Evolution Update

Evolution Update

Evolution in a Box: Farmers Directing the Evolution of Rice

Noris Sola April 1, 2015

Scientists analyze how farmers have been artificially evolving rice for agricultural benefits.

When we think of artificial evolution, we tend to think of lab work. In my last article, we continued our exploration of that world, focusing on culture and behavior in birds. Even though the birds were released into the wild, their training took place in the lab. But what about artificial evolution that is in nature? This may seem paradoxical, but today we'll explore artificial evolution that can - and does - happen outside the lab.

Farming is one of the biggest and oldest industries in the world. For thousands of years, farming techniques have allowed us to settle and grow, create cities, cultures, and vast civilizations. Another aspect of farming that people tend to forget is that it is the world's first example of artificial evolution.

We have taken plants of all kinds and made them not only edible, but delicious! In the experiment we will discuss today, scientists looked at the cultivation of rice, and how it has changed over time to grow in different areas. To do this they examined the rice genome- its DNA. In addition, these researchers studied the differences between different types of rice. Instead of putting changes in the genome in a lab, someone else had already changed the plant DNA: The farmers who cultivated the rice.

Farming revolutionized the way humans lived. It allowed them to stay in one place for a long time with a predictable food yield; this, in turn, allowed humans to create a stable social structure and provide the nutrition needed to feed large amounts of people. When we look at a piece of fruit or a grain of rice most of the time, we do not think of genetic engineering or evolution. We think of flavour, or how to cook it, or how hungry we are. Usually this last option, because why else would you be staring at food if not to eat it? Maybe if you’re staring at a still-life painting, but other than that - food is on your mind for eating. But in its purest form, farming is all artificial evolution, specifically artificial selection.

Think of a banana. Yellow, fits in your hand, has no seeds and tastes delicious (to some). Would it surprise you to know that originally bananas were a bit more similar to Cacao (the plant use to make chocolate)? Wild bananas grow in round pods with huge seeds that are inedible. You need to break open the hard flesh and eat around the seeds to get to the 'Banana' part. Farmers chose to breed only from the plants that had more flesh and smaller seeds, for hundreds of years, until you got the banana we see today. So what about rice?

Rice looks mostly the same across countries. If you buy a bag of white rice in Japan, China, Italy, or the United States, it will all look, feel, and taste fairly similar. But while the grain may be the same, depending on where it’s grown, the plant that produced it will not be.

Scientists looked at specific genes that have fascinating names like Heading Date 1 (HD1), Early Heading Date 1 (EHD1), and Rice Flowering Locus T 1 (RFT1) that all regulate when rice flowers. Rice generally matures and is ready to be picked in the summer. The plant knows when it is summer because genes like HD1, EDH1, and RFT1 react to changes in sunlight periods during different seasons. Plants use sunlight to grow, but not only because it produces food. They grow because they know when there is more sunlight, less sunlight, and can tell when period such as winter or summer are coming. Changes in the amount of sunlight, temperature, and the type of environment send signals cascading through the plant, telling its cells what to do.

The scientists studied different rice of the same species across different regions of Italy. They sequenced the DNA using a technique called Polymerase Chain Reaction (PCR) to look at specific genes. This method allowed them to see how the isolated genes were different. PCR takes a small sequence of DNA and copies it millions of times while a machine reads each copy. This process informs the scientists of what the sequence is.

They found that the plants had been evolved to contain different changes in HD1, EHD1, RFT1, and a few other genes to help them adapt to their environment. Many of these plants flowered and matured in a completely different environment than from where they had been originally imported. Some grew in cooler climates, other in drier climates, some had been adapted to grow atop mountains, when rice is generally grown in a valley. Scientists concluded that the changes in the way the plants matured allowed rice to be not only cultivated in Europe, but to expand its production further.

It may seem strange to study specific changes in specific genes of one farm plant, especially one that humans have have made such an essential staple of their diets for such a long time.

In general, when a plant such as rice is exported to farmers all over the world their genome changes slightly over the years. Variations to help them grow in specific climates, adapt to different weather and temperatures, all of these variations are selected by the farmer over years of growing the same crop. While adaptation is common, domesticated plants do not carry the diversity that wild plants do because farmers continue to grow from the same set of plants. Think about how most animals reproduce: their genetic material gets mixed with other genetic material to form offspring with different, but very similar genes. Farm plants do not get this advantage. They grow from one plant, over many many years, often accumulating the same genes. This is their biggest weakness. Humans need these farmed plants to possess diversity, so if an infection wipes out a large population, it can be potentially catastrophic.

Studying these changes helps us better understand how plants survive in different environments and what makes them strong. Not only that, but in sequencing the genome of these plants scientists create a record of them. This record can later be referenced to understand further changes to rice’s genome and how and when they occurred. But the real 'scientists' here are the farmers. They have developed techniques to artificially evolve plants, helping them become a worldwide phenomenon. Gregor Mendel first discovered and described genes within plants, using peas to mark and follow different traits and understand how we inherited traits from our parents. Now we look to farms and farmers to further understand genetic changes, how traits are developed, and how they can help humanity grow.

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