Changes in Membrane Fatty Acids in Cold-acclimated Turfgrass

Abstract

Three genotypes of seashore paspalum, `PI 299042', `Adalayd', and `PI 509018-1' considered to be cold-sensitive, intermediately cold-tolerant and cold-tolerant, respectively, were analyzed to investigate the biochemical basis of cold tolerance. The cultivars were acclimated to 8/4 °C day/night temperatures and rhizomes nodes and crowns were harvested at 7-day intervals over the 4-week experiment. Total lipid was extracted from these tissues, and the fatty acids present in the lipid fraction were identified by gas chromatography. Palmitic acid, stearic acid, linoleic acid and linolenic acid were the major fatty acids present. In cold acclimated tissues, the level of palmitic acid and stearic acid did not change significantly during the treatment period. There was a decrease in the level of linoleic acid by the second week of cold treatment. The amount of linolenic acid increased significantly during the second week of cold treatment corresponding to the decrease in linoleic acid. The change in the amount was significantly greater in `PI 509018-1' than in `Adalayd' or `PI 299042'. These results are similar to what was found for cultivars of bermudagrass that differ in their cold-tolerance phenotypes. Desaturases are enzymes involved in introducing the double bonds into the fatty acid chains. Research is underway to characterize and clone the genes encoding the Ω3, Ω6, and Ω9 desaturases, which may have an important role in affecting the cold tolerance by altering the degree of membrane lipid fatty acid saturation.