PARENT SESSION

Symposium S3C C3 and Rubisco
Tuesday August 31st, 2004 10:20 AM-12:20 PM Room 510A
Chair: Michael Salvucci
Co-Chair: Akiho Yokota

Does the current C2 cycle scheme need a major revision? Hermann Bauwe^*,, Uener Kolukisaoglu, Ralf Boldt, Kirsten van den Daele, Christoph Edner, Nadja Engel, Thomas Hartwig, Nanette Sievers¹, ¹ Rostock University, Plant Physiology Department, Rostock, Germany

ABSTRACT- The C2 cycle, by making autotrophic CO2 fixation possible in an atmosphere containing high oxygen concentrations, is an indispensable pathway for the life at least of higher plants. In course of the respective enzymatic reactions, a significant part of the freshly assimilated carbon is sacrificed to survive in an otherwise toxic environment (Osmond, 1981). The biochemistry and cellular biology of the metabolic processes that make up the C2 cycle is very complex and quite well but, despite long-term research efforts, not yet fully understood. The core of the C2 cycle involves at least nine individual enzymatic reactions localized in three different organelles. Most of these enzymes are encoded by gene families but some by single genes. We are analyzing the function and interaction of the respective genes by making use of T-DNA insertional mutants of Arabidopsis thaliana. In addition, we are mapping the mutations in several of the Arabidopsis mutants produced earlier in the Ogren group by chemical mutagenesis with subsequent high CO2 screenings (Somerville, 2001). The metabolic analysis of genetically defined C2 cycle insertional mutants in combination with the re-analysis of the above-mentioned older mutants in our group suggests that current textbook schemes of the C2 cycle probably need to be revised with respect to several of the individual enzymatic steps and with respect to the integration of new essential components. (Osmond CB. 1981. Photorespiration and photoinhibition. Some implications for the energetics of photosynthesis. Biochimica et Biophysica Acta 639, 77-98. Somerville CR. 2001. An early Arabidopsis demonstration resolving a few issues concerning photorespiration. Plant Physiology 125, 20-24.)

KEY WORDS: c2 cycle, photorespiration, glycolate metabolism