Using high-performance computing and genetic engineering to boost the photosynthetic efficiency of plants offers the best hope of increasing crop yields enough to feed a planet expected to have 9.5 billion people on it by 2050, researchers report in the journal Cell.
There has never been a better time to try this, said University of Illinois plant biology professor Stephen P. Long, who wrote the report with colleagues from Illinois and the CAS-MPG Partner Institute of Computational Biology in Shanghai.
"We now know every step in the processes that drive photosynthesis in C3 crop plants such as soybeans and C4 plants such as maize," Long said. "We have unprecedented computational resources that allow us to model every stage of photosynthesis and determine where the bottlenecks are, and advances in genetic engineering will help us augment or circumvent those steps that impede efficiency."
Substantial progress has already been made in the lab and in computer models of photosynthesis, Long said.
"Our lab and others have put a gene from cyanobacteria into crop plants and found that it boosts the photosynthetic rate by 30 percent," he said.
Photosynthetic microbes offer other clues to improving photosynthesis in plants, the researchers report. For example, some bacteria and algae contain pigments that utilize more of the solar spectrum than plant pigments do. If added to plants, those pigments could bolster the plants' access to solar energy.
Some scientists are trying to engineer C4 photosynthesis in C3 plants, but this means altering plant anatomy, changing the expression of many genes and inserting new genes from C4 plants, Long said.
"Another, possibly simpler approach is to add to the C3 chloroplast the system used by blue-green algae," he said. This would increase the activity of Rubisco, an enzyme that catalyzes a vital step of the conversion of atmospheric carbon dioxide into plant biomass. Computer models suggest adding this system would increase photosynthesis as much as 60 percent, Long said.
Computer analyses of the way plant leaves intercept sunlight have revealed other ways to improve photosynthesis. Many plants intercept too much light in their topmost leaves and too little in lower leaves; this probably allows them to outcompete their neighbors, but in a farmer's field such competition is counterproductive, Long said.
Studies headed by U. of I. plant biology professor Donald Ort aim to make plants' upper leaves lighter, allowing more sunlight to penetrate to the light-starved lower leaves. Computer modeling of photosynthesis also shows researchers where the traffic jams occur -- the steps that slow the process down and reduce efficiency.
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