understanding of the biochemical processes underlying fatty
acid biosynthesis, according to Maheshwari and Kavolchuk.
Because the “seed oil content of plants is controlled by
multiple steps in the oil biosynthetic pathway,” they write,
it is unrealistic to expect the insertion of a single gene will
result in a dramatic increase in oil yield. To boost yields,
not only do the right genes need to be present, the proteins they encode need to be expressed at the proper levels, in the proper tissues, and at the proper time. But there
are a few simple strategies involving single gene modifications that hold promise for improving oil content, such as
down-regulating genes to reduce levels of unwanted fatty
acids, or overexpressing other genes to increase the desired
ones. (See Table 2).
Once a GE oil seed is created, researchers must also
insure that (1) the oils stored in the seeds don’t interfere
with the germination process, resulting in unviable seeds,
(2) the transgenes are expressed at optimal levels, and (3)
that the oils produced aren’t toxic to the plant itself and
don’t interfere with other cellular processes (Biocat. Agric.
Biotech., 3:31-37, 2014).
UP-AnD-coMIng tecHnIqUes For
The two commonly used approaches to creating GE crops—
Agrobacterium tumefaciens and microprojectile bombardment—share one major downside: Both techniques cause
the gene-of-interest to insert into the host’s DNA at random, which can result in the disruption and/or truncation
of native genes.
To address this shortcoming, researchers have been
working to develop other transformation methods that
would scientists to determine the exact spot in which a
gene will be inserted.
Here’s a sampling of some of the up-and-coming techniques for genome editing:
• clustered regularly interspaced short palindromic
repeats (CRISPRs) are DNA molecules, inspired by
naturally occurring CRISPRs found in bacteria and
archaea, that can be designed to insert into an
organism at any desired location (Nat. Rev. Genetics, 11:181-190, 2010).
• transcription activator-like effector nucleases
(Nat. Biotech, 29:135-136, 2011) and zinc-finger
nucleases (Gen. Soc. Am., 188:773-782, 2011)
belong to the family of enzymes known as artificial restriction enzymes. They contain two primary components: a DNA binding domain, which
recognizes a specific DNA sequence, and a DNA
cleavage domain, which cuts the DNA to enable
the gene-of-interest to insert into the genome at
a pre-determined location.
tHe FUtUre oF genetIc engIneerIng
The biggest push so far for commercialized GE oilseed crops
thus far has been for herbicide- and pest-resistant crops,
which directly address farmers’ needs. But some experts
expect the industry will soon be making a shift toward crops
that directly meet consumers’ needs and demands, such as
with the creation of oils that have more healthful fatty acid
profiles. “That story’s just occurring now,” Knowlton said.
Another important research avenue for GE oilseed crops
involves engineering “metabolic pathways for production
of exotic fatty acids into more traditional oilseed crops,”
wrote Dyer and Mullen (Seed Sci. Res., 15:255-267, 2005).
A plant with the ability to create oils normally produced in
fish, such as the widely popular omega-3 fatty acids DHA
and EPA, would find enormous value among both industry
and consumers. As a step in this direction, researchers at
Monsanto have announced plans to commercialize a GE
soybean oil rich in stearidonic acid, which the body can convert into EPA, an omega-3 fatty acid that may help maintain
heart health (Lipids, 43:805-811, 2008).
Other efforts have been made to increase the amount
of oil content present in a plant’s leaves, which could lead to
kinney, A.j., J. Food Lipids
Buhr, t., et al., Plant J. (30:155-163, 2002)
α-linolenic acid eckert, H., Planta (224:1050-1057, 2006)
sato, s., et al. Crop Sci. (44:646-652, 2004)
eckert, H., Planta (224:1050-1057, 2006)
Harris, W.s., Lipids (43:805-811, 2008)
epoxy fatty acid
li, r., et al., Plant Biotechnol. J.
rao, s.s. and D. Hildebrand, Lipids
lardizabal et al., Plant Physiol.
(148: 89-96, 2008)
li, r., et al., Plant Biotechnol. J.
table 2: For nearly two decades, researchers have been using the
tools of genetically engineering to create crops with higher levels of
desired fatty acids. Here’s a sampling of GE soybean crops. Adapted
from: Biocat. Agric. Biotech., 3:31-37, 2014.