OMG GMO! Part 2: Are GMOs bad?

My first post in this series laid out some of the basic facts about genetically modified organisms, including what they are and how they are made. I encourage you to read that if you haven’t already.

When we talk about GMOs, there is one question that inevitably comes up.

Are GMOs bad?

This is a tricky subject. There are a lot of articles out there that make the claim that there’s no such thing as a good GMO and that all of them are bad in some way. Others would have you believe that they are all completely harmless. I'm going to talk about three different GMO crops that have made headlines over the years and I’ll leave it to you to come to your own conclusion.

Golden rice

Carrots are one of the best sources of beta-carotene, but not the only one. Sweet potatoes, kale, squash, apricots, and red peppers are just a few of the tasty alternatives. Image courtesy of Wikimedia commons.

Carrots are one of the best sources of beta-carotene, but not the only one. Sweet potatoes, kale, squash, apricots, and red peppers are just a few of the tasty alternatives. Image courtesy of Wikimedia commons.

Aid workers in some of the poorer parts of India and Southeast Asia were noticing a problem. People were not getting enough vitamin A in their diets, leading to a number of health problems, particularly in children. Millions of people all over the world are afflicted with vitamin A deficiency, which can lead to blindness and can even be fatal (WHO 2015). When people have access to a balanced diet, they get all of the vitamin A that they need from their food in the form of provitamin A or beta-carotene (which is what gives foods like carrots, tomatoes, and peppers their color), but in many parts of the world, people don’t have access to such foods. Of course the ideal solution is to help people get access to a better diet, but that’s easier said than done. There is a mountain of logistical problems that prevent people from growing nutrient-rich food. Another possible solution is to provide vitamin supplements, but this is not a long-term fix as such programs require special training, medical staff, distribution infrastructure, and can cost millions of dollars to maintain (MOST 2004).

Golden Rice (left) grain compared to white rice grain (right). Image courtesy of International Rice Research Institute (IRRI) via Wikimedia commons.

Golden Rice (left) grain compared to white rice grain (right). Image courtesy of International Rice Research Institute (IRRI) via Wikimedia commons.

A team of scientists started working on a solution in the 1990’s. They inserted several genes into the genome of Oryza sativa (Asian rice) that code for the enzymes that produce beta-carotene. The researchers tried many different sources for beta-carotene genes and found that those from corn (Zea mays) produced the most provitamin A in rice (Paine et al. 2005). Rice was a good candidate for modification because it is the staple food for millions of people in Southeast Asia, India, and the Indo-Pacific islands, areas where vitamin A deficiency is common. That way there doesn’t have to by any training, or changes to diet or infrastructure; all that they have to do is grow a different kind of rice. With an improved strain developed in 2004, Golden Rice was set to treat vitamin A deficiency for people around the world (Golden Rice Project 2015).

Widespread release of Golden Rice has been delayed for a number of social and political reasons, but testing is underway in the Philippines (International Rice Research Institute 2015).

Roundup ready crops

Molecular structure of glyphosate.

Molecular structure of glyphosate.

One of the most widespread modifications of food crops in the United States is known as the Roundup ready trait. Roundup is the trade name of glyphosate, a broad spectrum herbicide that has seen widespread use. Glyphosate works by interfering with an enzyme that is involved with the synthesis of the amino acids Tyrosine, Tryptophan, and Phenylalanine. Without those amino acids, the plants can’t make proteins and therefore can’t grow properly. That makes glyphosate very effective at killing weeds, but also very effective at killing most other plants (a weed is still a plant after all), as well as some microbes that rely on the same enzyme to make their own amino acids (Glyphosate facts 2013).

A group of biotech researchers found naturally occurring bacteria (Agrobacterium sp.) that wasn’t affected by glyphosate. The bacteria have a different form of the enzyme targeted by glyphosate. The enzyme still makes the exact same product, it just takes a different path to get there. That small change allows Agrobacterium sp. to evade the effects of glyphosate. The scientists isolated the gene responsible for the different enzyme, created a plasmid with it (along with some other necessary DNA sequences), and inserted it into the genome of soy plants using a gene gun (Funke et al. 2006). The same modification has since been applied to corn, alfalfa, and several other crops. Now a field growing one of these transgenic crops can be sprayed with glyphosate, killing the weeds, but leaving the desired crops intact.

Bt crops

Tobacco plants growing in a field. Photo by and (c)2006 Derek Ramsey via Wikimedia Commons.

Tobacco plants growing in a field. Photo by and (c)2006 Derek Ramsey via Wikimedia Commons.

One of the next things to be targeted by genetic engineers was the pests (particularly insects) that plague farmers. They wanted to create a crop that produces its own pesticides. This is not an entirely new idea; Nature is way ahead of us on that. The leaves of tobacco plants (Nicotina sp.), for instance, naturally contain nicotine to deter herbivorous insects. In fact many commercial pesticides are derived from nicotine (just in case you needed another reason not to smoke). What makes Bt crops different is that scientists have figured out how to get plants to produce a pesticide that comes from a different species, the bacterium Bacillus thuringiensis (Bt for short). It produces a crystalline proteinaceous insecticidal δ-endotoxin (shortened to crystalline proteins or simply CRY proteins) which has been used since the 1920s by spraying crops with either the bacterial spores (dormant bacterial cells), or with the extracted toxin (Bravo et al. 2007). One of the advantages to this pesticide is that it is specific to only certain types of insects. CRY is activated by alkaline digestive systems - which are only found in flies, moths, wasps, and beetles – then further modified by enzymes in the insects’ digestive tract before it becomes harmful. Our digestive systems (and those of all vertebrates) are acidic, so the toxin remains dormant.

Bt-toxin-crystals like these have been extraxted from bacteria and used as pesticides for nearly 100 years. Now they can be produced directly by plants. Photo by Jim Buckman via Wikimedia Commons.

Bt-toxin-crystals like these have been extraxted from bacteria and used as pesticides for nearly 100 years. Now they can be produced directly by plants. Photo by Jim Buckman via Wikimedia Commons.

As you might have guessed, the gene that makes CRY was isolated and inserted into a plant’s genome. Now there are crops that are deadly to most of the insects that plague farmers, but are considered by the EPA to be safe for humans (EPA 2011).

Is that all?

These are only three of the most talked about GMOs, but by no means all of them. Scientists all over the world are working to create new modifications for all sorts of different purposes. Politicians are deciding how to regulate genetic modification, and people everywhere are trying to make sense of all of the information. Hopefully this post has shed a little bit of light on the subject for you.

I have a confession to make at this point. I'm not actually going to tell you if GMOs are good or bad. The modifications themselves are neutral, so the question is really about how they are used. Some are intended to help feed people, some are created to help farmers get better crop yields, and some are made for financial gain. It's even possible that a GMO crop can do all three of those things. You'll have to look at the facts and make your own judgments. Don't hesitate to ask your friendly neighborhood scientist either. Check back later as I delve into some of the concerns and controversies surrounding GMOs.

 

References