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SémIDEEV à l’UMR Génétique Quantitative et Évolution – Le Moulon


Ferme du Moulon – Salle de conférences

Mardi  26  mars  2019


Guillaume TCHERKEZ
Research School of Biology, ANU Joint College of Sciences,
Australian National University, Canberra, ACT, Australia

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"Unexpected metabolic effects of photorespiratory conditions in C3 plants

revealed by isotopic techniques"


The cornerstone of plant growth and crop production is photosynthesis, which involves CO2 incorporation via Rubisco-catalyzed carboxylation. Net photosynthesis is a complex process that encapsulates not only carboxylation but also CO2 release by photorespiration and day respiration. Unsurprisingly, in the past few years, intense efforts have been devoted to eliminate photorespiration in order to increase CO2 capture by photosynthetic organs. However, despite several decades of research on leaf primary metabolism in the light and in the dark, metabolic processes that accompany photorespiration when gaseous conditions vary (CO2/O2) are not well documented.

We recently showed that at high photorespiration, non-quantitativity of the photorespiratory Gly-to-Ser conversion leads to an increased demand in N assimilation and perturbs glutamate and glutamine metabolism. However, it remains uncertain whether this is accompanied by a concurrent increase in PEPC-fixation (which usually correlates to nitrate assimilation) and/or changes in sulphate assimilation (which requires reduction and assimilation onto organic molecules, like nitrate). An obvious technical difficulty to assess these phenomena is the rather low flux associated with PEPC and sulphur assimilation, and the need to measure fluxes in vivo. Using isotopic, high-resolution techniques, we demonstrate that both sulphur assimilation and PEPC activity are stimulated by photorespiratory conditions. This metabolic interaction between photorespiration and minor but critically important pathways contributes to explaining why it might not be so desirable to eliminate photorespiration by metabolic engineering.