[Lipid metabolism-based analysis on the response mechanism of Ammopiptanthus mongolicus to low temperature stress]

Low temperature is a key environmental factor limiting plant growth. Under low-temperature stress, the biological membrane serves as the primary site of damage, with its lipid compositions undergoing significant alterations that are closely related to plant cold resistance. Ammopiptanthus mongolicus is an evergreen broad-leaved plant with exceptionally high stress tolerance, endemic to cold and arid desert areas. However, the regulatory mechanism of low-temperature induced membrane lipid metabolism remains unclear. In this study, an integrated approach combining physiological analyses, lipidomic profiling and gene functional validation was employed to elucidate the low-temperature response mechanism of Ammopiptanthusmongolicus. The results showed that low-temperature stress significantly increased the relative electrolyte conductivity, as well as the content of malondialdehyde, proline, soluble sugar, soluble protein and chlorophyll, along with the activity of superoxide dismutase in Ammopiptanthus mongolicus. Lipidomic analysis identified a total of 569 lipid molecules, among which glycerophospholipids constituted the predominant fraction. Low temperature induced lipid remodeling in Ammopiptanthus mongolicus, with 31 metabolites significantly upregulated and 26 metabolites significantly downregulated. The levels of phosphatidylserine, lysophospholipid, monogalactosyldiacylglycerol (MGDG) and glycosylceramide increased markedly, whereas the contents of phosphatidylcholine (PC) and triacylglycerol (TG) declined significantly. Furthermore, the proportions of polyunsaturated fatty acids in phosphatidic acid, PC, phosphatidylethanolamine (PE), diacylglycerol, and MGDG were significantly elevated. The real-time fluorescence quantitative reverse transcription polymerase chain reaction analysis revealed that low temperature markedly upregulated the expressions of fatty acid desaturase genes AmFAD2, AmFAD7, AmFAD8 and sphingolipid desaturase gene Am8SLD, while the expression of AmFAD3 and AmFAD6 were downregulated. Overexpression of AmFAD8 in Arabidopsisthaliana improved its freezing tolerance as well as membrane stability and antioxidant capacity under low-temperature stress. In summary, lipid molecules play a crucial role in the response of Ammopiptanthus mongolicus to low-temperature stress. This study fills the research gap regarding the cold adaptation mechanisms of extreme desert plants at the lipidomic level and provides critical theoretical support for the genetic improvement of cold-tolerant crops and forest trees.