Two winter rapeseed cultivars, “NS” (cold tolerant) and “NF” (cold sensitive), were used to reveal the morphological, physiological, and proteomic characteristics in leaves of plants after treatment at -4°C for 12 h(T1) and 24 h(T2), and at room temperature(T0), to understand the molecular mechanisms of cold tolerance. Antioxidant activity and osmotic adjustment ability were higher, and plasma membrane injury was less obvious, in NS than in NF under cold stress. We detected different abundant proteins (DAPs) related to cold tolerance in winter rapeseed through data-independent acquisition (DIA). Compared with NF, A total of 1,235 and 1,543 DAPs were identified in the NSs under T1 and T2, respectively. Compared with NF, 911 proteins were more abundant in NS only after cold treatment. Some of these proteins were related to ROS scavenging through four metabolic pathways: lysine degradation; phenylalanine, tyrosine, and tryptophan; flavonoid biosynthesis; and ubiquinone and other terpenoid-quinone biosynthesis. Analysis of these proteins in the four candidate pathways revealed that they were rapidly accumulated to quickly enhance ROS scavenging and improve the cold tolerance of NS. These proteins were noticeably more abundant during the early stage of cold stress, which was critical for avoiding ROS damage.

A study on physiological, biochemical and differential protein expression response mechanisms was conducted by with two breeds of winter rapeseed (Brassica rapa L.), DR-7 (drought resistant) and Tianyou 5 (drought sensitive), under drought stress. The results showed that leaves in winter rapeseed wilted, the edge of the leaf gradually withered, the relative water content in the leaf decreased and the contents of osmotic regulatory substances and malondialdehyde in the leaf rose with increasing drought intensity due to cell membrane damage under dry conditions. Twenty-three differentially expressed proteins (DEPs) were selected by two-dimensional gel electrophoresis with liquid chromatography mass spectrometry (LC-MS) analysis under drought stress; These proteins were related to lipid metabolism, protein/amino acid metabolism, metabolic pathways, linoleic acid metabolism, oxidative phosphorylation processes, response to stress, energy metabolism and photosynthesis. Among the DEPs, three were involved in ATP metabolism and three in fatty acid metabolism. Furthermore, with increasing drought intensity, the activities of Na⁺/K⁺-ATPase and Ca²⁺/Mg²⁺-ATPase in leaves gradually decreased; The content of saturated fatty acids (SFAs) in membrane system significantly increased, which together with the enzyme activity is crucial to cell metabolism; And polyunsaturated fatty acids (PUFAs) slightly increased. According to the results, the damage in membrane system due to SFAs was alleviated by the increase of PUFA content, increasing the ability of winter rapeseed to resist drought. Overall, the increase of osmotic regulatory substances contents and the decrease in osmotic potential in winter rapeseed due to drought stress improve water absorption and regulate the expression of related proteins. thus improving resistance to drought. Increasing of PUFA content were advantageous to the function of the membrane-bound enzyme ATPase.

Brassica napus L. is a vital plant oil resource worldwide. The fatty acid biosynthesis and oil accumulation in its seeds are controlled by several genetic and environmental factors, including daytime and nighttime temperatures. We analyzed changes in oleic and erucic acid content in two double haploid (DH) lines, DH0729, a weakly temperature-sensitive line, and DH0815, a strongly temperature-sensitive line, derived from B. napus plants grown at different altitudes (1600, 1800, 2000, 2200, and 2400 m a.s.l., 28.85° N, 112.35° E) and nighttime temperatures (20/18, 20/16, 20/13 and 20/10 °C, daytime/nighttime temperature). Based on medium- and long-chain fatty acid metabolites, the total oleic acid content 35 and 43 days after flowering was significantly lower in low nighttime temperature (LNT, 20/13 °C) plants than in high nighttime temperature (HNT, 20/18 °C) plants (HNT: 58–62%; LNT: 49–54%; an average decrease of 9%), and the total erucic acid content was significantly lower in HNT than in LNT plants (HNT: 1–2%; LNT: 8–13%; an average increase of 10%). An RNA-seq analysis showed that the expression levels of SAD (LOC106366808), ECR (LOC106396280), KCS (LOC106419344), KAR (LOC106367337), HB1(LOC106430193), and DOF5 (LOC111211868) in STSL seeds increased under LNT conditions. In STSL seeds, a base mutation in the cis-acting element involved in low-temperature responsiveness (LTR), the HB1 and KCS promoter caused loss of sensitivity to low temperatures, whereas that of the KCS promoter caused increased sensitivity to low temperatures.