Temperature- dependent regulation of fatty acid desaturases genes in potato cells

Under fluctuating temperatures, physical state and fluidity of cellular and subcellular membranes is maintained by regulating the Ievel of unsaturation of membrane lipids. The phenomenon is widespread and well-known also in the plant kingdom. We ha ve cloned two full-Iength cONA clones, encoding respec- tively a delta-9 and delta-l2 desaturases, key-enzymes of the pathway of lipid unsaturation, of Solanum commersonii, a cold tolerant wild potato species. Ex- pression of both genes was down-regulated by a graduaI up-ward shift (2°C/h from 28 up to 37°C) of the growth temperatures of a potato cell suspension culture, but not when temperature was increased abruptly (heat shock). Upon cold-acclimation (4°C/15 d), transcription of the delta-12 desaturase was in- creased in the cold-tolerant potato species, but not in S. tuberosum, the cultivated species that is known to be unable lo cold-acclimate. This finding is consistent with the increase in linoleic acid (18:2) of plasma membrane reported for S. commersonii upon cold-acc1imation. Taken together, our data demonstrate that regulation of the expression of this c1ass of gene is temperature-dependent and may account at least partially for the variation in the level of membrane lipid unsaturation induced by changes in growth temperatures.