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 Arabidopsis 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 lrx345 triple mutant as well as fer mutant plants display retarded growth and salt hypersensitivity, which are mimicked by overexpression of RALF22/23 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.
Highlights
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
It has been shown that the Arabidopsis lrx3 lrx4 double and lrx3 lrx4 lrx5 triple mutants are defective in cell-wall composition and display growth retardation [23] (Fig. 1 A and B)
The retarded growth and salthypersensitive phenotypes of the lrx34 mutant were complemented by expressing a wild type (WT) LRX3-coding sequence (CDS) (SI Appendix, Fig. S1 B and C), supporting that the lrx mutations are the cause of the observed mutant phenotypes
Summary
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. 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. Treatment of plants with RALF23 peptides decreases ligand-induced association of the FLS2/EFRBAK1 complex via the inhibition of FER protein [15] These versatile functions of FER are likely attributed to its role in the sensing and relay of cell-wall integrity signals. It was reported that FER is required for the recovery of root growth after plants are exposed to high salinity stress, and FER may sense salt-induced cell-wall changes through direct binding to pectin [6]. Several groups reported that LRX8–LRX11 proteins are important for cell-wall integrity regulation during pollen tube growth [24,25,26,27]. The LRX8– LRX11 proteins function together with RALF4/19 peptides to regulate pollen tube growth [27]
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