Screening for high CO2 responsive mutants of Arabidopsis

Abstract

As atmospheric levels of CO2 continue to rise, there is significant interest in the mechanisms by which plants can respond to these changes. To identify specific genes involved in high CO2 acclimation, we have been screening for Arabidopsis mutants that exhibit a non-wild type response when exposed to elevated (1000 ppm) CO2 concentrations. Two classes of mutants have been characterized. The first, designated as CO2 non-responsive (cnr), do not display the typical stress responses of increased anthocyanin production, leaf cupping, and stunted growth found in wild type plants exposed to similar high CO2 levels. The second group of mutants are described as CO2 hyper-responsive (chr) in that their stress responses are more severe than wild type plants. Characterization of these mutants has involved an analysis of growth and morphology, photosynthetic capacity, foliar carbohydrate levels, and photosynthetic gene (ca1, cab, rbcS) transcript abundance. The relationship between the high CO2 phenotypes and growth in the presence of high levels of glucose/sucrose will also be described. Molecular characterization of two cnr mutants isolated from T-DNA tagged populations has identified two different mechanisms by which Arabidopsis is able to minimize a stress response to high level of CO2.