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

Abstract

The perception and relay of cell-wall signals are critical for plants to regulate growth and stress responses, but the underlying mechanisms are poorly understood. We found that the cell-wall leucine-rich repeat extensins (LRX) 3/4/5 are critical for plant salt tolerance in <i>Arabidopsis</i> The LRXs physically associate with the RAPID ALKALINIZATION FACTOR (RALF) peptides RALF22/23, which in turn interact with the plasma membrane-localized receptor-like protein kinase FERONIA (FER). The <i>lrx345</i> triple mutant as well as <i>fer</i> mutant plants display retarded growth and salt hypersensitivity, which are mimicked by overexpression of <i>RALF22</i>/<i>23</i> Salt stress promotes S1P protease-dependent release of mature RALF22 peptides. Treatment of roots with mature RALF22/23 peptides or salt stress causes the internalization of FER. Our results suggest that the LRXs, RALFs, and FER function as a module to transduce cell-wall signals to regulate plant growth and salt stress tolerance.