Comparative metabolomics unveils the role of metabolites and metabolic pathways in the adaptive mechanisms of shrubby halophytes

Salinity is a major abiotic stress that reduces agricultural production by impairing crop growth and development. Halophytes can complete their life cycle under high salinity conditions. In this study, primary metabolic pathways and metabolic marker were compared in three halophytes; Atriplex nummularia, A. griffithii and Salvadora persica. The principal component analysis (PCA) and partial least squares-discriminate analyses (PLS-DA) identified variations among halophytes. Furthermore, correlation analyses, metabolites network analyses and pathway impact/enrichment analyses revealed common metabolic pathways occurring in halophytes. Unequivocally, a total of 49 metabolites were identified from different metabolites classes such as amino acids, sugars, sugar alcohols (SAs), organic acids, and tricarboxylic acid cycles. The metabolic differences were noted for serine, norvaline, threonic acid, glucose, sucrose, mannitol, galactinol, and glycerol in S. persica as compared to Atriplex spp. The TCA cycle metabolites malic and citric acids were majorly found in A. nummularia, while succinic and 2-ketoglutaric acids were detected in A. nummularia and S. persica. Correlation-based networking and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway enrichment analysis revealed linkages of metabolites to major biological pathways like amino acid (AA) biosynthesis, carbohydrate metabolism, glyoxylate and dicarboxylate metabolism, arginine biosynthesis, galactose metabolism, butanoate metabolism, and the TCA cycle. The current work is the first to report on the metabolomic responses of shrubby halophytes in natural environmental conditions. The study’s findings, especially the coordination of multiple metabolic processes and pathways in shrubby halophytes, clarify how the plant adapts to harsh saline environments.