JCJC SVSE 6 - JCJC - SVSE 6 - Génomique, génétique, bioinformatique et biologie systémique

Leaf respiration: from flux-modes to C1 metabolism. – FMC

Is respiration at the heart of plant growth ?

The aim of the project is to elucidate the relationships between leaf metabolic pathways, including interactions between respiration and nutrient assimilation (nitrogen, sulfur).

How does leaf metabolism reconcile contrasted imperatives ?

Plant leaves are the major site of carbon fixation by photosynthesis. However, photosynthesis is not the sole metabolic process operating in the light since photorespiration, respiration and nutrient (N, S) assimilation also occur. There are interactions between these phenomena with common molecules participating to the different metabolic pathways. For example, the exchange of one-carbon units (methyl, methylene, formyl), so called “C1 metabolism” is involved in both photorespiration and amino acid synthesis. Presently, the means by which leaf metabolism reconciles the whole picture and reach homeostasis (adjustment to physiological levels) are unknown. Elucidating these aspects is the very aim of the project.

The key aspect of techniques is to exploit methods providing information in vivo, with intact leaves and not reconstituted cellular systems – which generally have different metabolic properties. The project takes advantage of (i) particular gas exchange systems allowing instant sampling with liquid nitrogen, (ii) isotopic tracing, (iii) omics methods providing the whole picture for metabolites or proteins and (iv) specific NMR analyses (e.g. 33S).

To be completed when available.

To be completed when available.

To be completed when available.

Elucidating the impact of respiration on plant and crop carbon balance is a persisting conundrum of physiology since respiration is both detrimental to plant biomass production (carbon loss in the form of CO2) and beneficial for nutrient assimilation (such as nitrogen) and growth. Furthermore, leaf respiration is at the heart of interactions between photosynthesis, photorespiration and mitochondrial metabolism and therefore, it is believed to be orchestrated by a complex regulation network, that may in turn be influenced by environmental changes (e.g. light/dark transition, atmospheric CO2 and temperature). Still, there are presently many enduring uncertainties about respiratory function in photosynthetic organs. So is the case of (i) possible robust relationships between ecophysiological leaf traits and respiration rate, (ii) fundamental fluxes that describe respiratory gas exchange, (iii) metabolic flux patterns associated with respiration and (iv) the effect of respiration on carbon and isotopic balance. In the present project, we intend to use post-genomic approaches (mainly, proteomics, fluxomics and isotopic facilities) to better understand metabolic commitments as well as respiratory responses to environmental conditions, from the cellular to the organ level. We propose to develop mostly in vivo and analytical methods to characterize leaf respiration, identify key regulators and appreciate the impact of respiration on other metabolisms like C1-metabolism. This project takes advantage of our expertise in isotopic methods adapted for plant biology. The ‘generalized fluxomic’ approach proposed in the project (i.e. carrying out extensive flux pattern studies) should provide a neat advance in understanding the metabolic orchestration of plant respiration.

Project coordinator

Monsieur Guillaume TCHERKEZ (Universite Paris-Sud/Institut de Biologie des Plantes) – guillaume.tcherkez@u-psud.fr

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

UPS/IBP Universite Paris-Sud/Institut de Biologie des Plantes

Help of the ANR 214,968 euros
Beginning and duration of the scientific project: January 2013 - 36 Months

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