Scientists correct critical photosynthesis problem, boosting crop growth by 40%

Scientists corrected a natural defect in photosynthesis and thus increased plant productivity by 40% relative to wild relatives.

Photosynthesis is the chemical reaction that allows plants to turn sunlight and carbon dioxide into food. This new hacking could generate enough calories to help feed another 200 people. million people on our planet, from the same volume of cultures.

At present, the fix has been applied only to tobacco plants. We are therefore far from using it to improve our food supply. But it's an incredibly promising first step.

So, what is this "problem" that needs repair? This is a little known step of photosynthesis called photorespiration.

"We could feed more than 200 million people each year with calories lost due to photorespiration in the US Midwest," said principal investigator Donald Ort of the Carl R. Woese Institute of Genomic Biology. from the University of Illinois.

"Getting even some of those calories back into the world would go a long way towards meeting the fast-growing food demand of the 21st century."

To understand what's wrong, you need to understand a little about the random process of evolution. In the immortal words of Dr. Ian Malcolm in the classic science fiction Jurassic Park, "Life finds a way". What he did not say is sometimes so that it is an inefficient hot mess.

To be fair, evolution does what it can under the circumstances. As a graduate student who keeps an eye on summer vacations, he is doing just enough to succeed. What's more is a wasted effort, after all.

For many plants, including rice and soy, it is a simple pass for photosynthesis. We speak a C-.

One of the most clumsy parts is a key step involving the enzyme ribulose-1,5-bisphosphate carboxylase-oxygenase (RuBisCO), which binds a carbon dioxide to the ribulose-1,5-bisphosphate compound (RuBP).

In about 20% of cases, RuBisCO confuses oxygen with the carbon dioxide molecule, an extremely important fact (fun fact: RuBisCO is widely regarded as the most abundant protein on the planet).

Not only is this opportunity wasted, but glycolate and ammonia are two toxic effects that need to be addressed quickly to avoid causing too much damage.

Fortunately, plants have come up with a way to get rid of this poison, called photorespiration. It does not bother them to devote some of their energy to this vital recycling process if it allows them to survive.

But when it comes to cultivating them as a source of food, we certainly do.

"It costs the plant energy and valuable resources that it could have invested in photosynthesis to produce more growth and yield," says lead author and molecular biologist Paul South. of the Agricultural Research Service of the United States Department of Agriculture.

Rice, wheat and soy all suffer from this need to eliminate any toxic buildup. Not only are these three of the world's four most energy-rich crops, but their returns may be expected to decline in the future as a result of global warming.

"RuBisCO has even more difficulty extracting carbon dioxide from oxygen when it's warmer, which causes more photorespiration," said Amanda Cavanagh, co-author of the University. from Illinois.

Over the years, many efforts have been made to find ways to force plants to avoid the need for detoxification.

Many of them involved the discovery of the most effective photorespiration methods adopted by other organisms, including various algae and bacteria.

This last effort is called Achieving increased photosynthetic efficiency (RIPE). His approach was to select genes from elsewhere and test them.

A handful comes from the bacteria E. coli oxidation route of glycolate. A second version used a catalase gene also derived from E. coliand some for a glycolate oxidase and a malate synthase of plants.

Topic # 3 used a plant-derived malate synthase gene and a green-algal gene for glycolate dehydrogenase.

These have been used in conjunction with other genetic modifications to find the most energy efficient route among 17 different constructions.

The third path of photorespiration is that which emerges from the final ranking, the metabolic activity increasing by more than 40% compared to the controls. This gained energy translates into higher returns.

It remains to be seen whether these same efficiencies will be applied to other cultures, but researchers are working on them.

Life does not always find a way. But if we want to get food where it is needed in the future, science will have to do it.

This research was published in Science.

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