Abstract

1 - Plant Stress Resilience, Institute of Environmental Biology, Utrecht University, Utrecht, the Netherlands; 2 - Laboratory of Plant Physiology, Wageningen University, Wageningen, the Netherlands; 3 - Biochemistry, Wageningen University, Wageningen University, the Netherlands; 4 - Molecular Plant Physiology, Department of Biology, Philipps-Universität Marburg, 35043 Marburg, Germany;

Abstract text: Salt is detrimental to plant growth. Recent studies have highlighted the role of cell wall changes in regulating the plant's response to salt stress. To identify the responsible proteins for this change, we conducted proteomics analysis of apoplastic proteins from Arabidopsis seedlings treated with and without NaCl. Our study revealed different groups of proteins with varying abundances in the apoplast. Among them, we focused on the characterization of 3 subtilisin-like proteases (SBTs) 1.1, 1.6, and 5.3. Previously, SBTs have been described to control small signaling peptide maturation. Building on the known role of SBT1.1 in the proteolytic cleavage of PRO-PHYTOSULFOKINE 4 (PROPSK4), we analyzed the phenotype of pskr1pskr2, PSK receptor mutants, upon salt stress. This mutant displayed impaired growth, suppressed expression of salt-responsive genes, and increased lignin deposition upon salt application. Surprisingly, exogenous application of PSK-α peptide inhibits MPK6 phosphorylation, reduces salt-stress-related gene expression, decreases lignin accumulation, and improves growth under salt stress. Additionally, adding the PSK-α peptide reduces NaCl-induced methylation of carbohydrates and the cell wall-associated monosaccharide, suggesting that alteration of cell wall composition might alleviate the NaCl stress response.