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

Abstract

38The mechanisms underlying rootzone-localised responses to salinity stress during early stage 39 of barley development remains fragmentary and elusive. Here, we performed a 40 comprehensive detection of the multi-root-omes (transcriptomes, metabolomes, lipidomes) of 41 a domesticated barley cultivar (Clipper) and a landrace (Sahara) with seedling root growth 42 maintained and restricted in response to salt stress, respectively. Novel generalized linear 43 models were designed to determine differentially expressed genes (DEG) or abundant 44 metabolites (DAM) specific to salt treatments, genotypes, or rootzones (meristematic Z1, 45 elongation Z2, maturation Z3). Based on pathway over-representation of the DEG and DAM, 46 phenylpropanoid biosynthesis is the most statistically over-represented biological pathways 47 among all salinity responses observed. Together with the histological evidence, an intense 48 salt-induced lignin impregnation was found only at the stelic cell wall of Clipper Z2, 49 comparing to a unique elevation of suberin deposition across Sahara Z2. This suggests two 50 differential salt-induced modulations of apoplastic flow between the genotypes. Based on 51 global correlation network construction of the DEG and DAM, callose deposition that 52 potentially adjusted the symplastic flow in roots was almost independent of salinity in 53 rootzones of Clipper, but was markedly decreased in that of Sahara. Through closer 54 examinations of molecular and hormonal clues, we further demonstrate that the salinity 55 response in rootzones of Clipper were mostly at recovery phase, comparing to Sahara with 56 rootzones retained at quiescence. Taken together, we propose that two distinctive salt 57 tolerance mechanisms could exist in Clipper (growth-sustaining) and Sahara (salt-shielding), 58 providing important clues for improving crop plasticity to cope with the deteriorating global 59 salinization of soil.60 61 4 109 to salinity stress differentially, suggesting the distinctive dynamics underpinning the 110 plasticity of different barley genotypes in response to salt stress. 111 6 RESULTS 112 113