{"id":3172,"date":"2013-12-23T09:12:52","date_gmt":"2013-12-23T09:12:52","guid":{"rendered":"https:\/\/mycor.iam.inrae.fr\/IAM\/?p=3172"},"modified":"2013-12-23T09:15:36","modified_gmt":"2013-12-23T09:15:36","slug":"p","status":"publish","type":"post","link":"https:\/\/mycor.iam.inrae.fr\/IAM\/?p=3172","title":{"rendered":"PhD Defense : A. Vayssi\u00e8re"},"content":{"rendered":"

The defense will be held the\u00a013th January 2014<\/strong>\u00a0at\u00a013H30<\/strong>\u00a0in\u00a0Amphitheater 7,<\/strong>\u00a0Facult\u00e9 des Sciences<\/strong>, Boulevard des Aiguillettes, Vandoeuvre<\/p>\n

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Auxin control in poplar root development in response to the ectomycorrhizal fungus Laccaria bicolor<\/i><\/b><\/h1>\n

Root systems of host trees are known to establish the ectomycorrhizal (ECM) symbiosis with rhizospheric fungi. This mutualistic association leads to modifications of root development that including a stimulation of lateral host roots, and a modification in root growth. The phytohormone auxin (Indole-3-acetic acid, IAA) is known to regulate LRs formation and root growth. Our research focussed on auxin pathways in poplar root in response to L. bicolor<\/i>.<\/p>\n

In this study, our data showed that the poplar-Laccaria bicolor<\/i> interaction leads to the arrest of LRs and adventitious root growth after two weeks of interaction. We also showed that this arrest is not regulated by the Hartig net. Differential auxin responses were analyzed by using an auxin-responsive DR5::GUS<\/i> marker line and revealed a loss of auxin response in ECM roots. An oligoarray-based transcript profiling of poplar roots in contact with L. bicolor<\/i> highlights a differential expression of auxin asociated genes in ECM. Measurement of auxin metabolite in ECM and in the free living partners revealed an IAA accumulation, an activation of the IPyA (Indol-3-Pyruvic Acid) dependant IAA biosynthesis pathway in both partners, as well as changes in IAA conjugation pathways in poplar and in IAA degradation pathways in L. bicolor<\/i>. Our findings illustrate the impact of L. bicolor<\/i> colonization on root auxin metabolism and response, and also suggest a role of auxin as! a signal in the formation of ECM and in the regulation of ECM function.<\/p>\n

In parallel, PtaPIN9 function analysis in response to L. bicolor<\/i> has been performed. PtaPIN9 immunolocalization in poplar roots showed similar localization to AtPIN2 in epidermis cells. Transgenic lines having a modification in PtaPIN9<\/i> expression, did not formed new LRs in respond to L. bicolor<\/i>. In ECM roots, the loss of PtaPIN9 signal is observed but modifications of PtaPIN9<\/i> expression did not modify the root growth arrest and the Hartig net formation.<\/p>\n

These results show major changes in auxin associate pathways in poplar root by the symbiotic fungus L. bicolor<\/i>, during the formation of the mycorrhiza root. Our results offer perspectives on the role of auxin in root development and in the context plants-microbes interactions.<\/p>\n

Keywords<\/i>: Root architecture, Auxin, Mycorrhiza, Lateral root, Root growth, Poplar, Laccaria bicolor<\/i><\/p>\n

Contr\u00f4le de l\u2019auxine dans les modifications du d\u00e9veloppement racinaire du peuplier en r\u00e9ponse au champignon ectomycorhizien, Laccaria bicolor<\/i><\/b><\/h1>\n

Le syst\u00e8me racinaire des arbres peut \u00e9tablir des symbioses ectomycorhiziennes (ECM) avec des champignons rhizosph\u00e9riques. La mise en place de la symbiose est accompagn\u00e9e d\u2019une stimulation de la formation des racines lat\u00e9rales (RLs), et d\u2019une modification de la croissance racinaire. Ces processus d\u00e9veloppementaux conduisent \u00e0 la formation de racines courtes typiques des ECMs. Il a \u00e9t\u00e9 montr\u00e9 que l\u2019auxine est une phytohormone clef dans la formation des RLs ainsi que dans la croissance racinaire. Notre projet s\u2019est focalis\u00e9 sur l\u2019\u00e9tude de la r\u00e9gulation des voies de l\u2019auxine dans la racine de peuplier en r\u00e9ponse \u00e0 L. bicolor.<\/i><\/p>\n

