The role of carbonic anhydrase in photosynthesis in Arabidopsis

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This project will investigate whether carbonic anhydrase (CA), an enzyme that catalyzes the interconversion of CO2 and HCO3-, facilitates CO2 fixation in plants that perform C3 photosynthesis. Moroney et al. (2001) Plant, Cell Environ. 24: 141 reported that Arabidopsis possesses at least 14 CA genes. Preliminary results showed that a double mutant missing two cytosolic CAs, βCA2 and βCA3, exhibited reduced growth and a reduced affinity for CO2 indicating these CAs play an integral role in CO2 fixation. The overall goal of this project is to determine the roles and importance of different CA enzymes for photosynthesis in C3 plants. The work will involve a molecular characterization of leaf CAs in Arabidopsis and a reverse genetics approach to obtain knockout Arabidopsis plants missing one or more CA isoforms. Using the knock-out plants, the physiological roles of the specific CA isoforms will be determined by measuring gas exchange, mesophyll conductance, and isotopic discrimination in whole plants. Recently, Zhu et al. (2010) Ann Rev. Plant Biol. 61: 235 pointed out that a significant limitation to CO2 fixation in C3 plants is the resistances to the diffusion of CO2 from outside mesophyll cells to chloroplasts. This research project will increase our understanding of the factors that affect CO2 fixation allowing scientists to better formulate strategies to improve CO2 delivery and crop yield particularly in the face of increasing atmospheric CO2. This project will be an important component in the education of graduate and undergraduate students. At LSU, there are many programs to foster participation of a diverse group of students in hands-on research, providing a framework for these students to go on to successful careers in industry, medicine and academics.