Metabolic profiling and gene expression analyses shed light on the cold adaptation mechanisms of Saposhnikovia divaricata (Turcz.) Schischk

The northeastern region of China experiences a distinctly cold climate influenced by the Siberian High during the winter months, thus resulting in severe cold weather conditions. Snow cover is prevalent and can persist for several months. This prolonged exposure to low temperatures necessitates specific adaptations in terms of agriculture and plant life, particularly for perennial herbs. Saposhnikovia divaricate (Turcz.) Schischk (SD) is a widely distributed perennial herb in the northeastern and northern provinces of China. However, there is limited documentation on the molecular mechanism through which this plant adapts to cold stress. Therefore, we elucidated the SD response to cold stress by transcriptome and metabolome analysis. Cold stress induced chlorosis and wilting in plants, thus leading to added function of antioxidant enzymes and higher levels of malondialdehyde, proline, soluble sugars. Notably, the differentially expressed genes (DEGs) were primarily related with sugar metabolism, ROS sweep, flavonoid and terpenoid biosynthesis, plant hormone signalling pathways, lipid metabolism, and transcription factors. Additionally, the differentially expressed metabolites (DEMs) mainly included lipids, flavonoids, terpenoid compounds, sugar-related metabolites, alkaloids and other metabolites. Furthermore, integrated analysis revealed coexpression patterns between carbohydrate metabolism-related genes and genes reference flavonoid and terpenoid biosynthesis, along with their corresponding metabolites. Finally, the qPCR results revealed notable over-expression levels of stress-related genes, including those participated in plant hormone signalling pathways (PP2C and AUX), flavonoid biosynthesis (CH3), antioxidant enzymes (AOX and CAT), and sugar-related metabolite metabolism (TPS, SPS, and SS). In conclusion, our findings suggest that cold stress strongly affects plant hormone signalling pathways, ROS scavenging mechanisms, unsaturated fatty acid synthesis and flavonoid and terpenoid biosynthesis in SD. These discoveries provide valuable insights into the impact of cold climates on herbaceous plants.