| Wild type and transgenic tomato suspension cultures were established to examine changes in fatty acid composition profiles when cells express a Δ-9 desaturase gene (OLE1). The medium formulation was optimized to obtain a final composition that made use of Gamborg's B5 medium with 3% sucrose, 5 μg/L kinetin and 10 μg/L 2,4-D. The established suspension cultures were used for fatty acid analysis studies. The transgenic cultures showed a 61% decrease in palmitic acid (16:0) content from 700 μg/g fcw to 270 μg/g fcw, and a 47 fold increase in palmitoleic acid (16:1) content from 12 μg/g fcw to 560 μg/g fcw compared to wild type cultures. Transformation had a positive effect on the growth rate of cell cultures. In particular, transgenic cell cultures were observed to grow to a final concentration of 23.5 g dcw/L in 12 days whereas the wild type cells reached a maximum level of 19 g dcw/L during the same time period.; Both cell cultures were subjected to exogenous addition of 4mg/g fcw of palmitic (16:0) and stearic (18:0) acid into the growth medium. In wild tomato suspension cultures this led to an increase in the intracellular fatty acid content. Of all the corresponding unsaturated derivatives the most dramatic result was seen in the 85 fold increase in 16:3 content following addition of 16:0. In contrast transgenic cell cultures showed decreases in the 16 carbon unsaturated fatty acid content, when spiked with palmitic acid. The level of stearic acid and its unsaturated derivatives, however, was increased. This suggests that the exogenously supplied fatty acids are sequestered intracellularly in such a way that they are not immediately available to the desaturase enzyme and undergo elongation. Nevertheless, perturbations throughout the fatty acid profile of transgenic cell lines can be seen following addition of saturated precursors. |
