{"id":8473,"date":"2017-11-30T21:07:23","date_gmt":"2017-11-30T21:07:23","guid":{"rendered":"https:\/\/mycor.iam.inrae.fr\/IAM\/?p=8473"},"modified":"2017-11-30T21:07:23","modified_gmt":"2017-11-30T21:07:23","slug":"phd-defense-n-valette","status":"publish","type":"post","link":"https:\/\/mycor.iam.inrae.fr\/IAM\/?p=8473","title":{"rendered":"PhD Defense : N. Valette"},"content":{"rendered":"
Nicolas Valette\u00a0soutiendra publiquement ses travaux de th\u00e8se portant sur :<\/div>\n
<\/div>\n
La caract\u00e9risation fonctionnelle de petites prot\u00e9ines s\u00e9cr\u00e9t\u00e9es chez les champignons lignolytiques<\/strong><\/div>\n
Dirig\u00e9s par M\u00e9lanie Morel-Rouhier et Eric Gelhaye<\/div>\n
le 6 d\u00e9cembre \u00e0 9h00,\u00a0amphith\u00e9\u00e2tre 14<\/div>\n
Facult\u00e9 des Sciences et technologies<\/div>\n
Vandoeuvre-les-Nancy<\/div>\n

R\u00e9sum\u00e9\u00a0:\u00a0<\/strong>Durant ces derni\u00e8res d\u00e9cennies, les syst\u00e8mes enzymatiques de d\u00e9gradation du bois s\u00e9cr\u00e9t\u00e9s par les champignons ont fait l\u2019objet de nombreuses \u00e9tudes aboutissant \u00e0 la caract\u00e9risation fonctionnelle et biochimique des enzymes extracellulaires majeures agissant directement sur le polym\u00e8re. Cependant, les syst\u00e8mes annexes associ\u00e9s au processus de d\u00e9gradation n\u2019ont \u00e0 l\u2019heure actuelle \u00e9t\u00e9 que peu \u00e9tudi\u00e9s. En particulier, les syst\u00e8mes de d\u00e9toxication et de r\u00e9ponses des champignons au stress g\u00e9n\u00e9r\u00e9 par le processus de d\u00e9gradation ainsi que les m\u00e9canismes lui permettant de cro\u00eetre dans cet environnement hostile sont encore peu connus. Ce stress est majoritairement d\u00fb \u00e0 la pr\u00e9sence de radicaux et d\u2019extractibles. Les extractibles sont des mol\u00e9cules issues du m\u00e9tabolisme secondaire de l\u2019arbre qui sont synth\u00e9tis\u00e9s pour augmenter la durabilit\u00e9 du bois face aux attaques biotiques et abiotiques. Une analyse transcriptomique r\u00e9alis\u00e9e au laboratoire a mis en \u00e9vidence la surexpression de g\u00e8nes codant des petites prot\u00e9ines s\u00e9cr\u00e9t\u00e9es (SSP) chez\u00a0Phanerochaete chrysosporium\u00a0<\/em>lors d\u2019une culture en pr\u00e9sence d\u2019extractibles de ch\u00eane. La fonction de ce type de prot\u00e9ines chez les champignons lignolytiques est inconnue. Mon projet de th\u00e8se a port\u00e9 sur la caract\u00e9risation d\u2019une de ces SSP (SSP1). Les r\u00e9sultats obtenus ont r\u00e9v\u00e9l\u00e9 des propri\u00e9t\u00e9s biochimiques atypiques pour cette prot\u00e9ine qui est capable de former une structure fibrillaire, notamment gr\u00e2ce \u00e0 la pr\u00e9sence d\u2019un domaine C-terminal riche en alanine et glycine. De plus, nous avons pu montrer que cette prot\u00e9ine pr\u00e9sentait une activit\u00e9 \u03b2-glucuronidase\u00a0in vitro,\u00a0<\/em>qui est d\u00e9pendante de son \u00e9tat d\u2019oligomerisation. Une approche physiologique a \u00e9galement \u00e9t\u00e9 abord\u00e9e gr\u00e2ce \u00e0 l\u2019obtention de mutants knock-out de SSP de\u00a0Podospora anserina<\/em>. La caract\u00e9risation de ces mutants a montr\u00e9 un d\u00e9faut de croissance en condition de stress oxydant et en pr\u00e9sence de mol\u00e9cules perturbant l\u2019int\u00e9grit\u00e9 de la paroi cellulaire. Enfin, une analyse\u00a0in silico\u00a0<\/em>des orthologues de SSP1 a montr\u00e9 la pr\u00e9sence de ce g\u00e8ne dans les g\u00e9nomes d\u2019organismes saprophytes, ectomycorhiziens ou pathog\u00e8nes sugg\u00e9rant un r\u00f4le indirect de cette prot\u00e9ine dans les processus de d\u00e9gradation du bois, probablement en lien avec la gestion du stress associ\u00e9.<\/p>\n

