interact with RAPID ALKALINIZATION FACTOR (RALF) peptides RALF22/23. Mature RALF22/23 peptides interact with the plasma membrane-localized FERONIA (FER) and induce FER internalization. The lrx345 and fer mutants and RALF22 / 23 overexpressing transgenic plants display similar phenotypes such as retarded growth and increased sensitivity to salt stress. Our work thus reveals that the LRX3/4/5 proteins function with RALF22/23 and FER to define a signaling pathway that is critical for regulating plant growth and salt tolerance.