Integrative Multi-Omics Analyses of Barley Rootzones Under Salinity Stress Reveal Two Distinctive Salt Tolerance Mechanisms

Abstract Mechanisms underlying rootzone-localised responses to salinity during early stage of barley development remains elusive. Here, we detected the multi-root-omes (transcriptomes, metabolomes, lipidomes) of a domesticated barley cultivar (Clipper) and a landrace (Sahara) which maintain and restrict seedling root growth under salt stress, respectively. Novel generalized linear models were designed to determine differentially expressed genes (DEG) and abundant metabolites (DAM) specific to salt treatments, genotypes, or rootzones (meristematic Z1, elongation Z2, maturation Z3). Based on pathway over-representation of the DEG and DAM, phenylpropanoid biosynthesis is the most statistically enriched biological pathways among all salinity responses observed. Together with histological evidence, an intense salt-induced lignin impregnation was found only at stelic cell wall of Clipper Z2, comparing to a unique elevation of suberin deposition across Sahara Z2. This suggests two differential salt-induced modulations of apoplastic flow between the genotypes. Based on global correlation network of the DEG and DAM, callose deposition that potentially adjusted symplastic flow in roots was almost independent of salinity in rootzones of Clipper, and was markedly decreased in Sahara. Taken together, we propose two distinctive salt tolerance mechanisms in Clipper (growth-sustaining) and Sahara (salt-shielding), providing important clues for improving crop plasticity to cope with deteriorating global soil salinization.