Dans cette \u00e9tude, nous avons mis en \u00e9vidence un arr\u00eat de croissance des RLs et des racines adventives du peuplier Populus tremula<\/i> x P. alba<\/i>, apr\u00e8s deux semaines de co-culture avec L. bicolor<\/i>. De plus, nous avons aussi montr\u00e9 que cet arr\u00eat n\u2019est pas conditionn\u00e9 par la pr\u00e9sence du r\u00e9seau de Hartig. Une analyse de l\u2019expression globale des g\u00e8nes de peuplier dans la mycorhize a \u00e9t\u00e9 r\u00e9alis\u00e9e au cours de la formation de la mycorhize. Cette analyse, coupl\u00e9e \u00e0 des observations du gradient auxinique via<\/i> le patron d\u2019expression du promoteur DR5, montre que la signalisation auxinique est affect\u00e9e dans l\u2019organe symbiotique. La quantification de l\u2019auxine (acide indole 3-ac\u00e9tique, AIA) et des m\u00e9tabolites associ\u00e9s a permis de mettre en \u00e9vidence un envir! onnement symbiotique riche en auxine dans la mycorhize, qui pourrait expliquer les modifications de la signalisation auxinique. De plus, un changement de la conjugaison et de la d\u00e9gradation de l\u2019AIA est d\u00e9tect\u00e9 dans la racine, ainsi qu\u2019une d\u00e9gradation de l\u2019AIA dans les hyphes de L. bicolor.<\/i><\/p>\n

En parall\u00e8le, une analyse fonctionnelle de PtaPIN9, un orthologue de AtPIN2, responsable du transport basip\u00e8te de l\u2019auxine \u00e0 l\u2019apex racinaire chez Arabidopsis thaliana<\/i>, a \u00e9t\u00e9 r\u00e9alis\u00e9e au cours de la mycorhization avec L. bicolor.<\/i> L\u2019immunolocalisation de PtPIN9 dans les racines de peuplier a montr\u00e9 une localisation similaire \u00e0 AtPIN2, dans les cellules \u00e9pidermiques.<\/i> Les lign\u00e9es transg\u00e9niques ayant une modification de l\u2019expression de ce g\u00e8ne ne r\u00e9pondent pas \u00e0 L. bicolor<\/i> en terme de stimulation de RLs. Dans les racines mycorhiz\u00e9es, PtaPIN9 n\u2019est plus observ\u00e9e, mais les modifications de l\u2019expression de PtaPIN9<\/i> ne modifient ni l\u2019arr\u00eat de croissance racinaire, ni la formation du r\u00e9seau de Hartig.<\/p>\n

Ces r\u00e9sultats montrent des modifications majeures des voies de l\u2019auxine du peuplier par le champignon symbiotique L. bicolor.<\/i> Cette \u00e9tude ouvre des perspectives sur la compr\u00e9hension du r\u00f4le de l\u2019auxine dans le d\u00e9veloppement racinaire ainsi que dans le contexte des interactions plantes-microorganismes.<\/p>\n

Mots-cl\u00e9s<\/i>\u00a0: Architecture racinaire, Auxine, Mycorhize, Racines lat\u00e9rales, croissance racinaire, Peuplier, Laccaria bicolor<\/i><\/p>\n","protected":false},"excerpt":{"rendered":"

The defense will be held the\u00a013th January 2014\u00a0at\u00a013H30\u00a0in\u00a0Amphitheater 7,\u00a0Facult\u00e9 des Sciences, Boulevard des Aiguillettes, Vandoeuvre Auxin control in poplar root development in response to the ectomycorrhizal fungus Laccaria bicolor Root systems of host trees are known to establish the ectomycorrhizal … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[],"class_list":["post-3172","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\/3172","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=3172"}],"version-history":[{"count":0,"href":"https:\/\/mycor.iam.inrae.fr\/IAM\/index.php?rest_route=\/wp\/v2\/posts\/3172\/revisions"}],"wp:attachment":[{"href":"https:\/\/mycor.iam.inrae.fr\/IAM\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=3172"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mycor.iam.inrae.fr\/IAM\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=3172"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mycor.iam.inrae.fr\/IAM\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=3172"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}