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Bioengineering corrects photosynthetic errors in tobacco, enabling a 40% crop-yield increase

Engineered photosynthesis boosts crop yields

From an engineering point of view, photosynthesis is inefficient. One out of every five tries, the enzyme that plants use to catch carbon dioxide mistakenly grabs on to oxygen, producing toxic glycolate instead of carbohydrate building blocks. This misstep is called photorespiration. Plants use a tremendous amount of precious energy to correct it. In fact, photorespiration reduces crop yields by an estimated 20 to 50%.

Now researchers have demonstrated a better way to correct this photosynthetic error. Tobacco plants genetically engineered to more efficiently break down glycolate showed 40% greater crop yields in field trials (Science 2018, DOI: 10.1126/science.aat9077). If the findings can be replicated in food crops, farmers could produce more calories using less land and fertilizer.

“This is a demonstration that you can alter photorespiration in a fundamental way and get significant gains in yields—and that’s exciting,” says Berkley Walker, a plant biologist at Michigan State University who was not involved with the research. Walker’s modeling work suggests that if photorespiration were eliminated, farmers in the midwestern US would produce 320 trillion more calories from their crops annually on the same amount of land (Annu. Rev. 2016, DOI: 10.1146/annurev-arplant-043015-111709).

South and his collaborators tested a novel pathway that added a glycolate-processing enzyme from the algae Chlamydomonas and a malate synthase from a pumpkin, and blocked some aspects of native photorespiration.

But researchers still need to determine whether these changes “will also boost productivity in other plant-crop species and in the parts of the plants that are used as food such as seeds, roots, and fruits,” Maurino says. The Illinois group is now trying to engineer this pathway into soy and plants that are major sources of calories in the developing world, including cassava and cowpeas.

abstract...

Synthetic glycolate metabolism pathways stimulate crop growth and productivity in the field

Numerous homozygous transgenic lines increased biomass productivity by >40% in replicated field trials. These results show that engineering alternative glycolate metabolic pathways into crop chloroplasts while inhibiting glycolate export into the native pathway can drive increases in C3 crop yield under agricultural field conditions.