PLASMA-MEMBRANE LIPIDS ASSOCIATED WITH GENETIC-VARIABILITY IN FREEZING TOLERANCE AND COLD-ACCLIMATION OF SOLANUM SPECIES

Simultaneous comparisons were made between a freezing-tolerant, cold-a cclimating (CA) wild potato species (Solanum commersonii) and a freezi ng-sensitive, nonacclimating (NA) cultivated species (Solanum tuberosu m). Comparative studies allowed differentiation of plasma membrane lip id changes associated with increased freezing tolerance following CA f rom lipid changes that can result from metabolic adjustment to reduced temperature during CA. Following CA treatment lipid changes found in both the NA and CA species included a decrease in palmitic acid, an in crease in unsaturated to saturated fatty acid ratio, an increase in fr ee sterols, an increase in sitosterol, and a slight decrease in cerebr osides. Lipid changes detected only in the acclimating species include d an increase in phosphatidylethanolamine, a decrease in sterol to pho spholipid ratio, an increase in linoleic acid, a decrease in linolenic acid, and an increase in acylated steryl glycoside to steryl glycosid e ratio. These changes were either absent or opposite in the NA specie s, suggesting an association of these lipid changes with CA. Furthermo re, the lipid changes associated with increased freezing tolerance dur ing CA were distinct from lipid differences between the two species in the NA state.