Robust Plants' Secret? Rubisco
Activase! By Marcia Wood
November 22, 2002
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.