Scientists unlock key to breeding 'carbon coupling’ plants with a bigger appetite

Discovering how a crucial enzyme „hidden on nature’s map” works sheds new light on how cells control key processes in carbon fixation that are fundamental to life on Earth.

The discovery, made by scientists from the Australian National University (ANU) and the University of Newcastle (UoN), could help engineer climate-resilient crops capable of more efficiently absorbing carbon dioxide from the atmosphere, and producing more food in the process.

research, Published Inside Scientific advancesIt demonstrates a previously unknown function of an enzyme called carboxysomal carbonic anhydrase (CsoSCA), found in cyanobacteria, also known as blue-green algae, to enhance the microbes’ ability to extract carbon dioxide from the atmosphere.

Cyanobacteria are commonly known for their toxic blooms in lakes and rivers. But these tiny blue-green bugs are widespread and live in the world’s oceans.

Although they pose a danger to the environment, researchers describe them as „little carbon superheroes.” Through the process of photosynthesis, they play an important role in sequestering 12% of the world’s carbon dioxide every year.

The first author and Ph.D. Researcher Sacha Bulsford from ANU describes how efficient these microbes are at capturing carbon.

„Unlike plants, cyanobacteria have a system called the carbon dioxide concentration mechanism (CCM), which allows them to fix carbon from the atmosphere and convert it into sugars at a significantly faster rate than standard plants and crops,” Ms. Pulsford said.

At the heart of the CCM are large protein compartments called carboxysomes. These structures are responsible for sequestering carbon dioxide, housing CsoSCA and another enzyme called Rubisco. CsoSCA and Rubisco enzymes act synergistically, demonstrating the highly efficient nature of CCM. CsoSCA creates a high local carbon dioxide concentration within the carboxysome, which Rubisco then absorbs and turns into sugar for the cell to consume.

Lead author from UoN, Dr. Ben Long, „Until now, scientists did not know how the CsoSCA enzyme is regulated. Our study focused on unraveling this mystery, particularly in a large group of cyanobacteria found around the world. What we found was completely unexpected. .

„The CsoSCA enzyme dances to the tune of another molecule called RuBP, which turns it on like a switch. Think of photosynthesis as a sandwich. Carbon dioxide fills in from the air, but a photosynthetic cell has to provide bread. And that’s RuBP. Just like you need bread to make a sandwich, The rate at which carbon dioxide is converted to sugar depends on how fast RuBP is supplied.

„How fast the CsoSCA enzyme delivers carbon dioxide to Rubisco depends on how much RuBP is present. When there is enough, the enzyme is turned on. But if the cell lacks RuBP, the enzyme is turned off, making the system highly tuned. And surprisingly, the CsoSCA enzyme is embedded in nature’s blueprint. , it’s just waiting to be discovered.”

Engineered crops that are more efficient at sequestering and using carbon dioxide could provide a major boost to the agricultural industry by greatly improving crop yields while reducing the need for nitrogen fertilizer and irrigation systems, scientists say. It will also ensure that the world’s food systems are more resilient against climate change.

Ms Pulsford said, „Understanding how the CCM works will not only enrich our knowledge of the natural processes underlying Earth’s biogeochemistry, but can guide us in developing sustainable solutions to the greatest environmental challenges facing the world.”