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Improved production of polyunsaturated fats in oilseed crops will benefit
human health and the environment, September, 2004 .

In research reported this month in The Plant Cell, scientists succeeded in
producing genetically modified linseed plants that accumulate significant
levels of very long chain poly-unsaturated fatty acids (PUFA) in seed. This
is the first report of the successful engineering of very long chain PUFA
into an oilseed crop, and is an excellent example of how genetic engineering
of agronomically important species can provide real benefits to human health
and nutrition and the environment.

In research reported this month in The Plant Cell, Ernst Heinz at the
University of Hamburg (Germany) and colleagues succeeded in producing
genetically modified linseed plants that accumulate significant levels of
very long chain poly-unsaturated fatty acids (PUFA) in seed. The work is the
result of an international collaboration between scientists at several
research institutions in Germany (University of Hamburg, BASF Plant Science
GmbH and Forschungszentrum Borstel), Rothamsted Research Station in the
U.K., and Kansas State University in the U.S. This research is an excellent
example of how genetic engineering of agronomically important species can
provide real benefits to human health and nutrition and the environment. As
demand rises for edible oils that are low in saturated fats and high in
poly-unsaturated fats, in particular very long chain omega 3- and omega
6-poly-unsaturated fats, the production of these oils in plants may reduce
environmentally and economically unsustainable pressures on both wild and
farmed fisheries.

Fatty acids are long straight chains of carbon atoms, ranging in length from
about 12 to 22 carbons (C12 to C22). They have one water-soluble end and one
oil-soluble methyl end, and are studded with hydrogen atoms along the length
of the carbon chain. They are essential components of the membranes of all
living organisms. Fatty acid chains that are linked by single bonds between
carbon atoms are said to be "saturated" by hydrogen atoms, whereas the
introduction of double bonds between carbon atoms leads to correspondingly
fewer bonds to hydrogen atoms along the chain, and such fatty acids are said
to be "unsaturated". A "mono-unsaturated" fatty acid contains a single
double bond within the carbon chain, whereas "poly-unsaturated" fatty acids
contain two or more double bonds.

PUFA are increasingly recognized as important components of a healthy human
diet. Increased consumption, in particular of the very long chain PUFA such
as those found in fish oils, has been linked to a decreased risk of heart
disease, and also to a variety of other health benefits, including
protection against inflammatory diseases such as arthritis, irritable bowel
syndrome and some cancers, and the promotion of healthy brain and eye
development in infants. Scientists have been working on engineering the
production of the very long chain PUFA in plants, because increased
consumption of fish and fish oils is associated with other nutritional and
environmental problems. First, it is recommended that consumption of many
types of fish be limited due to widespread contamination with pollutants,
such as heavy metals and dioxins. Second, world wide fish stocks are being
rapidly depleted, and fish farming is associated with its own set of
environmental issues. Therefore, engineering the production of very long
chain PUFAs into oilseed crops could confer significant advantages in terms
of both human nutrition and the environment.

Oilseed crops, such as canola, safflower, and linseed, typically accumulate
a high proportion of C18 PUFA such as linoleic acid and alpha-linoleic acid
in their seed. These are called "essential" fatty acids for humans, because
they are not synthesized in the human body and must be obtained from dietary
sources. Once consumed, they may be metabolized into very long chain (C20
and C22) PUFA in the human body. However, this process is slow and
inefficient compared to the direct consumption of C20 and C22 PUFA that may
be obtained from fish oils. Oilseed crop species contain all of the proteins
and enzymes necessary for the biosynthesis of the range of fatty acids
present in seed oil, but they lack the few additional enzymes (certain fatty
acyl desaturases and elongases) necessary for the biosynthesis of very long
chain PUFA.

Dr. Heinz and his colleagues produced linseed (Linum usitatissimum) and
tobacco (Nicotiana tabacum) plants that synthesize very long chain PUFA in
their seed by introducing genes for fatty acyl desaturases and elongases in
genetic transformation experiments. First, protein sequences for fatty acyl
desaturases and elongases were analyzed from a variety of organisms that
produce very long-chain PUFA, including a fungus (Mortierella alpina), alga
(Phaeodactylum tricornutum), moss (Physcomitrella patens), nematode
(Caenorhabditis elegans), and another plant (Borago officinalis). DNA coding
sequences for these genes were then introduced into linseed and tobacco
plants, and expression of the proteins directed into the seed with the use
of seed-specific gene promoter sequences. The best results were obtained
with the use of the plant and algal gene sequences. These transgenic plants
accumulated significant levels of very long chain PUFA in their seed.
Analysis of fatty acid profiles of these plants also allowed the researchers
to identify constraints on the accumulation of the most desirable PUFA,
pointing the way to future experiments aimed at making improvements in the
levels of accumulation and specific profiles of very long chain PUFAs in
genetically modified oilseed crops. In addition to the possibility of
providing healthier, more nutritious oils for human consumption, this work
will lead to the production of high quality animal feed that could improve
the PUFA content of animal products such as meat, eggs, and dairy foods.

This research is the result of an international collaboration between
scientists at the University of Hamburg, BASF Plant Science and
Forschungszentrum Borstel in Germany, Rothamsted Research station in the
U.K. and Kansas State University in the U.S. Funding was provided by grants
from the German BMBF-Projekt NAPUS 2000 and BASF Plant Science GmbH
(Ludwigshafen, Germany), with additional support from the Kansas National
Science Foundation Experimental Program to Stimulate Competitive Research
(EPSCoR).

The full research paper cited in this report is available at
[www.aspb.org]

The Plant Cell (http://www.plantcell.org) is published by the American
Society of Plant Biologists.

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