Scientists have long-sought to optimize photosynthesis to improve agricultural efficiency. Specifically, research has focused on modifying the key rate-limiting enzyme in carbon fixation, RuBisCo. A team of researchers at the Cornell-affiliated Boyce Thompson Institute have found a way to “turbocharge” photosynthesis by manipulating corn plants to overproduce the enzyme. The results show that this procedure can significantly boost corn crop performance, and may be a game-changer in crop genetic engineering.
According to Coralie Salesse-Smith, a doctoral candidate in plant biology, RuBisCo is one of the most abundant proteins on Earth. Its role is to catalyze an important step of plant photosynthesis, taking carbon dioxide from the atmosphere and converting it to sugars for plant growth.
Salesse-Smith calls RuBisCo an “inefficient protein” since the enzyme evolved at a time when oxygen levels were much lower, and cannot differentiate between carbon dioxide and oxygen. This causes it to sometimes waste energy by fixing oxygen.
While much research has been dedicated to improving RuBisCo’s properties by gene editing, the scientists at BTI took a different approach. “We actually haven’t added anything to corn plants that weren’t already in there. We’re just giving them more doses, if you will, of what they already do,” said Prof. David Stern, plant biology, and president of BTI.
“The other approach is just to make more of this enzyme; as slow as it is, if you make more, it’s like adding lanes to a clogged freeway,” Stern explained. “Maybe the cars can go a little faster.”
Compared to other plants, like soybeans and wheat, corn plants need much less nitrogen and energy to build RuBisCo, which is adapted to drier environments. Stern said that the thought process was that in corn you could potentially teach the plant to make more RuBisCo without causing problems related to nitrogen limitation.
That insight proved to be correct.
“Increasing expression of the large and small subunits that make up RuBisCo, as well as a chaperone protein, RuBisCo Assembly Factor 1, which helps assemble the subunits, caused the corn plants to produce more of the RuBisCo enzyme,” Salesse-Smith said.
The results, recently published in an article in Nature, found that increasing RuBisCo abundance caused plants in greenhouse conditions to grow taller, mature faster, and produce 15 percent more biomass.
With more maize grown annually than rice or wheat, these findings could greatly improve agricultural yield and efficiency if applied in the field. According to Stern, a company has already licensed the technique.
“The long-term societal goal is to make farming more efficient, so its footprint is reduced,” said Stern, “but Boyce Thompson is for discoveries. So we put out these discoveries and hope that people, like this company that we’ve partnered with, can make it work in the real world.”
According to Stern, BTI’s future study will focus on determining the underlying mechanism in order to further optimize photosynthesis.
“How does the plant translate this increase in ability to absorb carbon dioxide into a bigger plant? Carbon dioxide doesn’t, by itself, make the plant bigger,” Stern said. “Somehow the plant is taking advantage of this ability that we’ve given it, to grow faster. We want to find out how that’s happening.”
The group also plans to apply the same technique to other plants similar to corn, such as miscanthus, a biomass grass, and energy cane, an alternative source of ethanol.