The enzyme rubisco is vital for photosynthesis, the process plants use to turn carbon dioxide into sugar. Without it, life on Earth as we know it would not exist. However, rubisco is not very efficient. It often reacts with oxygen instead of carbon dioxide, which wastes energy and slows plant growth. This problem gets worse as temperatures rise.
Hornwort's Secret Weapon
Scientists have found a solution in the humble hornwort, a small plant related to mosses. It's the only known land plant that has found a way to make rubisco work better. It does this by concentrating carbon dioxide around the enzyme.
An international team of scientists has now figured out how hornwort achieves this. They believe they can apply this discovery to common crops. This could lead to much higher yields, meaning farmers could grow more food on less land.
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Start Your News DetoxRobert Wilson, a biochemist at MIT, called the discovery "very impressive." He noted it's a completely new way to improve rubisco's function.
Learning from Algae
Scientists already knew that some algae species also make rubisco more efficient. These algae have special compartments called pyrenoids inside their cells. Pyrenoids concentrate carbon dioxide around rubisco, stopping it from reacting with oxygen. Laura Gunn, a plant biologist at Cornell University and co-author of the new research, explained that pyrenoids essentially "put rubisco into a house" and fill it with CO2, keeping oxygen out.
However, algae are very different from the crops we eat, making it hard to genetically modify crops to have pyrenoids like algae. Hornworts, on the other hand, are more closely related to food crops.
Researchers found that hornworts create these pyrenoid structures using a unique protein called RbcS-STAR. This protein has an extra "tail" that helps link rubisco enzymes together. This creates compartments that pump in CO2, making the process more efficient.
Applying the Discovery to Crops
The researchers introduced the RbcS-STAR protein into a related hornwort species that doesn't naturally have pyrenoids. The rubisco in this species then reorganized to form these compartments. They also tested this with Arabidopsis, a common lab plant, and saw the same result.
Fay-Wei Li, a plant biologist at Cornell University and co-author, said this is a crucial step toward engineering better photosynthesis. The team now plans to genetically modify crops. Gunn believes adding pyrenoid structures could boost crop growth and yields by as much as 60 percent.
Future Benefits for Agriculture
The researchers have built the basic structure for these pyrenoids. The next step is to create the "HVAC system" that pumps CO2 in and sugar out.
If successful, this breakthrough could greatly benefit farmers. Because rubisco is so inefficient, plants need a lot of it. This often requires large amounts of synthetic fertilizers, which are expensive and harmful to the environment. More efficient rubisco could reduce the need for these chemicals.
The discovery could also mean crops use less water. Plants have small openings called stomata to take in CO2. Inefficient rubisco means plants need to open their stomata wide, releasing a lot of water vapor. If rubisco is more efficient, plants can close their stomata more often, saving water.
While algae and hornworts have found ways to improve rubisco, most other plants haven't. This might be because rubisco evolved when there was less oxygen in the atmosphere, so plants didn't need to worry about oxygen interfering.
Scientists are optimistic that improvements to crop yields through plant synthetic biology will happen within the next 10 years. This is a goal the field has pursued for decades.
Deep Dive & References
A hornwort-specific pyrenoid protein is required for carbon dioxide concentration - Science, 2024
