July 27, 2017 — Which is more disruptive to a plant: genetic engineering or conventional breeding?
It often surprises people to learn that GE commonly causes less disruption to plants than conventional techniques of breeding. But equally profound is the realization that the latest GE techniques, coupled with a rapidly expanding ability to analyze massive amounts of genetic material, allow us to make super-modest changes in crop plant genes that will enable farmers to produce more food with fewer adverse environmental impacts. Such super-modest changes are possible with CRISPR-based genome editing, a powerful set of new genetic tools that is leading a revolution in biology.
My interest in GE crops stems from my desire to provide more effective and sustainable plant disease control for farmers worldwide. Diseases often destroy 10 to 15 percent of potential crop production, resulting in global losses of billions of dollars annually. The risk of disease-related losses provides an incentive to farmers to use disease-control products such as pesticides. One of my strongest areas of expertise is in the use of pesticides for disease control. Pesticides certainly can be useful in farming systems worldwide, but they have significant downsides from a sustainability perspective. Used improperly, they can contaminate foods. They can pose a risk to farm workers. And they must be manufactured, shipped and applied — all processes with a measurable environmental footprint. Therefore, I am always seeking to reduce pesticide use by offering farmers more sustainable approaches to disease management.
What follows are examples of how minimal GE changes can be applied to make farming more environmentally friendly by protecting crops from disease. They represent just a small sampling of the broad landscape of opportunities for enhancing food security and agricultural sustainability that innovations in molecular biology offer today.
Genetically altering crops the way these examples demonstrate creates no cause for concern for plants or people. Mutations occur naturally every time a plant makes a seed; in fact, they are the very foundation of evolution. All of the food we eat has all kinds of mutations, and eating plants with mutations does not cause mutations in us.
Knocking Out Susceptibility
A striking example of how a tiny genetic change can make a big difference to plant health is the strategy of “knocking out” a plant gene that microorganisms can benefit from. Invading microorganisms sometimes hijack certain plant molecules to help themselves infect the plant. A gene that produces such a plant molecule is known as a susceptibility gene.
We can use CRISPR-based genome editing to create a “targeted mutation” in a susceptibility gene. A change of as little as a single nucleotide in the plant’s genetic material — the smallest genetic change possible — can confer disease resistance in a way that is absolutely indistinguishable from natural mutations that can happen spontaneously. Yet if the target gene and mutation site are carefully selected, a one-nucleotide mutation may be enough to achieve an important outcome.
There is a substantial body of research showing proof-of-concept that a knockout of a susceptibility gene can increase resistance in plants to a very wide variety of disease-causing microorganisms. An example that caught my attention pertained to powdery mildew of wheat, because fungicides (pesticides that control fungi) are commonly used against this disease. While this particular genetic knockout is not yet commercialized, I personally would rather eat wheat products from varieties that control disease through genetics than from crops treated with fungicides.
The Power of Viral Snippets
Plant viruses are often difficult to control in susceptible crop varieties. Conventional breeding can help make plants resistant to viruses, but sometimes it is not successful.
Early approaches to engineering virus resistance in plants involved inserting a gene from the virus into the plant’s genetic material. For example, plant-infecting viruses are surrounded by a protective layer of protein, called the “coat protein.” The gene for the coat protein of a virus called papaya ring spot virus was inserted into papaya. Through a process called RNAi, this empowers the plant to inactivate the virus when it invades. GE papaya has been a spectacular success, in large part saving the Hawaiian papaya industry.
Aerial view of a field trial showing virus-resistant papaya growing well while the surrounding susceptible papaya is severely damaged by the virus. Reproduced with permission from Gonsalves, D., et al. 2004. Transgenic virus-resistant papaya: From hope to reality in controlling papaya ringspot virus in Hawaii. APSnet Features. Online. DOI: 10.1094/APSnetFeature-2004-0704
Through time, researchers discovered that even just a very small fragment from one viral gene can stimulate RNAi-based resistance if precisely placed within a specific location in the plant’s DNA. Even better, they found we can “stack” resistance genes engineered with extremely modest changes in order to create a plant highly resistant to multiple viruses. This is important because, in the field, crops are often exposed to infection by several viruses.
Does eating this tiny bit of a viral gene sequence concern me? Absolutely not, for many reasons, including:
- These snippets and the plant defenses they trigger were part of our diet long before genetic engineering was invented.
- The inserted genetic material comes from viruses that infect plants, not mammals.
- We are inserting extremely limited, incomplete fragments of the virus’s genome.
- These viruses — and so these molecules — are much, much more abundant in naturally infected crops (which we eat all the time) than in GE crops.
Tweaking Sentry Molecules
Microorganisms can often overcome plants’ biochemical defenses by producing molecules called effectors that interfere with those defenses. Plants respond by evolving proteins to recognize and disable these effector molecules. These recognition proteins are called “R” proteins (“R” standing for “resistance”). Their job is to recognize the invading effector molecule and trigger additional defenses. A third interesting approach, then, to help plants resist an invading microorganism is to engineer an R protein so that it recognizes effector molecules other than the one it evolved to detect. We can then use CRISPR to supply a plant with the very small amount of DNA needed to empower it to make this protein.
This approach, like susceptibility knockouts, is quite feasible, based on published research. Commercial implementation will require some willing private- or public-sector entity to do the development work and to face the very substantial and costly challenges of the regulatory process.
Engineered for Sustainability
The three examples here show that extremely modest engineered changes in plant genetics can result in very important benefits. All three examples involve engineered changes that trigger the natural defenses of the plant. No novel defense mechanisms were introduced in these research projects, a fact that may appeal to some consumers. The wise use of the advanced GE methods illustrated here, as well as others described elsewhere, has the potential to increase the sustainability of our food production systems, particularly given the well-established safety of GE crops and their products for consumption. 
