Researchers put plant protein mechanism into bacteria to help move forward 50 years of effort

RIPE, or Realizing Increased Photosynthetic Efficiency, led by the University of Illinois Urbana-Champaign, is engineering crops to be more productive by improving photosynthesis, the natural process all plants use to convert sunlight into energy and yields. RIPE is supported by the Bill & Melinda Gates Foundation, Foundation for Food & Agriculture Research, and the U.K. Foreign, Commonwealth & Development Office.

This work was undertaken with the goal of understanding and improving Rubisco, the protein in plant chloroplasts that initiates the fixation of atmospheric carbon dioxide into sugars during the process of photosynthesis. Unlike many other proteins in photosynthesis, Rubisco is slow and requires a number of 'chaperones' in order to operate properly. Research over the last few decades has identified most, possibly all, of these partners. This provides scientists with new capabilities to study and speed up plant Rubisco in Escherichia coli, commonly known as E. coli -- a bacteria found in the environment, foods, and human intestines -- and a host often used in science to more quickly study proteins.

In a new article published in the Journal of Experimental Botany, the ANU team demonstrated the utility of a robust, genetically modular, E. coli expression tool. The work builds on a comparable expression tool developed in the Manajit Hayer-Hartl lab to provide a new system better suited for improving Rubisco efficiency.

"Assembling this new bacterial bioengineering strategy and comparing its efficiency relative to natural chloroplasts was a long-term challenge," said Whitney, a Professor in ANU's Research School of Biology. "Thankfully, this new technology now provides us unprecedented experimental through-put with outcomes available within days rather than the months our slow and costly traditional testing approach using plant transgenics would take."

While this new E. coli Rubisco bioengineering system will need additional design tweaks to tailor its compatibility with different crops, Whitney is confident their research provides a critical turning point in being able to tune up Rubisco activity.

"We can now apply the protein optimization tool of Directed Evolution, a tool we have already used to speed up the CO₂-fixation rates in a number of different non-plant forms, to plant Rubisco," said Whitney. "Once we do that, we can introduce the desired changes to speed up Rubisco in crops by gene editing. Then we will see the benefits in photosynthetic performance and the impact on plant growth and yield."