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Metabolic carbon fluxes and isotope effects in plants: photosynthetic CO2 fixation and day respiration, Guillaume Tcherkez


Plant metabolism is associated with 12C/13C isotope fractionation causing substantial isotopic differences between metabolites and also between source carbon and end products such as evolved CO2. Here, we will focus on two metabolic examples, CO2 fixation by Rubisco and CO2 production by leaf respiration in the light.

The origin of the 12C/13C isotope effect associated with Rubisco catalysis will be examined and the relationships with the chemical mechanism will be explored, by manipulating rates of elemental steps with H/D isotope effects (solvent isotope effects).

CO2 evolution by day respiration is a rather complex phenomenon since it is influenced by other metabolisms such as N assimilation and photorespiration. The combination of isotope-assisted metabolomics (labelling) and natural 13C abundance measurements show that CO2 evolved in the light comes from a slow turn-overed carbon pool, and is naturally 13C-depleted, likely due to enzymatic isotope effects in, e.g., decarboxylases.

Lunch will be provided.

Location: Eno Hall, Room 209

Date/Time: 06/16/14 at 12:30 pm - 06/16/14 at 2:00 pm

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Guillaume Tcherkez did his PhD at Uni Paris-Sud on plant functional ecology, using stable carbon isotopes. After a post-doc at the Australian National University (with G. Farquhar), he was appointed as a lecturer and then head professor at Uni Paris-Sud and since then, is in charge of the metabolomics and isotopics facility Platform Metabolism-Metabolome (www.pmm.u-psud.fr). His major discoveries are: the chemical compromise at the origin of the ‘Rubisco paradox’, the metabolism of day respiration in illuminated leaves, and the origin of isotopic patterns (including intramolecular 13C-patterns in sugars). In 2008, he was awarded the bronze medal of the CNRS (French National Center for Scientific Research). In 2015, he will join the Australian National University as full professor at the Research School of Biology.

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Department: Princeton Environmental Institute (PEI)