In the recent study, “Improving the Efficiency of Rubisco by Resurrecting Its Ancestors in the Family Solanaceae,” Cornell researchers, Myat Lin, lead author and researcher in the Hanson Lab, and Maureen Hanson, senior author and principal investigator, proposed that photosynthesis efficiency can be increased by 25 percent in common crop plants through the manual integration of an altered Rubisco enzyme into plant cells.
This study demonstrated that varying Rubisco enzymes — the plant’s first step in fixing carbon dioxide from the atmosphere to produce energy — generated different levels of efficiency in plants, with most being nonoptimal for the current level of carbon in the atmosphere.
“[Rubisco] has been known for almost 50 years. It is currently a pretty slow enzyme, [taking] carbon dioxide from the air and energy from the sun,” Lin said. “It produces an excess of carbon for the plant.”
According to the authors, Rubisco has co-evolved in plants for more than two and half billion years. This evolution has come as a result of the enzyme’s responsiveness to fluctuations of carbon dioxide and oxygen in the air and temperature.
As the plant faces changes to the atmosphere, the efficiency of the Rubisco enzyme also begins to change. In an environment with a decrease in carbon dioxide concentrations and an increase in oxygen, a chemical reaction called “photorespiration” occurs more frequently, which decreases the output of glucose made during photosynthesis.
Photorespiration is a less efficient production of energy because it uses more energy to produce less glucose, or food, for the plant to grow, than compared to photosynthesis. However, in an environment with high levels of carbon dioxide, low levels of oxygen and extreme heat, ancestral Rubisco was found to perform photosynthesis more efficiently.
“500 to 800 ppm was the carbon saturation in the air a long time ago, and it has decreased over time,” Lin said. “Rubisco has evolved in very low carbon dioxide conditions since then, and now we are trying to help the plants adapt to these new conditions in our climate where carbon dioxide is high and there are higher temperatures.”
The current average saturation of carbon in the atmosphere is around 420 ppm, and is expected to continue growing. However, the current evolved Rubisco in plants has not caught up with our quickly changing climate.
While there have been long-standing concerns over the genetic modification of plants, Lin explained that it is necessary to intervene in plant processes to increase the efficiency of photosynthesis because the yield of our farming crops depends on it.
“We have a pretty good mapping of the more common plant genomes that we will alter already, and a good understanding of the proteins that we are altering,” Lin said. “Right now we see no possible negatives, in pursuing this type of modification to crop plants.”
While performing their study, the Cornell team found that by combining a more efficient Rubisco enzyme with a plant already predisposed to take in more carbon dioxide, the rate of photosynthesis would increase by 25 percent.
“This will have a broad impact, for crops that aren’t already efficient,” Lin explained. “Rice, soybeans, and wheat will produce more benefits from the introduction of a more efficient Rubisco.”
In 2012, there was a global stagnation observed in the growth of our crop yields of maize, rice, wheat and soybeans. With an increasingly growing world population, the utilization of Rubisco could increase yields that will be paramount for future generations.
“All of the carbon in our body is produced from Rubisco. We get it from the plants that we consume, and the animals we eat get it from the plants that they consume,” Lin said. “This enzyme is very important for the future of agriculture.”
While this study explored the enzyme within a tobacco plant, the research team expects crop testing within the next ten to fifteen years.“After our current research in the Solanaceous plant — tobacco — we hope to put it into other plants, and then test it, which will take a few years,” Lin said. “After that we can test it on actual crops, which will take another three to four years. For a global impact of this research, we can expect an outcome in about five to ten years.”