Editor’s note: The views expressed here are those of the author and not necessarily of Ensia.
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For example. A carpenter may understand the principles of building a roulette table. This 'expertise' in building a roulette table is not 'expertise' in the calculating the chances of 'winning' or 'losing' at the table. Another example, a worker may understand perfectly how to make a deck of playing cards without knowing anything about how to calculate the probablilities of being dealt a royal flush.
This author shows no particular understanding of risk.
His use of cards to persuade is inapt because it falsely presents the risks as 'knowable' and controllable. The demonstration should show new types of cards say a "27 of giraffes" or a "12 of donkey" which could create and unknown "hand" 2 aces and one 27 of giraffes creates a 'bezumpt'. And
you don't know what a 'bezumpt' can do. Humans are playing with a fundamental force of the universe like a child may play with a nuclear weapon. It may not go off 27 out of 28 times or 999,999 times out of 1,000,000 but it will go off and then the game of life has ended.
Here is a link to an article that explains the differences in knowledge better than I can.
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwjB68XL9tbVAhXIqlQKHeQ5A00QFggoMAA&url=https%3A%2F%2Farxiv.org%2Fpdf%2F1410.5787&usg=AFQjCNFyKIywV8FZnTNIUaNkRfWjumpFxg
http://www.fooledbyrandomness.com/PrecautionaryPrinciple.html
We and many people that we know would almost immediately reach for food labeled Proudly GMO for the reasons of less pesticide use, healthier product, often higher nutrition conferred, etc. But how do we begin to make traction against this irrational and pervasive "frankenfood" soundbite?
First, let me say that scientists like me, who see value in the wise use of genetic engineering (GE) of crops, are equally concerned about food safety and other issues of risk, so we appreciate the concerns of critics. And, having taken a careful, in-depth look at the rather massive scientific literature on GE, most experts have concluded that there is no evidence of novel, intrinsic risks from GE. This scientific judgement started appearing in peer-reviewed papers as early as the 1980s, so this seems to be a well-established scientific finding.
Risk is often understood to be the product of hazard times exposure. Addressing the “exposure” factor in this relationship is easy: If a citizen wishes to eliminate their dietary exposure to GE crops, s/he can do so by eating non-GMO foods, and I support that choice—not for scientific reasons but for social reasons—to support the food choices of all citizens. As far as the “hazard” factor, it is worth repeating that, after close to four decades of research, there is no validated evidence of novel, intrinsic risk to food safety resulting from GE, nor is there evidence of a unique and intrinsic biophysical or chemical change to DNA as a result of GE. This is why thinking of GE as analogous to word processing is useful (see Part 1 in http://www2.ca.uky.edu/anr/Biotech/biotech.htm). Of course, a hazard can be introduced through GE, just as a hazard can be introduced through conventional breeding. However, many scientific organizations have carefully evaluated the hazards of GE crops and have reach essentially the same conclusion--that there is no novel, intrinsic risk from GE of crops. Our National Academy of Sciences, as well as other prestigious scientific organizations worldwide, state that risk should be evaluated based on the particular features of new plant variety, not on how genetic changes were made.
I encourage readers to follow the links I included in the article above, as well as the links in the following articles of mine:
• Consumption of Genetically Engineered (=GMO) Crops: Examples of Quotes from Position Papers of Scientific Organizations https://kentuckypestnews.wordpress.com/2015/03/31/consumption-of-genetically-engineered-gmo-crops-examples-of-quotes-from-position-papers-of-scientific-organizations/.
• NAS Report on GE Crops has Overall Support of Leading Independent Scientists https://vincelliblog.wordpress.com/2016/12/30/nas-report-on-ge-crops-has-overall-support-of-leading-independent-scientists/
• Genetic Engineering and Plant Disruption https://vincelliblog.wordpress.com/2016/10/09/genetic-engineering-and-plant-disruption/
After reading these, a reader may still wonder about those few papers that suggest concern. Just like the topic of human-influenced climate change, we find that there are a few papers that end up in peer-reviewed journals that do not fit with prevailing scientific thinking. On the one hand, this is a good thing: good scientists should and do take all dissenting papers seriously, as scientists must always be open to revising our thinking in the face of new data. On the other hand, we commonly find that dissenting papers do not hold up well to expert scientific scrutiny, and actually were never suitable for publication. After all, while peer review provides a good check against publication of papers of questionable quality, it is an imperfect process performed by imperfect humans, so sometimes undeserving papers “squeak through.” With respect to GE crops, see the examples in this recent, open-access review paper: http://onlinelibrary.wiley.com/doi/10.1111/pbi.12798/abstract
One of the things I find to be most important is that no one has proposed a scientifically validated mechanism for how GE would introduce a novel, intrinsic risk to food safety. I respect that some people will continue wishing to avoid eating GE crops, and I support that choice. Everyone should feel safe in their food choices. However, for the rest of us, at some point in a risk assessment, good scientific practice calls for a reasonable mechanism of hazard to be hypothesized and, of course, carefully and rigorously tested. Since no such validated mechanism exists in the scientific literature, most scientists accept the conclusions of publishing experts that there is no novel, intrinsic risk to food safety from GE crops, and that each new plant variety must be evaluated for its own particular risks and benefits.
Yes, there are concerns with respect to GE, but the possibility of uncharacterized, speculative risks to food safety is no longer a convincing argument to most experts. This is not wishful thinking—this is simply what peer-reviewed scientific evidence shows. If it were not so, I would be the first to say so, but my commitment, and my obligation, is to report credible science findings to the public. This is simply what the science shows.