Plant & zo
The science of plants and more
A glimpse from the past
Photosynthesis, turning CO2 into sugars, that is something plants are good in, or not? True, plants can do this. We even recognise it as one of the major feats of plants. But to say that they can do it extremely well, not really. For plant scientist like to see if they can improve photosynthesis. If they can, they can improve crop yield with it.
Rubisco is the actual enzyme that turns CO2, with help of sunlight, into sugar. The problem is that it is just as likely to use O2 than CO2 in this reaction. Not really effective. This was not always the case. About 2.5 billion years ago, when Rubisco had just turned up, there was hardly any O2, and Rubisco was much more effective. Since then, Rubisco kept adjusting itself to less CO2 and more O2 in the air. However, it slowed Rubisco down. Now the amount of CO2 in the air increases again, Rubisco can no longer benefit from this, it stays slow. American researchers wanted to know, what it is that made the Rubisco from the past faster. And set out to find out how this Rubisco looked.
The researchers started their search by making a family portrait of current Rubisco variants. They narrowed this down to the nightshade plant family. This is the family tomato, aubergine, pepper, potato, and tobacco belong to. And just like you are not an exact copy of your siblings and cousins but do look like them, the Rubisco proteins of the nightshade family are alike but have differences as well.
The next step was to use this information to find out how the common ancestor of the Rubisco protein of the nightshade family looked like. For this the researchers first made a family tree of the nightshade family. Just like you look more like your siblings than your cousins, tomato and aubergine Rubisco look more alike than tobacco Rubisco. Now the researchers could predict how the Rubisco of the common ancestor of tomato and aubergine Rubisco looked like, and subsequently the one from tomato, aubergine, and tobacco. You can compare this with predicting how your parents look using photos from you and your siblings. And for predicting how your grandparents look, by also using the photos of your cousins.
This gave the researchers portraits of 98 possible historic Rubisco proteins. These proteins were tested to check if they indeed functioned as Rubisco proteins. Which they did, and some of them were even quicker that the currently know variants of Rubisco. Which is exciting, as the researchers might be able to use those to give plants a more efficient Rubisco, so they can grow better.
But historic Rubisco had another surprise for the researchers. Normally when they look to what makes an enzyme more or less effective, the researchers look at where the enzymatic reaction takes place. But this is not where the historic Rubisco is different. It turns out, there are more places on the enzyme that influence the reaction. As it turns out, we can still learn from the past.
Myat T. Lin, Heidi Salihovic, Frances K. Clark, and Maureen R. Hanson (2022) Improving the efficiency of Rubisco by resurrecting its ancestors in the family Solanaceae. Science Advances Vol 8, Issue 15 DOI: 10.1126/sciadv.abm6871