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Mots-clef\u00a0:\u00a0Phanerochaete chrysosporium<\/em>, petites prot\u00e9ines s\u00e9cr\u00e9t\u00e9es (SSP), d\u00e9gradation du bois, extractibles, saprophytes, stress<\/p>\n

 <\/p>\n

Abstract:\u00a0<\/strong>During the last decades, the enzymatic systems involved in wood degradation have been intensively studied in fungi. This has led to functional and biochemical characterization of the main extracellular enzymes that are involved in the process. However, other systems associated to the degradation mechanisms have been poorly studied. In particular, the detoxification and stress response pathways allowing the fungus to grow in and resist the toxic conditions that are associated to the degradative process are still unknown. This stress is mostly due to the presence of radicals and extractives. Extractives are putative toxic compounds produced as secondary metabolites in tree to enhance wood durability against biotic and abiotic attacks. A transcriptomic analysis performed in the laboratory highlighted the up-regulation of genes coding for small secreted proteins (SSP) in Phanerochaete chrysosporium<\/em> in presence of oak extractives. The functions of these SSP are unknown in lignolytic fungi. My PhD project was focused on the characterization of one of these SSP (namely SSP1) of P. chrysosporium<\/em>. The biochemical data revealed atypical features for SSP1. Indeed, it is able to form fibrilar structure, thanks to an alanine-rich and glycine-rich C-terminal domain. Moreover, we have shown that this protein exhibits \u03b2-glucuronidase activity in vitro<\/em> which is dependent on its oligomerization state. Physiological data were obtained thanks to the obtention of SSP knock-out mutants in Podospora anserina<\/em>. These mutants have growth defect in oxidizing stress condition and in presence of cell wall-disruptive compounds. Finally, the in silico<\/em> analysis of SSP1 orthologues revealed the presence of this gene in genomes of saprophytic, ectomycorrhizal or pathogenic fungi, suggesting an indirect role of this protein in wood degradation processes, probably linked to the associated stress.<\/p>\n

Key-words: Phanerochaete chrysosporium<\/em>, small secreted proteins (SSP), wood degradation, extractives, saprophytic fungi, stress<\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

Nicolas Valette\u00a0soutiendra publiquement ses travaux de th\u00e8se portant sur : La caract\u00e9risation fonctionnelle de petites prot\u00e9ines s\u00e9cr\u00e9t\u00e9es chez les champignons lignolytiques Dirig\u00e9s par M\u00e9lanie Morel-Rouhier et Eric Gelhaye le 6 d\u00e9cembre \u00e0 9h00,\u00a0amphith\u00e9\u00e2tre 14 Facult\u00e9 des Sciences et technologies Vandoeuvre-les-Nancy … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[],"class_list":["post-8473","post","type-post","status-publish","format-standard","hentry","category-seminarmeeting"],"_links":{"self":[{"href":"https:\/\/mycor.iam.inrae.fr\/IAM\/index.php?rest_route=\/wp\/v2\/posts\/8473","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\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/mycor.iam.inrae.fr\/IAM\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=8473"}],"version-history":[{"count":0,"href":"https:\/\/mycor.iam.inrae.fr\/IAM\/index.php?rest_route=\/wp\/v2\/posts\/8473\/revisions"}],"wp:attachment":[{"href":"https:\/\/mycor.iam.inrae.fr\/IAM\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=8473"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mycor.iam.inrae.fr\/IAM\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=8473"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mycor.iam.inrae.fr\/IAM\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=8473"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}