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Recherche du rôle des MSL dans les poils racinaires lors de la mise en place de la symbiose fixatrice d'azote chez Medicago truncatula

Abstract : The first steps of symbiosis occurring between Legumes and microorganisms are highly regulated processes, both at the molecular level and at the cellular level. During symbiosis with nitrogen fixing bacteria, called rhizobia, these modifications occur in root hairs. Several arguments have shown that mechanical constraints may regulate these steps. Hence, the involvement of physical sensors during these early events is worth considering. We focused here on one of these sensor families, the MSL (MscS-Like). These proteins are channels able to open upon mechanical stretching. We look for their role during first steps of symbiosis between the model Legumes Medicago truncatula and rhizobia. In silico studies of M. truncatula's genome allowed us to define a MtMSL family. Transcript analyses showed that only two of them were expressed in root hairs: MtMSL2.1 and MtMSL2.4, the latter being the most expressed. However, this expression is not modified by Nod factor treatments; molecules produced by rhizobia that induces the first symbiotic signalization steps. In parallel, confocal microscopy analyses show plasma membrane and endomembrane localization of MtMSL2.4. Moreover, electrophysiological measurements confirmed that this candidate is a high conductance channel mechanically activated. Finally, we performed several phenotypical studies with Mtmsl2.4 mutants in different conditions. No differences were observed between the mutants and WT during rhizobia symbiotic interaction and root growth. There were also no differences observed in root hair development, for which a partly automatic measurement system was set up. These results suggest MtMSL2.4 may have a role in other phenomena, which could be interesting to understand further.
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Submitted on : Thursday, October 5, 2017 - 3:17:06 PM
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Marjorie Guichard. Recherche du rôle des MSL dans les poils racinaires lors de la mise en place de la symbiose fixatrice d'azote chez Medicago truncatula. Organisation et fonctions cellulaires [q-bio.SC]. Université Paris Saclay (COmUE), 2017. Français. ⟨NNT : 2017SACLS143⟩. ⟨tel-01611129⟩

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