Integrated transcriptomics and metabolomics analysis to characterize alkali stress responses in canola (Brassica napus L.)

Soil salinization is a major constraint limiting agricultural development and affecting crop growth and productivity, especially in arid and semi-arid regions. Understanding the molecular mechanism of the adaptability of canola to salt stress is very important to improve the salt tolerance of canola and promote its cultivation in saline alkali soil. To identify the metabolomic and transcriptomic mechanisms of canola under alkaline salt stress, we collected roots of control (no salt treatment) and 72 h Na2CO3-stressed canola seedlings (hydroponics) for metabolic profiling of metabolites, supplemented with RNA-Seq analysis and real-time quantitative PCR validation. Metabolomic analysis showed that the metabolites of amino acids and fatty acids were higher accumulated under alkaline salt stress, including L-proline, L-glutamate, L-histidine, L-phenylalanine, L-citrulline, L-tyrosine, L-saccharopine, L-tryptophan, linoleic acid, dihomo gamma linolenic acid, alpha linolenic acid, Eric acid, oleic acid and neuronic acid, while the metabolism of carbohydrate (sucrase, alpha, alpha trehalose), polyol (ribitol), UDP-D-galactose, D-mannose, D-fructose and D-glucose 6-phosphate decreased. Transcriptomic and metabolomic pathway analysis indicated that carbohydrate metabolism may not play an important role in the resistance of canola to alkaline salt stress. Organic acid metabolism (fatty acid accumulation) and amino acid metabolism are important metabolic pathways in the root of canola under alkaline salt stress. These results suggest that the genes and metabolites involved in fatty acid metabolism and amino acids metabolism in roots of canola may regulate salt tolerance of canola seedlings under alkaline salt stress, which improves our understanding of the molecular mechanisms of salt tolerance in canola.