To overcome the problem of poor accumulation, we performed a series of systematic metabolic engineering experiments to optimize the accumulation of omega-7 fatty acids in transgenic plants, Shanklin said. For these proof-of-principle experiments, the scientists worked with Arabidopsis, a common laboratory plant.
Enzymes that make the unusual fatty acids are variants of enzymes called desaturases, which remove specific hydrogen atoms from fatty acid chains to form carbon-carbon double bonds, thus desaturating the fatty acid. First the researchers identified naturally occurring variant desaturases with desired specificities, but they worked poorly when introduced into Arabidopsis. They next engineered a laboratory-derived variant of a natural plant enzyme that worked faster and with greater specificity than the natural enzymes, which increased the accumulation of the desired fatty acid from less than 2 percent to around 14 percent.
Though an improvement, that level was still insufficient for industrial-scale production. The scientists then assessed a number of additional modifications to the plants metabolic pathways. For example, they down-regulated genes that compete for the introduced enzymes fatty acid substrate. They also introduced desaturases capable of intercepting substrate that had escaped the first desaturase enzyme as it progressed through the oil-accumulation pathway. In many of these experiments they observed more of the desired product accumulating. Having tested various traits individually, the scientists then comb
|Contact: Karen McNulty Walsh|
DOE/Brookhaven National Laboratory