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Solving biology's mysteries with plants

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Paclitaxel is a compound that can treat cancer. Salicylic acid reduces headaches and fevers. Carotenenoids can turn your skin orange. And miraculin changes your sense of taste. What do all of these awesome compounds have in common? They all come from plants. [MUSIC PLAYING] More than 100,000 natural compounds occur in plants, and we've barely explored them. These small molecules are called metabolites. Just like all the DNA in an organism forms the genome, all of the metabolites form the metabolome. Even though each metabolite can be made from only six elements, there are so many possibilities that it would take scientists thousands of years to make each one and figure out its usefulness. Luckily, plants have already done this for us. Plants have the disadvantage of being rooted to the ground. So over time, they've trialed and errored, making lots of compounds to see which ones help them survive and thrive best. And because they've been interacting with other species like us for hundreds of thousands of years, some of their chemicals turn out to be really useful, both inside and outside our bodies. But to use plants to their full potential, we have to know what chemicals they make and how they make them. Instead of studying every chemical one by one, what if we could study all of them at once? We can start by mapping the huge network that connects metabolites. In any living organism, molecules are always on the move, being converted and shuttled, decomposed, and filled back up again and reused. It's just like a subway system, except in biology the people are the chemicals, and the train is the enzyme that converts and moves them. If you look at a city from above, how could you map the whole subway system? Similarly, if we look at a plant, how can we figure out the entire metabolome network? To figure out a path in the system, what we actually need to do is break it. If we mutate or disrupt a pathway and see how the metabolite quantities change, we can figure out the connections between them. Let's say the train from Central to MIT breaks. We wouldn't see students arriving at MIT, and would instead see them building up at Central. But not only that, anyone else traveling along the Red Line would also be affected. So it's the redistribution of people which reveals the Red Line subway path and tells us where the train broke. We can use this system's thinking to uncover the plant metabolite network. For example, we know that a compound called sinapoyl malate, which protects the plant from UV damage by interacting with UV light, making the plant glow green. And without it, the plant would glow red. So if we see a red plant, it's like seeing no people at the sinapoyl malate station. But we wouldn't yet know where the train broke or what other stations are along the route. To do that, we can mutate a lot of the seeds, plant them, and choose the red ones. [MUSIC PLAYING] Now, we can analyze these samples by using the mass spectrometer. It measures how much of each metabolite is present in the sample. Then we can use a program to see which compounds are effective and map that part of the network. It's like revealing the Red Line. Once we figure out how the entire metabolome works, we can use it to engineer plants to create new biomaterials, medicines, and clean energy. We might even discover that plants have the secret to living forever. We just need to unlock their chemical mysteries. [MUSIC PLAYING]