Hacking evolution screening technique may improve most widespread enzyme

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This media release was originally published on the Realising Increased Photosynthesis Efficiency  (RIPE ) website and has been written by Claire Benjamin

Plants evolved over millions of years into an environment that has dramatically changed in the last 150 years since the Industrial Revolution began: carbon dioxide levels have increased 50 percent stimulating a gradual rise in average global temperatures. While natural adaptation has been unable to keep up, scientists have developed tools to simulate millions of years of evolution in days to help plants adapt.

Published by the Journal of Biological Chemistry, researchers report a novel screening strategy that enabled them to identify, for the first time, a much more efficient form of the enzyme Rubisco, which catalyses the first step of fixing carbon dioxide en route to creating plant biomass in photosynthesis.

Rubisco is the most abundant protein on the planet, and you could argue, the most important one, because this enzyme plays an essential role in photosynthesis, the process in which organisms transfer light energy into chemical energy.

“We’ve shown that we can improve Rubisco’s efficiency, its ability to differentiate carbon dioxide from oxygen ––that’s the real buzz,” said lead author Spencer Whitney,  Chief Investigator at the ARC Centre of Excellence for Translational Photosynthesis, at the Australian National University. “Our Rubisco is faster and has a higher affinity for carbon dioxide. In the past, this determination took about two weeks, but our new screening system cut that time more than in half.”

Using directed evolution, often described as evolution in a test tube, the team tested 250,000 mutant Rubiscos from cyanobacteria in E. coli bacteria engineered so their survival depends on the efficiency of the enzyme. “Finding answers on how to improve Rubisco is like looking for a needle in a haystack,” Whitney said. “The beauty of this system is that it allows us to get rid of all those pieces of hay.”

Eighteen Rubisco mutants survived the screen, eleven of which were found to be much more efficient at fixing carbon dioxide. “We found these mutations are localized to a previously unexplored region of this plant like Rubisco” said Dr Robert Wilson, co-inventor of the new system. “Now the hope is to make similar tweaks to improve Rubisco in crops and increase their growth and yield.”

This work was funded by the Australian Research Council Centre of Excellence for Translational Photosynthesis and an Australian Postgraduate Award to Robert Wilson. The research was undertaken in association with the Bill & Melinda Gates Foundation supported Realizing Increased Photosynthetic Efficiency (RIPE) Project.

The paper “An improved Escherichia coli screen for Rubisco identifies a protein-protein interface that can enhance CO2-fixation kinetics” is published by the Journal of Biological Chemistry (doi: 10.1074/jbc.M117.810861). Co-authors include Robert H. Wilson, Elena Martin-Avila, and Carly Conlan.