{"id":10614,"date":"2020-11-24T10:47:48","date_gmt":"2020-11-24T10:47:48","guid":{"rendered":"https:\/\/mycor.iam.inrae.fr\/IAM\/?p=10614"},"modified":"2020-11-24T12:06:08","modified_gmt":"2020-11-24T12:06:08","slug":"phd-defense-elodie-sylvestre-gonon","status":"publish","type":"post","link":"https:\/\/mycor.iam.inrae.fr\/IAM\/?p=10614","title":{"rendered":"PhD Defense: Elodie Sylvestre-Gonon"},"content":{"rendered":"

Elodie Sylvestre-Gonon soutiendra sa th\u00e8se, intitul\u00e9e \u00ab Caract\u00e9risation biochimique et structurale de quelques glutathion transf\u00e9rases de la classe Tau d’arabette (Arabidopsis thaliana<\/em>) et de peuplier (Populus trichocarpa<\/em>) \u00bb, le mardi 1er d\u00e9cembre 2020 \u00e0 14h en visioconf\u00e9rence sur TEAMS<\/a>.<\/p>\n

Ce travail de th\u00e8se a \u00e9t\u00e9 r\u00e9alis\u00e9 au sein de l\u2019UMR IAM sous la direction de Nicolas Rouhier et Arnaud Hecker.<\/p>\n

R\u00e9sum\u00e9 : <\/strong><\/p>\n

Les glutathion transf\u00e9rases (GSTs) constituent une famille multig\u00e9nique d\u2019enzymes ubiquitaires impliqu\u00e9es notamment dans la d\u00e9toxication des x\u00e9nobiotiques et le m\u00e9tabolisme secondaire. Les GSTs canoniques sont constitu\u00e9es d\u2019un domaine N-terminal de type thior\u00e9doxine et d\u2019un domaine C-terminal form\u00e9 d\u2019h\u00e9lices \u03b1. Chez les plantes terrestres, les GSTs peuvent \u00eatre regroup\u00e9es en 14 classes et selon le r\u00e9sidu conserv\u00e9 au sein de leur motif catalytique en GSTs \u00e0 cyst\u00e9ine (Cys-GSTs) ou \u00e0 s\u00e9rine (Ser-GSTs). Les Ser-GSTs pr\u00e9sentent des activit\u00e9s de r\u00e9duction des peroxydes et\/ou de conjugaison de glutathion (GSH) alors que les Cys-GSTs portent des activit\u00e9s de d\u00e9glutathionylation et d\u00e9shydroascorbate r\u00e9ductase. Certaines d\u2019entre elles pr\u00e9sentent \u00e9galement des propri\u00e9t\u00e9s non-catalytiques de type ligandine \u00e0 des fins de transport ou de stockage de mol\u00e9cules diverses. Les GSTs Tau (GSTUs) correspondent \u00e0 la classe regroupant le plus d\u2019isoformes chez les plantes et leur sont sp\u00e9cifiques. Les GSTUs sont souvent surexprim\u00e9es lors de stress biotiques et abiotiques et participent notamment \u00e0 la d\u00e9toxication des herbicides. Toutefois, le r\u00f4le physiologique des GSTUs reste encore lacunaire in planta. En combinant des approches phylog\u00e9n\u00e9tiques, biochimiques et structurales, ces travaux ont conduit \u00e0 la caract\u00e9risation de neuf GSTUs d\u2019Arabidopsis thaliana<\/em> (AtGSTUs) et de six GSTUs de Populus trichocarpa<\/em> (PtGSTUs). L\u2019analyse phylog\u00e9n\u00e9tique des Ser-GSTs d\u2019organismes photosynth\u00e9tiques a r\u00e9v\u00e9l\u00e9 que l\u2019expansion des GSTUs est apparue de fa\u00e7on concomitante \u00e0 l\u2019apparition du r\u00e9seau vasculaire chez les plantes bien que quelques mousses et bryophytes poss\u00e8dent des GSTUs. Au sein d\u2019un organisme, les GSTUs peuvent \u00eatre class\u00e9es en groupes distincts en fonction de leur motif catalytique. Les essais enzymatiques r\u00e9alis\u00e9s ont montr\u00e9 que quasiment toutes les GSTUs d\u2019int\u00e9r\u00eat portent des activit\u00e9s de conjugaison du GSH et de r\u00e9duction des peroxydes envers diff\u00e9rents substrats mod\u00e8les (CDNB, d\u00e9riv\u00e9s d\u2019isothiocyanates, hydroperoxydes). Les structures tridimensionnelles de deux GSTUs ont \u00e9t\u00e9 r\u00e9solues et ces derni\u00e8res pr\u00e9sentent le repliement classique des GSTs canoniques avec des diff\u00e9rences notables entre elles. Les analyses biochimiques et structurales r\u00e9alis\u00e9es sur les prot\u00e9ines AtGSTUs et PtGSTUs d\u2019int\u00e9r\u00eat ont montr\u00e9 que certaines d\u2019entre elles lient des porphyrines bact\u00e9riennes et d\u2019autres des compos\u00e9s polyph\u00e9noliques. Parmi les complexes enzyme-ligand identifi\u00e9s, la structure d\u2019un complexe baical\u00e9ine-GSTU a \u00e9t\u00e9 r\u00e9solue. L\u2019utilisation d\u2019\u00e9chantillons enrichis en m\u00e9tabolites extraits de plantes repr\u00e9sente la prochaine \u00e9tape sur le chemin de l\u2019analyse fonctionnelle des GSTUs.<\/p>\n

