Scientists working to build a better leaf

Researchers have been trying for decades to improve upon Mother Nature's favorite solar-power trick — photosynthesis — but now they finally think they see the sunlight at the end of the tunnel.

"We now understand photosynthesis much better than we did 20 years ago," said Richard Cogdell, a botanist at the University of Glasgow who has been doing research on bacterial photosynthesis for more than 30 years. He and three colleagues discussed their efforts to tweak the process that powers the world's plant life today in Vancouver, Canada, during the annual meeting of the American Association for the Advancement of Science.

The researchers are taking different approaches to the challenge, but what they have in common is their search for ways to get something extra out of the biochemical process that uses sunlight to turn carbon dioxide and water into sugar and oxygen. "You can really view photosynthesis as an assembly line with about 168 steps," said Steve Long, head of the University of Illinois' Photosynthesis and Atmospheric Change Laboratory.

Revving up Rubisco
Howard Griffiths, a plant physiologist at the University of Cambridge, just wants to make improvements in one section of that assembly line. His research focuses on ways to get more power out of the part of the process driven by an enzyme called Rubisco. He said he's trying to do what many auto mechanics have done to make their engines run more efficiently: "You turbocharge it."

Some plants, such as sugar cane and corn, already have a turbocharged Rubisco engine, thanks to amolecular pathway known as C4. Geneticists believe the C4 pathway started playing a significant role in plant physiology in just the past 10 million years or so. Now Griffiths is looking into strategies to add the C4 turbocharger to rice, which ranks among the world's most widely planted staple crops.

The new cellular machinery might be packaged in a micro-compartment that operates within the plant cell. That's the way biochemical turbochargers work in algae and cyanobacteria. Griffiths and his colleagues are looking at ways to create similar micro-compartments for higher plants. The payoff would come in the form of more efficient carbon dioxide conversion, with higher crop productivity as a result. "For a given amount of carbon gain, the plant uses less water," Griffiths said.

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