Metabolomics and network analysis reveal the potential metabolites and biological pathways involved in salinity tolerance of the halophyte Salvadora persica

Abstract

Salvadora persica L. (Miswak) is a facultative halophyte growing under high saline conditions. It has developed the adaptive characteristics to cope with high salinity because of its extreme habitat. The present study investigates the metabolomic responses of the halophyte S. persica imposed to long term salinity. This study will provide a systematic framework for understanding the underlying mechanisms and metabolic plasticity of S. persica for adaptation under high saline conditions. S. persica seedlings were imposed to various levels of salinity for 60 d. The metabolic profiling was carried out in leaf samples collected from control and NaCl-treated plants using GC–MS and HPLC analysis. The principal component analysis (PCA) and partial least squares-discriminate analysis (PLS-DA) were used for identifying the variations among control and treated groups. Furthermore, correlation based networking and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were employed for elucidation of metabolic pathways involved in salt tolerance of S. persica. In S. persica, a total of 56 metabolites belonging to different functional classes such as amino acids, TCA cycle intermediates, organic acids, sugars, sugar alcohols, phytohormones and fatty acids were changed by salinity. The fold change analysis showed that salinity induced major metabolic differences were noted for proline, methionine, phenylalanine, phosphonic acid, citric acid, galactaric acid, mandelic acid, caffeic acid, shikimic acid, gulonic acid, d-xylose, d-mannose, d-tagatose, d-mannitol, ABA, jasmonic acid, stearic acid and benzyl amine. Further assessment by correlation-based networking and KEGG pathway enrichment analysis demonstrated that the salinity-induced metabolites are associated with the major biological pathways related to amino acid biosynthesis, energy metabolism, carbohydrate metabolism, glycolysis, gluconeogenesis, pyruvate metabolism, TCA cycle, inositol phosphate metabolism, galactose metabolism and alkaloid biosynthesis. The present study is the first report on metabolomic responses to salinity in the halophyte S. persica. From our study, it was concluded that the coordination between various metabolic processes and pathways in S. persica enable the plant to adapt under extreme saline environment.