Abstract:<\/strong><\/p>\n

Biochemical and structural characterization of some glutathione transferases of the Tau class of Arabidopsis thaliana<\/em> and Populus trichocarpa<\/em>.<\/p>\n

Glutathione transferases (GSTs) constitute a ubiquitous multigene superfamily of enzymes involved in xenobiotic detoxification and secondary metabolism. Canonical GSTs consist of an N-terminal thioredoxin domain and a \u03b1-helical C-terminal domain. In terrestrial plants, GSTs can be grouped in 14 classes but also according to the conserved residue found in their catalytic site either cysteine (Cys-GSTs) or serine (Ser-GSTs) GSTs. Ser-GSTs exhibit reduction of peroxides and\/or glutathione (GSH) conjugation activities while Cys-GSTs rather exhibit deglutathionylation and dehydroascorbate reductase activities. Some of them also appear to have non-catalytic ligandin properties for the transport or storage of various molecules. The plant-specific Tau GST (GSTU) class is usually the most expanded one. The GSTUs are often over-expressed during biotic and abiotic stresses contributing notably to herbicide detoxification. However, the physiological role of most GSTUs is still poorly documented in planta. By combining phylogenetic, biochemical and structural approaches, this work led to the characterization of nine GSTUs from Arabidopsis thaliana<\/em> (AtGSTUs) and six GSTUs from Populus trichocarpa<\/em> (PtGSTUs). Phylogenetic analysis of the Ser-GSTs present in photosynthetic organisms revealed that the expansion of GSTUs occurred concomitantly with the appearance of vasculature in plants, although some mosses and bryophytes possess GSTUs. Within an organism, GSTUs can be classified into distinct groups according to their catalytic motif. Enzymatic tests using recombinant proteins showed that almost all studied GSTUs exhibit GSH conjugation and peroxide reduction activities against different model substrates (CDNB, isothiocyanate derivatives, hydroperoxides). The three-dimensional structures of two GSTUs have been resolved and these adopt the classical canonical GST fold with some notable difference between them. The biochemical and structural analyses of these AtGSTUs and PtGSTUs further showed that some of them bind bacterial porphyrins while others bind polyphenolic compounds. Among the enzyme-ligand complexes identified, the structure of a baicalein-GSTU has been solved. The use of metabolites enriched samples extracted from A. thaliana<\/em> and P. trichocarpa<\/em> is the next step to decipher the role of GSTUs in planta.<\/p>\n","protected":false},"excerpt":{"rendered":"

Elodie Sylvestre-Gonon soutiendra sa th\u00e8se, intitul\u00e9e \u00ab Caract\u00e9risation biochimique et structurale de quelques glutathion transf\u00e9rases de la classe Tau d’arabette (Arabidopsis thaliana) et de peuplier (Populus trichocarpa) \u00bb, le mardi 1er d\u00e9cembre 2020 \u00e0 14h en visioconf\u00e9rence sur TEAMS. Ce … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[8],"tags":[],"class_list":["post-10614","post","type-post","status-publish","format-standard","hentry","category-thesis"],"_links":{"self":[{"href":"https:\/\/mycor.iam.inrae.fr\/IAM\/index.php?rest_route=\/wp\/v2\/posts\/10614","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mycor.iam.inrae.fr\/IAM\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mycor.iam.inrae.fr\/IAM\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mycor.iam.inrae.fr\/IAM\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mycor.iam.inrae.fr\/IAM\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=10614"}],"version-history":[{"count":0,"href":"https:\/\/mycor.iam.inrae.fr\/IAM\/index.php?rest_route=\/wp\/v2\/posts\/10614\/revisions"}],"wp:attachment":[{"href":"https:\/\/mycor.iam.inrae.fr\/IAM\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=10614"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mycor.iam.inrae.fr\/IAM\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=10614"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mycor.iam.inrae.fr\/IAM\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=10614"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}