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Hacking photosynthesis, researchers might almost double crop yields

A genetic tweak that makes photosynthesis more efficient in plants could increase crop yields by 40%, and help feed millions more people around the globe.
January 11, 2019

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Researchers writing in the journal Science describe a groundbreaking new way of genetically engineering plants, that could almost double yields in the world’s most important crops.

The technique, which was tested on tobacco plants as a proxy for crops, works by increasing the efficiency of photosynthesis. This enables plants to grow faster and bigger–and ultimately increases their yields by 40%, the study showed.

The scientists on the new study–who are part of an ambitious, long-term international research project called Realizing Increased Photosynthetic Efficiencyestimate that the boosted productivity could help to feed an additional 200 million people in the Midwestern United States alone, if applied to crops grown there. At a global scale, the genetic tweak could assist in feeding billions more people by 2050, they estimate.

Photosynthesis occurs with the help of an enzyme inside plants called RuBisCo, which latches onto molecules of carbon dioxide to convert them into energy-rich sugars for growth. But about a fifth of the time, RuBisCo grabs onto molecules of oxygen instead.

That presents a major lost opportunity for photosynthesis. That’s because oxygen molecules inside plants go on to create waste products, such as glycolate and ammonia. These have to be recycled in a process called photorespiration, otherwise they will harm the plant. But photorespiration involved a convoluted three-part pathway through a plants’ cells that is very energy-intensive. In turn, this “costs the plant precious energy and resources that it could have invested in photosynthesis to produce more growth and yield,” the researchers explain.

In some crops, in fact, photorespiration is estimated to cause a 50% loss in photosynthesis’ efficiency.

But in their investigations, the researchers were able to engineer tobacco plants (which are useful research subjects because they’re easy to genetically modify) to contain a much shorter photorespiration pathway with fewer steps. This saves on energy and crucially, increases the efficiency of photosynthesis, therefore boosting plant growth. In tests that ran for two years, the researchers showed that tobacco plants grown both in the laboratory and under real-world farming conditions consistently grew faster, taller, and had more biomass than their non-engineered counterparts.

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In hot, dry regions of the world this discovery would be especially valuable: under high heat, RuBisCo struggles even more to differentiate between carbon dioxide and oxygen, leading to even more inefficient photosynthesis. These genetic tweaks would provide a useful way around that stumbling block, in countries that already have a high food security risk.

The researchers are careful to caution that their discovery isn’t a quick-fix, however. It will take several years to engineer crops with these energy-saving traits, and also to ensure that they are as safe to eat as their non-engineered counterparts. But with the rising twin challenges of increasing food production to feed billions more people, and doing so on less land to conserve biodiversity, the researchers believe this could be one powerful way of producing food more efficiently and sustainably.

To reach that goal, now they’re focusing on engineering globally-important staple crops such as soybeans, cowpeas, rice, and potatoes, to contain the beneficial traits. “Our goal is to build better plants that can take the heat today and in the future, to help equip farmers with the technology they need to feed the world,” the researchers say.

Source: South et. al. “Synthetic glycolate metabolism pathways stimulate crop growth and productivity in the field.” Science. 2018.
Image: Giphy


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