Integrative Multi-Omics Analysis of Barley Genotypes Shows Differential Salt-Induced Osmotic Barriers and Response Phases Among Rootzones

The mechanisms underlying rootzone-localised responses to salinity during early stage of barley development remains fragmentary and elusive. We performed a multi-root-ome analysis of two barley cultivars with differential root growth in response to salinity. Novel generalized linear models were designed to determine differentially expressed genes or abundant metabolites specific to salt treatments, genotypes, or rootzones. Based on pathway over-representation of the DEG and DAM, phenylpropanoid biosynthesis is the most statistically over-represented biological pathway observed. Together with histological evidence, an intense salt-induced lignin impregnation was found only at the stelic cell wall of Clipper Z2, comparing to a unique elevation of suberin deposition across Sahara Z2 suggesting two differential salt-induced modulations of apoplastic flow between the genotypes. Based on global correlation network construction of the DEG and DAM, callose deposition that potentially adjusted the symplastic flow in roots was almost independent of salinity in Clipper. Through closer examinations of molecular and hormonal clues, we demonstrate that the salinity response in rootzones of Clipper were mostly at recovery phase, comparing to Sahara with rootzones retained at quiescence. We propose that two distinctive salt tolerance mechanisms exist, providing important clues for improving crop plasticity to cope with the deteriorating global soil salinization.