The desC gene for the acyl-lipid Delta9-desaturase from the thermophilic cyanobacterium Synechococcus vulcanus was introduced into Nicotiana tabacum under control of the 35S promoter. Expression of the desaturase was confirmed by Western blotting. Lipid analysis revealed that lipid content and the extent of fatty acid unsaturation significantly increased in leaves of transgenic plants. Chilling tolerance of those plants also increased, as estimated by the electrolyte leakage from the tissues damaged by cold treatments. Seeds of plants that expressed the desC gene imbibed at low temperatures demonstrated higher chilling tolerance than those of the control plants. The results demonstrate that the cyanobacterial thermophilic acyl-lipid desaturase was efficiently expressed in tobacco at ambient temperatures, and its expression resulted in the enhanced chilling tolerance of the transgenic plants.

Tobacco plants with the introduced desC gene for acyl-lipid ∆ 9-desaturase from the thermophilic cyanobacterium Synechococcus vulcanus were cultivated on agar-solidified Murashige and Skoog nutrient medium supplemented with ferulic acid and antibiotics at 22 ° C and a 16-h photoperiod. Control plants were transformed with an empty pGA482 vector. The analysis of fatty acids (FAs) showed that, in transgenic plants, the level of 16:0 and 18:0 FAs decreased substantially, whereas the levels of di-and trienoic FAs increased. Transformed plants were more cold-tolerant. The tolerance to chilling was evaluated from electrolyte leakage from tissues damaged by cold treatments and from the accumulation of a product of lipid peroxidation, malondialdehyde. It was concluded that acyl-lipid ∆ 9-desaturase was actively expressed in transgenic tobacco plants and converted stearic acid into oleic acid, thus producing a substrate for further synthesis of di-and trienoic FAs. An increased proportion of polyunsaturated FAs in membrane lipids resulted in improved tobacco plant tolerance to chilling.

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