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Haloxylon salicornicum is a xero-halophyte growing in saline and arid regions of the world. Metabolite profiling was carried out in shoot of both control and salinity treated (400 mM NaCl) samples by GC-QTOF–MS and HPLC-DAD analysis to decipher the salinity tolerance mechanism in this xero-halophyte. The present study investigates the alteration in metabolite profile of H. salicornicum that support the salinity tolerance of the plant. The metabolomic analysis of H. salicornicum shoot identified 56 metabolites, of which 47 metabolites were significantly changed in response to salinity. These metabolites were mainly included in the category of amino acids, organic acids, amines, sugar alcohols, sugars, fatty acids, alkaloids, and phytohormones. In response to salinity, most of the amino acids were down-regulated except alanine, phenylalanine, lysine, and tyramine, which were up-regulated in H. salicornicum. In contrast to amino acids, most sugars and organic acids were up-regulated in response to salinity. Correlation and pathway enrichment analysis identified important biological pathways playing significant roles in conferring salt tolerance of H. salicornicum. These biological pathways include amino sugar and nucleotide sugar metabolism, citrate cycle (TCA cycle), starch and sucrose metabolism, phenylalanine metabolism, cysteine, methionine, glycine, serine, and threonine metabolism, etc. The data presented here suggest that the modulations of various metabolic pathways facilitate H. salicornicum to survive and grow optimally even under high salinity condition. This study offers comprehensive information on metabolic adaptations and overall salt tolerance mechanisms in H. salicornicum. The information gained through this study will provide guidance to plant breeders and molecular biologists to develop salinity tolerant crop varieties. Image 1 • Metabolomic responses triggered by salinity was studied in xero-halophyte H. salicornicum. • Higher TCA cycle activity suggest uninterrupted energy supply for optimum growth. • Elevated level of sugars suggests its role as osmo-regulators, instead of amino acids. • Increased β-oxidation provides sufficient energy to maintain optimum growth under salinity. [ABSTRACT FROM AUTHOR]

Water deficit severely limits productivity of plants, and pose a major threat to modern agriculture system. Therefore, understanding drought adaptive mechanisms in drought-tolerant plants is imperative to formulate strategies for development of desiccation tolerance in crop plants. In present investigation, metabolic profiling employing GC-QTOF-MS/MS and HPLC-DAD was carried out to evaluate metabolic adjustments under drought stress in the xero-halophyte Salvadora persica. The metabolite profiling identified a total of 68 metabolites in S. persica leaf, including organic acids, amino acids, sugars, sugar alcohols, hormones, and polyphenols. The results showed that higher cellular osmolality under drought stress was accompanied by accumulations of several osmoprotectants like sugars and polyols (sucrose, glucose, mannose, galactose, erythrose, sorbose, glycerol, and myoinositol), organic acids (galactaric acid, tartaric acid, malic acid, oxalic acid, and citric acid), and amino acids (alanine, phenylalanine, tyrosine). Upregulation of ABA and JA support to achieve early drought tolerance in S. persica. Moreover, accumulation of coumarin, gallic acid, and chlorogenic acid provide antioxidative defense to S. persica. KEGG pathway enrichment analysis showed that altered metabolites were associated with starch and sucrose metabolism, galactose metabolism, inositol phosphate metabolism, and phenylalanine metabolism. While during recovery, metabolites associated with lysine biosynthesis and alanine, aspartate and glutamate metabolism were significantly altered. The results of the present study imply that coordinated regulations between various metabolites, metabolic processes, and pathways empower the xerohalophyte S. persica to adapt under drought environment. The knowledge from this study will enable the development of drought tolerance in crops using genetic engineering and breeding approaches. Image 1 • Metabolite profiling identified 68 metabolites in the xero-halophytic plant Salvadora persica. • Functional classes of drought-inducible metabolites are amino acids, sugars, sugar alcohols, organic acids, and polyphenols. • Sugars provide osmotic homeostasis, antioxidant defense and stress signals under drought stress. • Upregularions of ABA, JA, gallic acid, chlorogenic acid, and coumarin aids to achive drought tolerence. • Metabolome was not completely returned to control levels suggesting stress imprint for future stress. [ABSTRACT FROM AUTHOR]