Researchers at Michigan State University in East Lansing have identified a family of genes in cyanobacteria that help control carbon dioxide fixation, furthering knowledge of photosynthesis. The discovery opens new doors to design systems for sustainable biotech production.
Cyanobacteria and plants have an enzyme called rubisco that captures carbon dioxide from the atmosphere. Carbon capture is the first in a series of reactions that turn carbon into high-energy molecules that feed the planet’s organisms.
In plants, rubisco often is blocked from working by small molecules that attach to it. In response, a protein called rubisco activase removes them. Recent advances in bioinformatics have allowed the lab of Cheryl Kerfeld to identify a cyanobacterial gene that looks like the one that encodes plant rubisco activase. The new gene encodes what the lab is calling an activase-like cyanobacterial protein (ALC). It is widespread in many types of cyanobacteria.
The cyanobacterial ALC’s function remains unknown. It doesn’t remove small molecules from rubisco like rubisco activase. Researchers think ALC and rubisco, however, work together in some way because ALC is physically similar to rubisco. Researchers also have evidence that shows ALC evolving with rubisco in cyanobacteria.
“We saw ALC causing rubisco proteins to aggregate,” says Sigal Lechno-Yossef, research assistant professor in the Kerfeld lab. “This function is similar to that of another cyanobacterial protein, which is known to contribute to rubisco regulation and localization in the cell.”
There is also evidence that ALC helps its host detect carbon dioxide levels to adjust photosynthesis rates. When the team got rid of the ALC gene in lab cyanobacterium, the organism did not experience changes in growth. In plants, deleting the rubisco activase causes carbon starvation. The same strains experienced morphological changes, however, when grown in CO2-rich environments.
The research holds promise in the biotech field. Improving rubisco would lead to plants with higher nutrition contents and higher crop yields.
“Cyanobacterial researchers also want to increase energy yield from photosynthesis,” says Lechno-Yossef. “The goal would be to rewire cyanobacteria’s photosynthetic machine to produce renewable energy compounds or materials for use in medicine or industry.
“Now we know that cyanobacteria have an enzyme that supports rubisco, we could try making more robust cyanobacteria for industrial applications.”
The work was published in the journal New Phytologist.