Demystifying GMOs: New Research Shows Unexpected Changes in Plant DNA

Genetically modified organisms (GMOs)
are one of the most contentious topics in science today. But a
study from the Salk Institute,
published last month in
PLOS Genetics
, may help clear up some of the confusion. Using a
combination of techniques known as nanopore sequencing and optical
mapping, researchers believe they have a clearer picture of what
happens when genes are spliced into the genomes of plants and
animals.

In particular, the study showed that scientists can determine to
what extent surrounding areas of the host DNA have been affected by
gene splicing, a point that is often a source of concern for those
worried about the possible long-term impacts of
GMO consumption
.

How GMOs Are Created

To genetically modify a plant or animal, scientists first
sequence the entire genome of the organism to determine which
stretches of DNA have beneficial qualities. These would include
traits that help the organism survive drought, produce higher
nutrient densities, be less susceptible to insects or diseases, or
be able to withstand certain pesticides, among many others. The DNA
sequence containing desirable traits is then removed and implanted
into the genome of the host organisms, thereby transferring the
beneficial properties.

The most common method of doing this is by using the bacteria

Agrobacterium tumefaciens
. Several decades ago, it was
discovered that when this bacteria caused crown gall tumors on tree
trunks, some of the bacteria’s DNA was transferred into the DNA
of the tree; the bacteria’s transfer DNA (T-DNA), a circular
piece of DNA that can bind with other DNA sequences, was found to
be scattered throughout the tree. Since then, researchers have used
this bacteria’s T-DNA to help carry the desired genes into all
kinds of organisms.

Known Unknowns

However, the problem with this method is its lack of precision.
That is, when this process occurs, researchers are not sure exactly
what happens. Recent advancements in
DNA sequencing techniques
led some scientists to suspect that
the structure and chemistry of the host DNA might be changed more
than originally thought due to unknown interactions with the T-DNA,
as well as the amount and length of the T-DNA transferred into the
host.

Those designing and selling genetically modified products merely
test the new organism for the desired traits and, if they are
present, the process is considered a success.

Nanopore Sequencing and Optical Mapping

Originally created in the mid 1990s, nanopore
sequencing
is considered one of the most effective methods of
detecting genetic changes on a molecular level. It works by placing
two tiny electrodes near a nano-sized hole in a membrane filled
with an electrolyte. When a strand of DNA is sent through this
hole, the different bases that make up this molecule create unique
variations in the electric current, which can be detected and
analyzed. This allows researchers to know in great detail the
structure of the molecule that just passed through the hole.


Optical mapping
is a technique that creates a high-resolution
map of a genome by severing a strand of DNA at specific sites with
restriction
enzymes
, creating a unique fingerprint. That is, restriction
enzymes digest specific sequences of DNA, separating the strand
into various fragments, the distribution of which is inevitably
different from other strands.

While neither of these methods is entirely new, the Salk
Institute team combined them, creating a picture with an
unprecedented level of detail. They employed a new nanopore
long-read DNA sequencing technique, which made assembling the
picture of a complete genome much easier because it extends the
size of the data that can be collected, reducing the complexity of
assembling the pieces. They also created optical genome maps by
using the Bionano Genomics Irys system, which they demonstrated can
achieve levels of resolution on the scale of a single molecule.

The team found that one insertion attempt could result in as
many as seven unintended insertions or manipulations of the
host’s genome. Some of these were up to ten times larger than
intended, resulting in large segments of the host’s DNA being
damaged or relocated. Furthermore, the incoming DNA was sometimes
found to be out of place, cut in half, or out of sequence.

To GMO Or Not to GMO?

What these new results mean for the
GMO debate
is open to interpretation. Whatever side you might
be on, this research demonstrates there’s more happening on the
molecular scale than we originally thought.

Feeding the world’s future population is not only going to
involve
genetically modified foods
, it’s going to require them.
Current agricultural yields are not nearly high enough for the
projected
9.7 billion
people of 2050 to live on.

So what comes next to help determine whether GMOs are the way to
go, and how to make sure they’re safe? More research.

Image Credit:
science photo
/ Shutterstock.com

Source: *FS – All – Science News 2 Net
Demystifying GMOs: New Research Shows Unexpected Changes in Plant DNA