Doctoral candidate :  Henri Pégeot
University :  Université de Lorraine, France
Contract duration :  2012-2015

Research topic  — Structural and functional study of glutathione transferase (GST) of the Phi class in poplar tree Populus trichocarpa.

Research team and supervising scientists —
Research team: Stress response and redox regulation
PhD supervisor: Nicolas Rouhier
PhD co-supervisor: Arnaud Hecker

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Context and state of the art — Glutathione transferases are ubiquitous enzymes found in eukaryotes and prokaryotes. These proteins provide protection against toxic endogenous and xenobiotic molecules by catalyzing the conjugation of the tripeptide glutathione on these molecules. Populus trichocarpa contains at least 80 GST divided into nine classes. The Phi class is nearly always specific to plants and regroups eight isoforms displaying strong identity while suggesting functional redundancy. These are enzymes approximately 25 kDa in size with a catalytic serine. Proteomic and transcriptomic studies have shown that these genes are induced in response to numerous stress conditions. However, the precise physiological function and the substrates of these GST remain unknown.

Aims and specific questions to be addressed —  The project aims to provide structure-function analysis of Phi glutathione transferases (GST) from poplar trees (Populus trichocarpa) to identify their physiological roles and characteristics of each isoform.

Science and innovation issues  — Poplar is a common species in Europe and is vital for the proper functioning of numerous biotopes. On the other hand, poplars are largely cultivated in forestry and horticulture, given their rapid growth properties. These trees are subject to numerous environmental constraints such as pathogen attacks or other stresses resulting from climatic changes. Several research centers are currently working on biotechnological processes aimed to genetically improve the poplar species and to create new varieties more tolerant to those stresses and useable in phytoremediation. From a purely fundamental standpoint, understanding these stress response mechanisms induced by such constraints is a crucial first step before considering ways to fight against these stresses.

Methodological approaches and expected results  — The characterization of Phi GST will be divided into three main axes combining multidisciplinary approaches:

(i)  Study of enzymatic and structural properties
(ii)  Study of the amount of transcripts and proteins in poplar tissues
(iii)  Identification of physiological substrates (proteins, metabolites, xenobiotics)

Considering the scope of the project and the expected results, we expect to be able to publish several research articles in plant biology, biochemistry and structural biology journals.