And, well, it worked remarkably well. Plants carrying all the MCG cycle genes weighed two to three times more than control plants that had only a few genes. They had more leaves, the leaves themselves were larger, and the plants produced more seeds. Under a variety of growing conditions, plants with an intact MCG cycle incorporated more carbon, and they did so without increasing their water intake.
The two-carbon production result also worked as expected. By feeding the plants radioactive bicarbonate, they were able to track the carbon that appeared in the expected molecules. And imaging confirmed that the plants were making so many lipids that their cells were forming internal pockets containing nothing but fatty material. Triglyceride levels increased by a factor of 100 or more.
So, by various measures, the plants actually did better with the extra pathway for carbon fixation. There are a few caveats, though. For starters, it’s not clear whether what we’re learning from the tiny weed Arabidopsis is currently the same. It could be that the excess fat globules floating around the cell are a consequence of something similar to a tree. Lab-grown plants also tend to be provided with nutrient-rich soil, and it’s not clear whether all of this applies to a range of real-world conditions.
Finally, we can’t say whether all the excess carbon that these plants didn’t suck up from the atmosphere will eventually be sequestered in any useful way. It could be that all the fat will simply be oxidized once the plant dies. However, there are many approaches to making biofuels that rely on modifying fats found in plants or algae. It’s possible that this could eventually help make biofuels efficient enough to actually have a positive impact on the climate.
Regardless of the practical implications, it’s still quite amazing that we’ve now reached a point where we can fundamentally retrace a bit of metabolism that’s been going on for billions of years without completely dismantling plants.
Science, 2025. DOI: 10.1126/science.adp3528 (About Dois).
