Dellero Younès

Research scientist at INRAE Rennes, France

Contact address

UMR1349 IGEPP, INRAE – Agrocampus Ouest – Université Rennes1, Domaine de la Motte, BP 35327, 35653 Le Rheu Cedex, France

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Expertise

• Sink-source relationships
• Interactions between carbon and nitrogen metabolisms during abiotic stress

Skills

• Metabolomic and fluxomic approaches
• Plant physiology
• Biochemistry
• Functional genetics
• Engineering of metabolic pathway

Career

Since 2018: INRAE Scientist (CRCN) at INRAE Rennes (France). Team « Yield under Abiotic Challenges » (Head: N. Nesi).

2016-2018: Post-doctoral fellow at the Cell and Plant Physiology Laboratory (Grenoble, France). Team « Biogenesis, dynamics and homeostasis of membrane lipids » (Heads: E. Maréchal and J. Jouhet)

2012-2015: Ph.D. in Plant Sciences at the Institute of Paris-Saclay Plant Sciences (IPS2, Paris, France). Team « Signaling, regulation and metabolic interactions » (Head: M. Hodges)

2012: Master of Plant Sciences at the South Paris University, the AgroParisTech School and the National Superior School of Cachan (Paris, France)

2010: Bachelor in Molecular and Cellular Biology at the South Paris University (Paris, France)

Research interests 

My research project is part of the team entitled “ Yield under Abiotic Challenges ” and focuses on the regulation of leaf primary metabolism during development and abiotic stress. To gain knowledge on the functioning of major metabolic networks in photosynthetic tissues, I notably develop ¹³C and ¹⁵N-INST-MFA (Isotopically Non-STationary Metabolic Flux Analysis) fluxomic approaches in collaboration with the metabolomic platforms P2M2 (Rennes) and MetaToul-metabolic networks (Toulouse) and with the METASYS team from INSA-Toulouse, expert in metabolic flux modelling. I have a particular interest in understanding how the modifications of specific metabolic fluxes allow plants to adapt to developmental and abiotic stress.

I am working on the following topics:

1) Amino acid metabolism and mitochondrial respiration during senescence

Senescence is a major process tightly controlled by the hormonal balance that leads to nutrient remobilisation from source-to-sink organs of plants. Senescence can be induced by leaf ageing but also by a wide range of abiotic and biotic stresses. During the first stages of senescence, chloroplasts are extensively degraded by the autophagy machinery in source leaves, leading to the massive production of amino acids, while mitochondria remain operational until the last stages of senescence. Indeed, nutrient remobilisation processes require many energy, which may explain the need to maintain mitochondrial energy production in the absence of functional chloroplasts. Recent works showed that the catabolism of Isoleucine, Leucine, Lysine, Proline, Tyrosine and Valine can significantly contribute to mitochondrial respiration during dark-induced senescence in Arabidopsis. Using transcriptomic, metabolomic and fluxomic approaches, I investigate the importance of these pathways for nutrient remobilization during natural senescence in crops.

2) Flux modes in the plant TriCarboxylic Acid (TCA) cycle

TCA cycle is a major pathway of plant central carbon metabolism. It provides several essential functions for the development and growth of plants by: i) producing reduced NADH and succinate for mitochondrial energy production through the mitochondrial electron transfer chain; ii) producing carbon skeletons for nitrogen assimilation and amino acid biosynthesis (2-oxoglutarate and oxaloacetate notably); iii) recycling the fumarate produced during purine nucleotide biosynthesis. However, TCA cycle enzymes can have multiple subcellular localizations, which further increases the complexity of the interactions of the TCA cycle with other metabolic pathways. Depending on the organ considered and the environmental conditions, the conventional TCA cycle can adopt different flux modes and parts of the TCA cycle have to compete with alternative pathways such as the GABA shunt, the glyoxylate cycle or the PEPc-derived anaplerotic pathway. Using a ¹³C-INST-MFA fluxomic approach, I am interested in modelling the impact of sink/source relationships and abiotic stress on the topology of TCA cycle.

3) Cross regulations between photosynthesis, photorespiration, mitochondrial respiration and nitrogen assimilation during adaptation to drought stress

When plants perceive a drought stress, roots produce a phytohormone (abscissic acid) that is transported to guard cells of leaves to induce stomatal closure, which in turn decreases water losses by transpiration. However, stomatal closure has major consequences on leaf primary metabolism and plant fitness. First, it decreases the CO₂/O₂ ratio for RuBiSCO, which in turn decreases net carbon fixation and increases carbon and nitrogen lost by photorespiration. Second, it decreases the negative pressure/tension at the top of the plant and thereafter the xylem-dependent transport of water and nutrients from root-to-shoot. While plants can produce and accumulate compatible osmolytes (proline, betaines, sugars) to cope with long-term drought stress, the adaptation to short-term drought stress requires fine adjustments of leaf primary metabolism that still remain to be investigated. Indeed, major pathways of leaf primary metabolism (photosynthesis, photorespiration, glycolysis, TCA cycle, nitrogen assimilation) are strongly entangled together and are subject to numerous metabolic and redox feedback mechanisms. Using physiological and fluxomic approaches, I characterize the cross regulations between photosynthesis, photorespiration, mitochondrial respiration and nitrogen assimilation operating during adaptation to drought stress.

Projects

• 2018-2020: INRA Grant (30 k€): “Impact of the sink/source balance on the regulation of metabolic fluxes associated with amino acid metabolism in oilseed rape leaves” (PI: Y. Dellero)

Team «Yield under Abiotic Challenges » focus
/Research-teams/Yield-under-Abiotic-Challenges

Organizational Chart of the Team «Yield under Abiotic Challenges »
/Research-teams/Yield-under-Abiotic-Challenges/Staff

Related publications

Dellero Y. Manipulating amino acid metabolism to improve crop nitrogen use efficiency for sustainable agriculture. under review in J Exp Bot.

Dellero Y, Clouet V, Marnet N, Pellizzaro A, Dechaumet S, Niogret MF, Bouchereau A. 2020. Leaf status and environmental signals jointly regulate proline metabolism in winter oilseed rape. J Exp Bot 71, 2098-2111.

Dellero Y, Heuillet M, Marnet N, Bellvert F, Millard P, Bouchereau A. 2020. Sink/Source Balance of Leaves Influences Amino Acid Pools and Their Associated Metabolic Fluxes in Winter Oilseed Rape (Brassica napus L.). Metabolites 10.

Dellero Y, Jossier M, Glab N, Oury C, Tcherkez G, Hodges M. 2016. Decreased glycolate oxidase activity leads to altered carbon allocation and leaf senescence after a transfer from high CO2 to ambient air in Arabidopsis thaliana. J Exp Bot 67, 3149-3163.

Hodges M, Dellero Y, Keech O, Betti M, Raghavendra AS, Sage R, Zhu XG, Allen DK, Weber AP. 2016. Perspectives for a better understanding of the metabolic integration of photorespiration within a complex plant primary metabolism network. J Exp Bot 67, 3015-3026.

Dellero Y, Lamothe-Sibold M, Jossier M, Hodges M. 2015. Arabidopsis thaliana ggt1 photorespiratory mutants maintain leaf carbon/nitrogen balance by reducing RuBisCO content and plant growth. Plant J 83, 1005-1018.