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Humans love to play with their food—in fact, we’ve been doing it for thousands of years. In this episode of Crash Course Botany, we'll explore how we’ve learned to manipulate plant genetics, from breeding tastier fruits and veggies to directly editing plant genes that help crops survive climate change. And if you’ve ever wondered what GMOs are or if they’re safe, we’ve got you covered.

Playing With Our Food 0:00
Plant Genetics & Breeding 1:04
What Are GMOs? 4:15
How GMOs Are Made 5:01
Ancient GMOs 6:33
Are GMOs Safe? 8:30
Concerns About GMOs 9:31
Types of GMOs 11:33
Review & Credits 12:59

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CC Kids:
Have you ever gotten scolded for playing with your food?

Maybe you built a mashed potato volcano, or concocted a “potion”? Yeah, that one didn’t taste very good or give me special powers.

I want my money back. But the thing is: we humans have been playing with our food for thousands of years, and with some pretty amazing results. From seedless watermelons, to bean plants that can survive frigid winters, to regular ol’ broccoli, so much of what we find in the produce section we’ve altered in one way or another.

For as long as humans have grown food, we’ve tinkered with it, trying to make our crops more nutritious, delicious, and resistant to harmful things like disease and drought. And more recently, we’ve figured out how to speed up the process by directly editing plant genes —those tiny units of DNA. Hi!

I'm Alexis, and this is Crash Course Botany. [THEME MUSIC] Our understanding of plant genetics, or how traits get passed down from generation to generation in plants, has developed over thousands of years. From ancient farmers manually pollinating crops to everyone’s favorite 19th-century pea-plant matchmaker and beyond. We now know that organisms pass down traits that make them more likely to survive and reproduce in their environment.

Over time, populations evolve as traits that help them survive are typically selected, and traits that make it harder to survive are usually weeded out. That’s natural selection at work, one of the main drivers of evolution. But long before we knew what evolution was, humans figured out that if we selected plants or animals with traits we liked and got them to reproduce, their offspring would likely have those same traits.

Scientists later dubbed this "artificial selection" because people were actively choosing what traits to pass down. And artificial selection through breeding —or controlling which plants reproduce with which— can lead to dramatic results in just a few generations, compared to natural selection’s millions of years. For example, around four thousand years ago, farmers in the Mediterranean took a leafy weed and bred it with varieties they acquired through trade, encouraging an array of desirable traits.

Eventually, that weed diverged into kale, kohlrabi, cauliflower, collard greens, cabbage, brussels sprouts, romanesco, and broccoli. Yep, those are all different varieties of the same species. It’s artificial selection so extreme that they’re known as the “dog breeds of the plant world.” And today, as climate change affects crops globally, scientists are investigating new — and harnessing old — ways to breed plants that could help stabilize, and even increase, our food supply.

Like, in Mexico, Indigenous farmers have been breeding spineless cacti for centuries as a drought-tolerant crop to feed livestock. But now, these cacti are also being grown by farmers in Eastern Africa and the Middle East, where climate-change-induced drought has hit hard. And similar strategies are being used all over the world to breed more resilient staples of the human diet, too.

Beneficial traits like drought tolerance are caused by specific genes encoded in a plant’s DNA — which is basically its molecular instruction manual on how to be a plant. But when you breed plants, you’re mixing all their genes together, so it can take a really long time to get the combination you’re looking for. We don’t all have years to spend in a monastery garden playing with pea plants.

So, to complement plant breeding, scientists have developed new biotechnology tools— which are exactly what they sound like: technological inventions using living things. Like, thanks to DNA-sequencing technology, we’re able to identify the specific genes that cause certain traits, and target our efforts more precisely. And a major tool in the biotech toolbox is genetic modification.

A genetically modified organism, or GMO, is any living thing that’s had its DNA changed in some way. Chances are you’ve heard of GMOs before, maybe on the news or on the “NON-GMO” packaging of different foods, like popcorn, yogurt, and Grape-Nuts. Am I the only one who likes Grape-Nuts?

And just like any new technology, people have lots of questions. We all want to know if what’s going into our bodies is healthy and safe. And the idea of tweaking our food’s DNA in a lab can make some people feel uneasy.

Like, if we eat GMOs, will we suddenly inflate into a huge, green superhero and want to Hulk-Smash everything in our path? The short answer is no. While biologists do make GMOs in a lab, the way they do it is actually sort of… natural.

They use organisms that have naturally evolved a way to genetically modify plants. Like, Agrobacterium — Agro for short — is a type of bacteria that can make GMOs. When Agro infects a plant, it inserts its own genes into the plant’s DNA.

Those genes basically instruct the plant to produce a big house and lots of food for the Agro. But scientists figured out they could remove the Agro’s genetic instruction and replace it with a different genetic instruction — one that makes a plant resistant to disease or produce more nutrients. Then, the Agro inserts those beneficial genes into the plant’s DNA instead.

After the Agro has done its job, the scientists can remove it, because the plant is now able to pass down its modified genes (along with all of its original genes) to its babies, same as any other plant. Another natural genetic modification tool we use in the lab is called CRISPR, which we borrowed from a different species of bacteria. It’s basically part of the bacteria’s immune system — it remembers DNA sequences from attacking viruses and chops them up in specific places.

But we can tell it to chop up plant DNA instead —or the DNA of other organisms— which allows us to use CRISPR as a super-precise gene editor. Basically, it lets us change, add, or remove genes. This may seem like new-fangled technology, but it turns out that we’ve been eating GMOs for a very long time.

