Differential gene expression patterns and physiological responses improve adaptation to high salinity concentration in pepper accessions

Abstract

High salinity decreases the productivity of crops worldwide. Pepper is particularly sensitive to high salt concentrations. Herein, we subjected three tolerant pepper accessions (C12, B14 and A25) to high sodium chloride concentration (70 mM NaCl). The aerial and root biomass, leaf and root osmotic potential (Ψ_π ), Na⁺ , Cl^- , K⁺ and proline concentrations and the relative expression of the putative genes CaSOS1, CaHKT1, three CaNHXs and CaP5CS were measured. Different salinity tolerance strategies depending on the pepper accession were identified. In C12, tolerance was attributed to the accumulation of Na⁺ in vacuoles and endosomes by the activation of vacuolar CaNHXs genes and the reduction in Ψ_π ; additionally, the activation of CaHKT1 and CaSOS1 in leaves and roots moved and accumulated Na⁺ ions in the xylem and xylem parenchyma cells (XPC) as well as expulsed it out of the root cells. A25 accession, on the contrary, was specialized in compartmentalizing Na⁺ ions in root and leaf vacuoles and root XPC by the up-regulation of CaNHXs and CaHKT1, respectively, avoiding a toxic accumulation in leaves. Finally, B14 accession moved and accumulated Na⁺ in xylem and XPC, reducing its concentration in roots by the activation of CaSOS1 and CaHKT1. This study shade light on different tolerance mechanisms of pepper plants to overcome salt stress.