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Robust Plants' Secret? Rubisco Activase!

Green plants must have a hardworking enzyme--called rubisco--in their leaves in order to grow. Ongoing investigations by Agricultural Research Service scientists in Phoenix, Ariz., have uncovered secrets about the pivotal role of a companion enzyme, rubisco activase.

Rubisco activase helps convert rubisco from an inactive to an active form. That's essential. Only active rubisco can help plants convert sunlight, water from the soil, and carbon dioxide from the air into food that they need for growth.

This process--called photosynthesis--slows if leaf cells have more inactive than active rubisco. The result? Plants don't grow as fast, and harvests aren't as bountiful, according to plant physiologist Steven J. Crafts-Brandner of the ARS Western Cotton Research Laboratory in Phoenix. He did the rubisco activase studies with Michael E. Salvucci, also a plant physiologist at the laboratory.

A plant could end up with more inactive than active rubisco if rubisco activase is inhibited by high temperatures or high carbon dioxide, the scientists found. No one had previously identified rubisco activase as the culprit that limits photosynthesis under these climatic conditions.

Damage-causing high temperatures can occur in the arid Southwest as well as in the South and Southeast. And, worldwide records of the past 100 years indicate a gradual warming trend and an increase in atmospheric carbon dioxide. Some experts predict both trends will continue.

The research should not only boost the accuracy of projections about how global climate change might affect green plants but should also lead to new strategies to help crop plants sidestep the unwanted, climate-driven influences on rubisco activase. For instance, Crafts-Brandner and Salvucci hope to find or construct genes that could cue plants to synthesize a more heat-stable rubisco activase. They're collaborating with Pioneer Hi-Bred International, Inc., of Des Moines, Iowa., in the research.

An article in the current issue of Agricultural Research magazine tells more.

ARS is the U.S. Department of Agriculture's chief scientific research agency.