Like, thousands of years. Let’s go to the Thought Bubble… Welcome to the International Potato Center, headquartered in Lima, Peru, whose vision is “a healthy,  inclusive, and resilient  world through root and tuber systems.” I need that on a t-shirt. In 2015, scientists at the Center were examining sweet potato DNA sequences, when they stumbled upon some genes that were distinctly un-potato-like— genes from Agrobacterium!

At first, the team thought the Agro genes in the sweet potatoes might have been from a recent infection. But when they tested the DNA of hundreds of sweet potato varieties from around the world, they found the Agro genes in all of them. This indicated it was actually the ancestor of all those potato varieties that got infected by the bacteria eight thousand years ago.

And then, that ancestor passed the Agro genes down to its offspring. On top of that, they found that the Agro genes were only present in domesticated sweet potato varieties but not in their closest wild relatives. That suggests that the bacterial genes may have actually caused the potatoes to be more desirable to ancient farmers.

These farmers probably intentionally selected the Agro-infected potatoes for breeding because they all had a certain trait that made them extra tasty. The potato scientists are still working on identifying exactly what traits the Agro genes control in the sweet potato, but they think the original infection may have caused the roots to swell up and get extra potatoey and delicious. I, for one, cannot wait to see the fruits — uhh, the roots — of their labor.

Thanks, Thought Bubble! So, it turns out that plants have been ahead of us in the GMO game for millennia —we just didn’t know it! And this reflects the scientific consensus that GMOs are safe to eat.

All plants contain DNA, regardless of their genetic modification status. The only difference is that in a genetically modified plant, scientists have made a few changes to the plant’s DNA. And scientists know exactly what those genetic changes are and what they do because they spend years confirming and analyzing their results through experimentation and peer review.

And one thing GMOs definitely don’t do is modify your genes if you eat them. Plus, before GMOs ever reach the grocery store, they go through years of trials and tests to ensure their safety and efficacy, and they’re highly regulated by government entities across the globe. At this point, GMOs have been used widely for decades, so we have loads of data supporting they’re safe for humans and livestock to eat.

But as with any new technology, there are new challenges. There are tons of different things to consider when adopting a new strategy for something as ancient as farming. Take Golden Rice, a biofortified crop, or a type of plant that’s enhanced for better nutritional value.

It has a gene from corn and a gene from a bacterium that allow it to produce tons of beta-carotene, which in turn produces Vitamin A. Vitamin A deficiency is responsible for blindness and death in millions of children annually, so this crop has the potential to alleviate a major cause of global malnutrition. But it’s one thing to invent a super-powered plant.

It’s another to feed the world with it. And that takes much more than botanical research to make happen —there’s also politics, economics, culture, environmental effects, and a lot more. For example, if a large corporation patents—and therefore owns— a particular strain of genetically modified seeds, that can have harmful financial effects on small farmers who have to pay for licenses to plant the seeds each year.

And it can give that company potentially dangerous control over the global food supply. There’s lots more on the social and political aspects of GMOs in Crash Course Geography. Another concern is about pest-resistant GMOs — that they can stop working over time.

New strains of insects start to emerge that can eat the crops without being poisoned. And that can lead to a whole lot of food being lost to pests that farmers thought couldn’t harm their crops. There’s also a chance that GMOs could begin cross-breeding with and outcompeting non-GMOs for access to resources, and that could lead to less diversity in the species’ gene pool.

Which is a big deal because genetic diversity helps organisms adjust to different environmental conditions and become less vulnerable to disease. On top of that, GMOs may outcompete neighboring plants, potentially causing other species to die out. Scientists and regulators are working on solutions to these possible issues, and new research is being done all the time.

But there are lots of extraordinary things we can do with GMOs already: We can create transgenic plants, which have genes derived from a different species. Like, a group of researchers in Germany studied the Artemisia annua plant, which produces a little bit of a drug that combats malaria. They developed a way to insert its genes into tobacco plants, which are more plentiful and can produce much more of the drug.

This could make the medicine way cheaper and more accessible. Then there are cisgenic modifications that insert a gene from the same or similar species. For example, there’s a disease called apple scab that’s threatening orchards.

Scientists have discovered a resistance gene in a not-so-tasty apple. But, they can insert the resistance gene into a tasty variety, creating a cisgenic apple that’s protected from the disease. Researchers can also create subgenic modifications, which don’t involve the addition of new genes, but edit existing genes instead.

Like, scientists in China recently used CRISPR to make a subgenic modification in wheat — they turned off three genes that repress the wheat’s immune response to a nasty fungal infection. And that change made the wheat better at fighting the infection. So, while we humans have been breeding plants to suit our needs for millennia, genetic modification can allow us to make crops that are even more nutritious and resilient.

And hey, if we keep playing with our food, who knows what other amazing technologies we’ll come up with? Next time, we’ll be learning about how plants relate to each other in their communities, and how ecologists and plant lovers are saving plant species from extinction. Hey, before we go, let’s branch out!

A new GMO pineapple that recently hit grocery store shelves has fruit that is what color? [sings] Get the party started in the comments right now! Thanks for watching this episode of Crash Course Botany which was filmed at the Damir Ferizović Studio and made in partnership with PBS Digital Studios and Nature. If you want to help keep Crash Course free for everyone, forever, you can join our community on Patreon.