Remodeling of the Leaf Lipidome During Cold Acclimation, De-Acclimation and Re-Acclimation Influences the Frost Tolerance of Festuca Arundinacea.

Seasonal temperature increases in autumn and winter can significantly disrupt frost tolerance in plants. This inducible trait is acquired during cold acclimation, reduced or lost during de-acclimation, and potentially restored during re-acclimation. The functionality of cellular membranes, closely associated with lipid composition, plays a crucial adaptive role in enabling plants to withstand low-temperature stress. However, studies focusing on effects of de-acclimation and re-acclimation on frost tolerance, particularly in forage grasses, remain limited. Here, we assessed frost tolerance in high (HFT) and low frost tolerant (LFT) genotypes of Festuca arundinacea following cold acclimation, de-acclimation, and re-acclimation, based on the assessment of their cellular membranes integrity as reflected by the parameter describing the temperature causing 50% level of electrolyte leakage from cells. Analyses of membrane integrity and lipid composition during cold acclimation revealed that the HFT genotype maintained greater membrane stability through extensive remodeling of glycerolipids, including increased lipid unsaturation, particularly in phosphatidylethanolamine (PE), preserved a balanced monogalactosyldiacylglycerol/digalactosyldiacylglycerol (MGDG/DGDG) ratio, and enhanced triacylglycerol (TAG) accumulation, compared to the LFT genotype. De-acclimation reversed rearrangements in structural lipids and reduced frost tolerance, whereas re-acclimation induced strong genotype-dependent responses, especially in phosphoglycerolipids profiles. Analysis of mRNA accumulation profiles indicated key enzymes potentially involved in lipid remodeling. Major transcriptional changes were observed in phytyl ester synthase 1 (PES1), digalactosyldiacylglycerol synthase (DGD1), and lipoxygenase (LOX) family transcripts, indicating their importance during cold acclimation, de-acclimation, and re-acclimation. Collectively, these findings demonstrate, for the first time, that genotype-dependent lipid remodeling underlies the capacity of F. arundinacea to maintain and recover frost tolerance. We further suggest that stress-induced TAG accumulation may function as a protective metabolic buffer, sequestering excess free fatty acids, limiting lipid oxidation, and supporting membrane stability under low-temperature stress.