Newly identified enzymes help plants sense elevated CO2 and could lead to water-wise crops

Biologists have identified plant enzymes that may help to engineerplants that take advantage of elevated carbon dioxide to use water moreefficiently. The finding could help to engineer crops that takeadvantage of rising greenhouse gases.

Plants take in the carbon dioxide they need for photosynthesisthrough microscopic breathing pores in the surface of leaves. But foreach molecule of the gas gained, they lose hundreds of water moleculesthrough these same openings. The pores can tighten to save water whenCO2 is abundant, but scientists didn't know how that worked until now.

A team led by Julian Schroeder, professor of biology at theUniversity of California, San Diego, has identified the protein sensorsthat control the response. Enzymes that react with CO2 cause cellssurrounding the opening of the pores to close down they report in thejournal Nature Cell Biology online December 13.

The discovery could help to boost the response in plants that do nottake full advantage of elevated levels of the gas, Schroeder says. 'Alot of plants have a very weak response to CO2. So even thoughatmospheric CO2 is much higher than it was before the industrial ageand is continuing to increase, there are plants that are notcapitalizing on that. They're not narrowing their pores, which wouldallow them to take in CO2, while losing less water,' he said. 'It couldbe that with these enzymes, you can improve how efficiently plants usewater, while taking in CO2 for photosynthesis. Our data in the labsuggest that the CO2 response can be cranked up.'

Plants lose 95 percent of the water they take in to evaporationthrough these pores, also called stoma. Modifying crops to be moreresponsive to CO2 could help farmers meet demand for food ascompetition for water increases. In California, for example, 79 percentof water diverted from streams and rivers or pumped from the ground isused for agriculture according to the California Department of WaterResources.