Abstract:

Objective: The changes of metabolites and metabolic pathway in leaves of two Nitraria species under salt stress were studied in order to reveal the metabolic response mechanism of Nitraria to salt stress, which could provide the basic theory basis for effectively improving the sustainable biological improvement and adaptability of Nitraria to saline-alkali soil. Method: The seedlings of N.tangutorum And N.sibirica. were treated with 300 mmol·L^-1 NaCl with distilled water as the control. The effects of salt stress on metabolites and their metabolic pathways in leaves of two Nitraria species were analyzed by GC-TOF-MS metabonomics. Result: 1) There were 11 differentially expressed metabolites in the leaves of N.tangutorum under salt stress, 8 of which were significantly up-regulated, including 1 fatty acid, 5 organic acids, 1 alcohol and 1 base derivative, while there were 108 differentially expressed metabolites in the leaves of N.sibirica, 106 of which were significantly up-regulated, including 51 amino acids, 22 sugars, 11 fatty acids and 8 organic acid, 7 alcohols, 5 alkaloids and 2 vitamins. 2) Through KEGG annotation, the differentially expressed metabolites of N.tangutorum can be enriched into six metabolic pathways, and the key pathways that have the highest correlation with the difference of metabolites are sulfur metabolism, TCA cycle and dicarboxylic acid cycle through topological analysis, while the differentially expressed metabolites of N.sibirica can be enriched into 46 metabolic pathways, of which up to 13 are amino acid metabolism, and the key pathways arevaline, leucine and isoleucine biosynthesis, C5-Branched dibasic acid metabolism and pantothenate and CoA biosynthesis. Conclusion: The two Nitraria species have different metabolic response mechanisms to salt stress. N.tangutorum responds to salt stress through changes of 11 metabolites that are mainly composed of organic acids, and responds to salt stress by strengthening six metabolic pathways mainly composed of sulfur metabolism. N.sibirica responds to salt stress through changes of 108 metabolites, which mainly include amino acid, sugar and fatty acid, and also responds to salt stress by strengthening 46 metabolic pathways, mainly amino acid metabolism. The metabolites involved in the regulation of salt stress in N.sibirica have more species, more ways and more significant metabolic response to salt stress than those in N.tangutorum.

Key words: Nitraria tangutorum, Nitraria sibirica, differentially expressed metabolites, metabolic pathways, metabolic response