Alain Bouchereau

Company
Department of Plant Genetics and Biotechnologies

Address
INRA-Agrocampus Rennes
Université de Rennes
BP 35327, 35653 Le Rheu Cedex

Telephone
+33223236997

E-mail
alain.bouchereau@univ-rennes1.fr

 

1. Summary of work to be allocated into a specific WG

We are involved for a long time in the characterization of the physiological and metabolic processes associated with the accumulation of compatible solutes in halophytic higher plants and glycophytic crops challenging drought and salt stresses. We also extend our approach in seeking their physiological properties and their usefullness when acting as inducible and mobile osmoregulators in vivo, giving a special attention to proline, betaines and cyclitols. These osmolytes and their related metabolic pathways are evaluated in terms of costs and benefits for plant cells under stress, while the relevance of the criterions used to assess the compatibility of the accumulated end-products is a strong matter of investigation. The changes in proline metabolism responsible for the accumulation of this amino acid are thoroughly studied, assuming that it could depend on the balance of increased de novo biosynthesis and decreased consumption via oxidative processes and in relation with protein recycling, redox buffering, nitrogen storage and metabolic homeostasis between subcellular compartments. This proline syndrome is associated with relevant changes in gene expression and enzyme activities on both synthesis and catabolism and is also shown to result from changes in the activity of the transport systems integrating its distribution both at the cell and the whole plant levels. Among regulating effects operating on the proline system, evidences are brought about the signaling involvement of phytohormones and plant growth regulators like abscisic acid, oxylipines and poly-insaturated fatty acids (jasmonate and derivatives) and polyamines. The work is mostly integrated into WG3.

Special emphasis are also directed to polyamine metabolism considered as primary actors of homeostatic adjustment in plants under environmental stress. Amines occurring under multiple chemical forms are recognized as both regulators of the abiotic stress response including accumulation of osmoprotective substances but also as effective intermediates involved in nitrogen metabolism adjustments and oxidative stress management. The contribution of stress-induced oxidative degradative pathways from aliphatic polyamines (i.e. putrescine, spermidine and spermine) catalysed by amine oxidases to the production of signaling actors of the stress response like g-aminobutyrate and b-alanine is under focus. . The work is mostly integrated into WG4.

2. Links with other WG and/or Subgroups

Our specific work is also linked with WG1.6, WG1.7, WG2.1, WG2.6. in order to study interactions with other signaling/metabolic pathways.

3. Specific activities to be integrated into WG and/or Subgroubs 

WG 3 : Expression of genes in glutamate-derived amino acids, chaperonines, proline and those of the aspartate family by hyperosmolarity, sugar and ABA.

We will focus on proline metabolism regulation in relation to the osmo-induced proteolysis and amino acids recycling. That will be achieved in Brassica and related species (Arabidopsis and Thellungiella) where a number of osmoregulated metabolic processes have already been described in relation to glutamate homeostasis achievement. Metabolic fluxes allowing carbon and nitrogen allocation from glutamate (deriving from proteolysis) to different related and putativeley competitive routes (proline production, glutamine production, g-amino-butyrate synthesis, lysine degradation, pipecolic acid synthesis) will be investigated assuming different costs and benefits for cellular homeostasis, osmoregulation, chemical chaperoning, redox buffering, stress signaling, nitrogen storage, potentialisation of pentose phosphate pathway and secondary metabolism, mitochondrial functionning.

Special attention will be attributed to the contribution of proline degradation and proline dehydrogenases activities in the regulation of proline pools under water stress and after stress recovering. That will be achieved in collaboration with partners involved in WG 1 and WG 2.

WG 4 : Integrated functional genomic and systems biology analysis of regulatory functions and transcrption regulation of all genes involved in polyamine metabolism, to render specific functions to the regulation of drought, salt and cold tolerance in Arabidopsis and other plant species.

We will mainly focus on polyamine oxidation and conjugation pathways and their contribution to the regulation of polyamine titers under stress conditions. Diamine and polyamine oxidases will be under focus. Polyamine metabolites and conjugates will be assessed as potential actors of the polyamine network operating during the osmotic and salt stress responses.

Plant systems under study are halophytic species of Plumbaginaceae (Limonium sp) and Brassicaceae (Thellungiella halophila) and crop species of Brassicaceae (Brassica napus) and Solanaceae (Lycopersicon esculentum). Arabidopsis thaliana (wild ecotypes, transgenics, mutants) genotypes are also used for genetic and genomic purposes.

4. Qualification for the role and current grants

The research group has 30 years of experience in the field of osmolyte production and compatible solutes accumulation and typology in higher plants (pioneered works of Profs. Goas and Larher). A number of metabolic adjustments have already been described in response to salt and water stress in halophytic and glycophytic species in relation to betaine (glycine betaine, b-alanine betaine, proline betaine) production, amino acids (proline, pipecolic acid, D-acetyl ornithine, g-aminobutyrate) accumulation and sugar and polyols metabolism.

We have also a long experience in investigating the role of polyamines and polyamine metabolism in stress response of higher plants (pioneered works of Profs. Larher and Martin-Tanguy). Review articles have already been published on this topic

Two PhD thesis are currently perfomed on these topics.

5. Technical expertise and facilities

We will provide all the technical skills required for stress metabolism investigations dealing with compatible solutes accumulation (proline, betaine, polyols) and amine profiling. Multiple transgenic and mutant lines of Arabidopsis affected for osmolyte production are already available. We are also a member of the Thellungiella consortium which aims at developping studies on this extremophile Arabidopsis related species as a reliable plant model for abiotic stress tolerance investigations (http://www.thellungiella.org/).

Canola and Tomato genotypes are also under investigations for agronomical perspectives.

Since a few years, the group invests with the development of reliable and efficient methodological tools for metabolic phenotyping and metabolomics of plants under abiotic stress environments.

Technical skills and methodological approaches are mainly relevant to whole plant physiology (water status, gas exchange, sink-sources relationships), tissue and cell biology (sub-cellular compartmentation, cell cultures, pharmacological studies), molecular biology (transcript profiling, northern-blotting, cloning, sequencing, transformation), protein biochemistry (production of heterologous proteins, enzymology, western-blotting), targetted metabolite profiling (HPLC, GC, MS, NMR, radio-labelling, stable isotopes) and metabolomics.