Plants seem to break the rules of biochemistry by making ‘secret decisions’

Researchers have just discovered a previously unknown process that makes sense for the “secret decisions” that plants make when releasing carbon back into the atmosphere.

“We found that plants control their respiration in a way we didn’t expect, they control how much photosynthesis carbon they retain to build biomass using the metabolic channel,” Harvey Millar, a plant biochemist at the University of Western Australia, told ScienceAlert.

“This happens properly as a step before they decide to burn a compound called pyruvate to make and release carbon dioxide2 back to the atmosphere.”

If you were thinking about biology in high school, you might remember that during photosynthesis, plants make sugar, or sucrose. The plant usually produces an excess of sucrose; Some are stored, others are degraded. This is called the citric acid (or carboxylic acid) cycle, and it is equally important for life.

As part of this cycle, sucrose, which has twelve carbons, is broken down into glucose with six carbons. The glucose is then broken down into pyruvate, which contains three carbon atoms. Using pyruvate for energy results in carbon as a waste product, so the “decision” is made at this point in the plant.

“Pyruvate is the final point to make a decision,” Millar told ScienceAlert.

“You can burn it and release carbon monoxide2Or, you can use it to build phospholipids, vegetable oils, amino acids, and other things you need to make biomass. “

This discovery was made while working on a classic plant organism called tali cress (Arabidopsis thaliana). The researchers, led by University of Western Australia plant molecular scientist Xuyen Le, labeled pyruvate with C13 (an isotope of carbon) to track where it was transformed during the citric acid cycle, and found that pyruvate from different sources was used differently.

This means the plant can actually trace the source of the pyruvate and act accordingly, choosing to either release it or stick with it for other purposes.

“We found that a transporter in the mitochondria directs pyruvate into respiration to release carbon dioxide2but pyruvate made in other ways is preserved by plant cells to build biomass — if the transporter is blocked, the plants use pyruvate from other respiration pathways,” Lu said.

“Imported pyruvate was the preferred source for citrate production.”

The team suggests that this ability to make decisions breaks the normal rules of biochemistry, where usually every reaction is competition and processes don’t control where a product goes.

“Metabolic directive breaks these rules by revealing reactions that do not behave as such, but are specific decisions in metabolic processes that are protected from other reactions,” Millar says.

“This is not the first metabolic channel that has ever been found, but it is relatively rare, and this is the first evidence of a channel that controls this breathing process.”

Although plants are wonderful stores of carbon dioxide2 Forests alone store about 400 gigatons of carbon – not every molecule of carbon dioxide2 Which are taken up by plants and then preserved. About half of the carbon dioxide absorbed by plants is released back into the atmosphere.

Being able to get plants to store a little more carbon dioxide in the process might be a great way to help our climate change problems.

“When we think about building and raising plants for the future – we should not only think about how they can be good food and food for our health, but also whether they can be good carbon deposits for the health of the atmosphere that we all have depends on” , Millar told ScienceAlert.

Such a future optimization has yet to come, as researchers have just discovered this biochemical process to be delayed with it. But if we can hijack the way plants make decisions about carbon storage, it could be part of the larger puzzle of mitigating climate change.

The search was published in nature plants.

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