Upton, New York
March 5, 2007
Technique could yield materials to replace petrochemicals and
more nutritious edible oils
Using genetic manipulation to
modify the activity of a plant enzyme, researchers at the
U.S. Department of Energy's
Brookhaven National Laboratory have converted an unsaturated
oil in the seeds of a temperate plant to the more saturated kind
usually found in tropical plants. The research will be published
online by the Proceedings of the National Academy of Sciences
(PNAS) the week of March 5, 2007.
While conversion of an
unsaturated oil to an oil with increased saturated fatty acid
levels may not sound like a boon to those conscious about
consuming unsaturated fats, "the development of new plant seed
oils has several potential biotechnological applications," said
Brookhaven biochemist John Shanklin, lead author on the paper.
For one thing, the new
tropical-like oil has properties more like margarine than do
temperate oils, but without the trans fatty acids commonly found
in margarine products. Furthermore, engineered oils could be
used to produce feedstocks for industrial processes in place of
those currently obtained from petrochemicals. Shanklin also
suggests that the genetic manipulation could work in the reverse
to allow scientists to engineer more heart-healthy food oils.
"Scientists have known for a
long time that the ratio of saturated to unsaturated fatty acids
plays a key role in plants' ability to adapt to different
climates, but to change this ratio specifically in seed oils
without changing the climate is an interesting challenge,"
remarked Shanklin. "Our group sought to gain a better
understanding of the enzymes and metabolic pathways that produce
these oils to find ways to manipulate the accumulation of fats
using genetic techniques."
The researchers focused on an
enzyme known as KASII that normally elongates fatty acid chains
by adding two carbon atoms. The longer 18-carbon chains are more
likely to be acted on by enzymes that desaturate the fat. So the
scientists hypothesized that if they could prevent the chain
lengthening by reducing the levels of KASII, they could decrease
the likelihood of desaturation and increase the level of
saturated fats in the plant seeds.
Their hypothesis was supported
by the fact that scientists had previously identified a plant
with a mutated KASII that showed reduced enzyme activity, and
these plants were able to accumulate more saturated fats than
was normal. So the Brookhaven team set out to reduce KASII
activity with the use of RNA-interference (RNAi) to see if they
could further increase the level of saturation in plant seed
oils.
The Brookhaven scientists
performed their experiments on Arabidopsis, a plant commonly
used in research. Like other plants from temperate climates
(e.g., canola, soybean, and sunflower), Arabidopsis contains
predominantly 18-carbon unsaturated fatty acids in its seed oil.
Tropical plants, in contrast (e.g. palm), contain higher
proportions (approximately 50 percent) of 16-carbon saturated
fatty acids.
The results were surprising.
The genetic manipulations that reduced KASII activity resulted
in a seven-fold increase in 16-carbon unsaturated fatty acids —
up to an unprecedented 53 percent — in the temperate Arabidopsis
plant seed oils.
"These results demonstrate that
manipulation of a single enzyme's activity is sufficient to
convert the seed oil composition of Arabidopsis from that of a
typical temperate pant to that of a tropical palm-like oil,"
Shanklin said. "It is fascinating — and potentially very useful
— to know that we can change the oil composition so drastically
by simple specific changes in seed oil metabolism, and that this
process can occur independently from the adaptation to either
tropical or temperate climates."
For example, such a technique
could lead to the engineering of temperate crop plants to
produce saturated oils as renewable feedstocks for industrial
processes. Such renewable resources could help reduce dependence
on petroleum.
Conversely, methods to increase
the activity of KASII, and therefore the production of 18-carbon
desaturated plant oils, may provide a useful strategy to limit
the accumulation of saturated fatty acids in edible oils,
leading to more healthful nutrition.
This work was funded by the
Office of Basic Energy Sciences within the U.S. Department of
Energy's Office of Science, and by Dow and Dow Agrosciences.
Co-authors included Brookhaven biologist Tam Nguyen, Mark
Pidkowich of the University of British Columbia, and Ingo
Heilmann and Till Ischebeck of the Georg-August University of
Göttingen.
The PNAS paper should be
available later today at:
http://www.pnas.org/cgi/doi/10.1073/pnas.0611141104
One of ten national
laboratories overseen and primarily funded by the Office of
Science of the U.S. Department of Energy (DOE), Brookhaven
National Laboratory conducts research in the physical,
biomedical, and environmental sciences, as well as in energy
technologies and national security. Brookhaven Lab also builds
and operates major scientific facilities available to
university, industry and government researchers. Brookhaven is
operated and managed for DOE's Office of Science by Brookhaven
Science Associates, a limited-liability company founded by the
Research Foundation of State University of New York on behalf of
Stony Brook University, the largest academic user of Laboratory
facilities, and Battelle, a nonprofit, applied science and
technology organization. |
