Superhero Chloroplasts

This week, I bring you another plant-related article, this time discuss how scientists are trying to upgrade the photosynthetic process in plants.


A chloroplast, which, in the future, could be filled with honeycomb-like structure called carboxysomes

It has been a billion years since an eukaryote ingested a chloroplast and by accident created the essential symbiotic relationship to which we owe all the energy by which we survive. However, the way chloroplasts work hasn’t really changed in all these years, even though the environment has, and its system is quite obsolete. On the other hand, the descendants from the species of the first chloroplast, the cyanobacteria, have really changed their photosynthesis, which is much more efficient than that of chloroplasts.

The main difference between our world and the world a billion years ago, at least for this topic, is CO2 and 02 levels in the atmosphere. Before, there was an enormous amount of carbon dioxide in the atmosphere, which cyanobacteria and chloroplasts could exploit to produce food by photosynthesis. But as plants became more abundant, they absorbed the CO2 and released 02 , giving rise to our current balance of elements in the air. The most favourable conditions for a fast photosynthetic rate are high levels of CO2 in the air but since this is not the case anymore, there is a need for some changes in the organisms themselves. Plants, which have remained mostly unchanged, have reduced their efficiency, whereas cyanobacteria, which have evolved, actually improved it. The key to their success lies in their ability to maintain high levels of CO2 within the cell, thanks to carboxysomes. These are tiny, regularly-shaped compartments that fill the bacteria, and are specialised in maintaining CO2 trapped in them, so there is more of it available for photosynthesis. They even have protein pumps in their membrane which actively pumps CO2 into the cell.

This unique mechanism is what scientists are now trying to copy into a normal plant chloroplast. To do so, they would use genetic engineering: adding genes from the marvelous cyanobacteria to the chloroplasts so they would develop the pumps, which could increase efficiency between 15-25%; an outstanding upgrade. Transferring the carboxysome technology would be a bit more complicated, requiring more genes and the knowledge on how to make the structure itself, which at the moment is lacking.

Still, this innovative improvement offers an immense upgrade, which would sure be useful to farmers and food suppliers, who have found a rapid increase in their customer pool but a slow increase in their yield, a problem which could be remedied if this solution worked.

As always, there is some opposition, arguing that if plants have evolved for millions of years and have never developed a new way for photosynthesis to occur, there must be a reason for a reason, so natured shouldn’t be tinkered with. The pros and cons for this situation are many, and it is a subject which divides the scientific community.


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