With A Genetic Tweak, Crops That Grow 40 Percent Larger

tractor spraying crops

(Credit: Fotokostic/Shutterstock)

What if your ability to feed yourself was dependent on a process that made a mistake 20 percent of the time?

We face this situation every day. That’s because the plants that produce the food we eat evolved to solve a chemistry problem that arose billions of years ago. Plants evolved to use carbon dioxide to make our food and the oxygen we breathe – a process called photosynthesis. But they grew so well and produced so much oxygen that this gas began to dominate the atmosphere. To plants, carbon dioxide and oxygen look very similar, and sometimes, plants use an oxygen instead of carbon dioxide. When this happens, toxic compounds are created, which lowers crop yields and costs us 148 trillion calories per year in unrealized wheat and soybean yield – or enough calories to feed an additional 200 million people for a whole year.

Improving crop yields to grow more food on less land is not a new challenge. But as the global population grows and diets change, the issue is becoming more urgent. It seems likely that we will have to increase food production by between 25 and 70 percent by 2050 to have an adequate supply of food.

As a plant biochemist, I have been fascinated by photosynthesis for my whole career, because we owe our entire existence to this single process. My own interest in agricultural research was spurred by this challenge: Plants feed people, and we need to quickly develop solutions to feed more people.

tobacco plants

Amanda Cavanagh tests modified tobacco plants in a specialized greenhouse to select ones with genetic designs that boost the yield of key food crops. (Credit: Claire Benjamin/RIPE Project, CC BY-ND)

Supercharging Photosynthesis to Grow More Food

It can take decades for agricultural innovations such as improved seeds to reach growers’ fields, whether they are created via genetic approaches or traditional breeding. The high-yielding crop varieties that were bred during the first green revolution helped prevent food shortages in the 1960s by increasing the proportion of grain-to-plant biomass. It’s the grain that contains most of the plant’s consumable calories, so having more grain instead of straw means more food. But most crops are now so improved that they are close to their theoretical limit.

I work on an international project called Realizing Increased Photosynthetic Efficiency (RIPE), which takes another approach. We are boosting harvests by increasing the efficiency of photosynthesis – the solar-powered process that plants use to turn carbon dioxide and water into greater crop yields. In our most recent publication, we show one way to increase crop yield by up to 40 percent by rerouting a series of chemical reactions common to most of our staple food crops.

Photorespiration Costs a Lot of Energy

Two-thirds of the calories we consume across the globe come directly or indirectly from just four crops: rice, wheat, soybean and maize. Of these, the first three are hindered by a photosynthetic glitch. Typically the enzyme that captures carbon dioxide from the atmosphere, called Rubisco, converts carbon dioxide into sugar and energy. But in one out of every five chemical reactions, Rubisco makes a mistake. The enzyme grabs an oxygen molecule instead. Rather than producing sugars and energy, the chemical reaction yields glycolate and ammonia, which are toxic to plants. To deal with this problem, plants have evolved an energy-expensive process called photorespiration that recycles these toxic compounds. But toxin recycling requires so much energy that the plant produces less food.

photosynthesis

In the process of photosynthesis, carbon dioxide and water are transformed into sugars and oxygen. Sunlight powers this chemical reaction. (Credit: BlueRingMedia/Shutterstock)

Photorespiration uses so much energy that some plants, like maize, as well as photosynthetic bacteria and algae, have evolved mechanisms to prevent Rubisco’s exposure to oxygen. Other organisms, like bacteria, have evolved more efficient ways to remove these toxins.

These natural solutions have inspired many researchers to try to tweak photorespiration to improve crop yields. Some of the more efficient naturally occurring recycling pathways have been genetically engineered in other plants to improve growth and photosynthesis in greenhouse and laboratory conditions. Another strategy has been to modify natural photorespiration and speed up the recycling.

Chemical detour improves crop yield

photosynthesis pathway

The red car represents unmodified plants who use a circuitous and energy-expensive process called photorespiration that costs yield potential. The blue car represents plants engineered with an alternate route to shortcut photorespiration, enabling these plants to save fuel and reinvest their energy to boost productivity by as much as 40 percent. (Credit: RIPE, CC BY-SA)

These direct manipulations of photorespiration are crucial targets for future crop improvement. Increased atmospheric carbon dioxide from fossil fuel consumption boosts photosynthesis, allowing the plant to use more carbon. You might assume that that this will solve the oxygen-grabbing mistake. But, higher temperatures promote the formation of toxic compounds through photorespiration. Even if carbon dioxide levels more than double, we expect harvest yield losses of 18 percent because of the almost 4 degrees Celsius temperature increase that will accompany them. We cannot rely on increasing levels of carbon dioxide to grow all the food we will need by 2050.

