Transcriptomic and metabolomics-based analysis of key biological pathways reveals the role of lipid metabolism in response to salt stress in the root system of Brassica napus

Soil salinity is a major constraint affecting crop growth and productivity, and limiting sustainable agricultural development in arid zones. Understanding the molecular mechanisms underlying the adaptation of canola to salt stress is important to improve salt tolerance and promote its cultivation in saline soils. To elucidate the metabolic and transcriptional regulatory mechanisms in canola under salt stress, the seedling roots of the control (no salt treatment) and roots of canola seedlings subjected to 72 h of 200 mM NaCl stress (hydroponics) were collected for metabolomic analysis, supplemented with RNA-Seq analysis and quantitative real-time PCR (qRT-PCR) validation. Metabolomic analysis showed that compared with the control, the metabolites of lipids accumulated more under NaCl stress, including unsaturated fatty acids (linoleic acid, dihomo-gamma-linolenic acid, oleic acid, nervonic acid, alpha-linolenic acid), glycerophospholipids (1-palmitoyl- sn -glycero-3-phosphocholine, 1-oleoyl- sn -glycero-3-phosphocholine, 1-stearoyl-2-hydroxy- sn -glycero-3-phosphocholine) lecithin (phosphorylcholine), sphingolipids ( N -palmitoylsphingosine) and steroids and steroid derivatives (25-hydroxyvitamin D3); while the metabolism of most amino acids (such as l -valine, l -threonine, l -isoleucine, l -glutamate, l -phenylalanine) and carbohydrates (such as d -fructose, cellobiose, sucrose, d -mannose) were lower. Both transcriptomic and metabolomic pathway analysis indicated that lipid metabolism was an important metabolic pathway in canola roots under NaCl stress. In summary, canola seedling roots could respond to NaCl stress through lipid metabolism genes and metabolites, which improved our knowledge in molecular mechanisms encoding NaCl tolerance in canola.