Quantitative and qualitative analysis of lipids in genetically modified potato tubers with varying rates of 14-3-3 protein synthesis.

In six transgenic lines of potatoes with the varying rates of 14-3-3 protein synthesis as well as in control cultivar Desiree the content and composition of the lipids extracted from the mature tubers from three years field trials (1998-2000) were analyzed. The transgenic lines J2 and J1 are both overexpressing gene encoding 14-3-3 protein. The J2 exhibited an overexpression of the protein 14-3-3 derived from pumpkin (Cucurbita pepo) cDNA and in J1 the 14-3-3 overexpression resulted from modifying of ADP-ribosylation factor synthesis. In the remaining lines, synthesis of the protein 14-3-3 was modified by the antisense technology. In tubers from 1998, the content of total lipids was within the range of 0.45-0.88% of tuber dry matter. The highest amount of fat was in tubers of line J2 (69% more than in the control). The content of lipids in tubers from subsequent years ranged from 0.36 to 0.63% of dry matter. Consistently the highest amount of fat was in tubers of line J2, however, the increase was very slight (8.6% more than in the control). The fractionation of lipids into polar and nonpolar fractions showed that all transgenic lines from field trials 1998 and 2000 contained more nonpolar lipids than the control (up to 270% in line J2). The percentage of nonpolar fractions in fats of tubers from all transgenes harvested in 1999 were similar, but they were higher than in tubers from the previous years, and they amounted to 44.4-49.1%. Chromatographic separation of methyl esters of fatty acids demonstrated that cis-alpha-linoleic acid was the main fatty acid present in potato tubers. This acid composed the biggest part of all lipids in G2 line. In the nonpolar fraction of lipids, palmitic acid followed by cis-alpha-linoleic acid showed the highest amounts.