CO2 Signal Transduction in Plants

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Stomata are the pores on the surface of leaves that 1) regulate the diffusion of carbon dioxide from the atmosphere into leaves for photosynthetic carbon fixation and 2) control the transpirational water loss of plants. Guard cells sense carbon dioxide concentration, water status, light and other environmental stimuli and integrate these to regulate stomatal apertures for optimization of carbon dioxide influx into plants, water loss and plant growth under diverse conditions. For example, elevated carbon dioxide concentrations in leaves cause stomatal closure, whereas reduced carbon dioxide concentrations result in stomatal opening. The concentration of atmospheric carbon dioxide is predicted to double within the present century: carbon dioxide at these increased levels is known to reduce the stomatal apertures of various plant species by up to 40%. This will have profound effects on global gas exchange between plants and the atmosphere and the efficiency of plant water use. However, relatively little is known about the molecular signal transduction mechanisms that mediate carbon dioxide-induced stomatal movements. Using the model plant Arabidopsis, the PI has shown that knock-out mutants in genes encoding carbonic anhydrase show an impaired carbon dioxide-induced stomatal movement response. The hypothesis that these proteins function in early carbon dioxide control of gas exchange regulation will be investigated. In this project, the genetic, molecular, cellular and physiological mechanisms by which these proteins mediate the stomatal response to carbon dioxide concentrations will be characterized.Broader Impacts: The P.I. will pursue outreach efforts through public forums and through research and career training and preparation of high school students and undergraduate students. Underrepresented minority students will be trained to pursue supervised independent research projects. In addition the P.I. is training and preparing post doctoral and graduate scientists for advanced independent careers in research, technology and science education. Understanding the molecular mechanisms by which carbon dioxide modulates stomatal conductance is fundamental to understanding the regulation of gas exchange between plants and the atmosphere, will help to predict effects of atmospheric carbon dioxide elevation on plants, and may also contribute to future engineering of water use efficiency or leaf heat stress avoidance in crop plants and plant carbon sinks in the face of the continuing atmospheric carbon dioxide rise and climate change.