Séminaire de Younès Dellero

“Using 13 C metabolic probes to assess carbon allocation processes within central metabolism of Brassica napus”

Plant central metabolism comprises several essential metabolic pathways acting together to support plant growth and yield establishment. The deployment of 13 C- tracing dynamic approaches in the model Brassicaceae species Arabidopsis allowed to improve our understanding of this complex metabolic network by identifying major leaf carbon allocation processes. However, some questions remained open for Brassica napus leaves, an economically relevant oleaginous crop experiencing sequential senescence during its vegetative growth. Notably, the functioning of the tricarboxylic acid (TCA) cycle in the light in relation to glycolysis, Calvin cycle, photorespiration and branched-chain amino acid catabolism could be substantially different in source leaves in order to support senescence-associated remobilization processes. Here, we investigated these carbon fluxes by performing short-term incorporations of different fully 13 C-labelled metabolic probes into Brassica napus leaf discs. Indeed, this experimental setup showed relatively similar photosynthetic and respiratory capacities compared to attached leaves. Evaluation of 13 C-enrichments at
molecular and isotopologue levels by GC-MS identified light/dark regulation of key carbon fluxes and separated competing metabolic contributions to metabolite biosynthesis. Notably, the results supported: i) the occurrence of both cyclic and non-cyclic flux modes of TCA cycle in the light; ii) the contribution of glycolysis rather than stored citrate to TCA cycle functioning in the light; iii) the reallocation of TCA cycle decarboxylations back to the TCA cycle through photorespiration and glycolysis; iv) The multiple contributions of branched-chain amino acid catabolism to TCA cycle in the light. Overall, our results improved our understanding of central metabolism in source leaves of Brassica napus.

Younès Dellero 1,2,3 , Mathieu Aubert 1 , Solenne Berardocco 1,2,3 , Olivier
Filangi 1,2,3 , Alain Bouchereau 1,2,3 ,
Affiliations
1 INRAE, Université de Rennes, Institut Agro, IGEPP-UMR1349, Le Rheu, 35653,
France
2 Metabolic Profiling and Metabolomics Platform – P2M2, IGEPP-UMR1349, Le Rheu,
35653, France
3 MetaboHUB-Grand-Ouest (Rennes), France