I worked with Paul South, a research molecular biologist with the U.S. Department of Agriculture, Agricultural Research Service and professor Don Ort, who is a biologist specializing in crop science at the University of Illinois, to explore whether modifying the chemical reactions of photorespiration might boost crop yields. One element that makes recycling the toxin glycolate so inefficient is that it moves through three compartments inside the plant cell. That’s like taking an aluminum can into three separate recycling plants. We engineered three new shortcuts that could recycle the compound in one location. We also stopped the natural process from occurring.

modified plants experiment

Four unmodified plants (left) grow beside four plants (right) engineered with alternate routes to shortcut photorespiration. The modified plants are able to reinvest their energy and resources to boost productivity by 40 percent. (Credit: Claire Benjamin/RIPE Project, CC BY-ND)

Designed in Silico; Tested in Soil

Agricultural research innovations can be rapidly tested in a model species. Tobacco is well-suited for this since it is easy to genetically engineer and grow in the field. The other advantage of tobacco is that it has a short life cycle, produces a lot of seed and develops a leafy canopy similar to other field crops so we can measure the impact of our genetic alterations in a short time span. We can then determine whether these modifications in tobacco can be translated into our desired food crops.

We engineered and tested 1,200 tobacco plants with unique sets of genes to find the genetic combination that recycled glycolate most efficiently. Then we starved these modified plants of carbon dioxide. This triggered the formation of the toxin glycolate. Then we identified which plants grew best – these have the combination of genes that recycled the toxin most efficiently. Over the next two years, we further tested these plants in real-world agricultural conditions. Plants with the best combination of genes flowered about a week earlier, grew taller and were about 40 percent larger than unmodified plants.

Field Trials

Over two years of field trials, scientists Donald Ort (right), Paul South (center) and Amanda Cavanagh (left) found tobacco plants engineered to modify photorespiration are more productive in real-world field conditions. Now they are translating this technology hoping to boost the yield of key food crops, including soybeans, rice, cowpeas and cassava. (Credit: Claire Benjamin/RIPE Project, CC BY-ND)

Having shown proof of concept in tobacco, we are beginning to test these designs in food crops: soybean, cowpea, rice, potato, tomato and eggplant. Soon, we will have a better idea of how much we can increase the yield of these crops with our modifications.

Once we demonstrate that our discovery can be translated into food crops, the Food and Drug Administration and the USDA will rigorously test these modified plants to make sure they are safe for human consumption and pose no risk to the environment. Such testing can cost as much as US$150 million and take more than 10 years.

Since the process of photorespiration is common across plant species, we are optimistic that our strategy will increase crop yields by close to 40 percent and help find a way to grow more food on less land to be able to feed a hungry global population by 2050.

 

Amanda Cavanagh, Postdoctoral Research Associate at the Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The Conversation

CATEGORIZED UNDER: Environment, Living World, Top Posts
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  • http://www.mazepath.com/uncleal/EquivPrinFail.pdf Uncle Al

    Famine has been ended. This is a political global disaster. What can we do to put the genie back into the bottle…and weld it shut?

  • Thomas Palm

    If this change is so superior, how do you make sure you don’t create a superweed that spreads uncontrollably? Possibly by cross fertilization with wild relatives to your cultivated plant.

    • http://www.mazepath.com/uncleal/EquivPrinFail.pdf Uncle Al

      It is better that a billion people starve than one poppy, marijuana, or cocaine field suffer labor-intensive weeding. That’s agrarian slavery!

      • Thomas Palm

        I don’t worry so much about plants growing on the wrong field, but that they spread uncontrollably in the wild. It’s bad enough with natural plants or animals that are moved to a new area where they thrive more than expected wiping out the local flora.

        • http://www.mazepath.com/uncleal/EquivPrinFail.pdf Uncle Al

          What did “local flora” ever do for you?

          • Erik Bosma

            When a supernova explodes and plants get bombarded with all kinds of mutating radiation that’s evolution and it is good; when scientists mutate plants with the goal of improving the plant that’s manipulation and it’s bad.

  • Mike Richardson

    I realize that many express fears of “Frankenfoods,” super weeds, or other imagined perils of genetically modified foods. However, as this article describes, there are many benefits in terms of production and nutritional value to using what is essentially a short-cut to thousands of generations of selective breeding, or in some cases, creating strains of healthy food sources that would otherwise not be possible. There are legitimate concerns as to testing transgenic crops where food allergies are concerned, or the monopolization of monoculture crops by large agricultural corporations, but overall this technology can greatly benefit humanity. Reducing hunger and improving nutrition for the world’s population have long been worthy goals, and are now aided by genetic engineering technology.

  • OWilson

    While there is a “there is a scientific consensus[6][7][8][9] that currently available food derived from GM crops poses no greater risk to human health than conventional food,[10][11][12][13][14]” and are feeding the world’s hungry, there exists an organized opposition, from the usual suspects, “Advocacy groups such as Center for Food Safety, Union of Concerned Scientists, Greenpeace and the World Wildlife Fund” …. “leading 38 countries, including 19 in Europe, to officially prohibit their cultivation.[2]” Wiki.

    We still have a ways to go to satisfy their concerns, if indeed, they can ever be satisfied.

  • Mr. Tippy Tops

    Great job!

  • okiejoe

    If, on the other hand, we were to stabilize our population and even allow it to drift lower for a couple of generations much of the pressure to produce more would be removed. During that interval we could reinvent our society to be more efficient and less destructive of our planet.

  • nik

    It seems to me, that if the Rubisco process was stopped from making errors in the first place, the it wouldn’t be necessary to correct the errors.
    Fix the cause, not the symptoms.

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