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Analyse fonctionnelle d'effecteurs fongiques impliqués dans le développement de la symbiose ectomycorhizienne Laccaria bicolor-Populus trichocarpa

Abstract : Roots of most trees form symbiosis with mutualistic soil-borne fungi. The ectomycorrhizal basidiomycete Laccaria bicolor (Maire) P.D. Orton relies on mycorrhizal-induced small secreted proteins (MiSSP) to establish symbiotic tissues in the host-plant. The host proteins targeted by these fungal effectors are yet unknown. In the present study, we used the binary yeast two-hybrid (Y2H) system to determine direct interactions between MiSSP7 and the plant proteins in the L. bicolor-P. trichocarpa ectomycorrhizae. We showed that MiSSP7 interact with the jasmonic acid (JA) co-receptors JAZ5 and JAZ6 of P. trichocarpa, blocking JA signaling and promoting mutualism. L. bicolor transformants with severely reduced expression of MiSSP7 did not enter into symbiosis with poplar roots, a phenotype that could be complemented by transgenically varying the transcription of PtJAZ6 or through inhibiting JA signalling. Additional Y2H assays showed that PtJAZ6 protein form a regulatory complex involving 14-3-3 protein(s) and MYC transcriptional factors. Two others L. bicolor effectorlike proteins, MiSSP8 and MiSSP17, are secreted and are essential for the symbiosis development. MiSSP8 showed parietal and plasmalemma localization, while MiSSP17 was mainly cytoplasmic. Y2H assays suggested that these MiSSPs interact with plant proteins involved in plant defence signalling pathways. During symbiosis development, L. bicolor experiences important genetic reprogramming required for root colonization. Transcription factors (TFs) are key players of these genetic changes. Here, we developed high throughput analysis of TFs in L. bicolor to obtain a comprehensive inventory of significantly regulated transcription factors in ECM and showed that some of them display similarities with TFs involved in cell wall integrity, carbon, nitrogen, iron and sulfur metabolism. In addition, Yeast One Hybrid assays allowed the functional validation of 6% of the TFs predicted in silico and the identification of Secreted Transcriptional Activator Proteins (STAP) which may be a new class of effectors promoting symbiosis development or/and controlling rhizospheric microorganisms.
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  • HAL Id : tel-02811259, version 1
  • PRODINRA : 277639

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Yohann Daguerre. Analyse fonctionnelle d'effecteurs fongiques impliqués dans le développement de la symbiose ectomycorhizienne Laccaria bicolor-Populus trichocarpa. Sciences du Vivant [q-bio]. Université de Lorraine, 2013. Français. ⟨tel-02811259v1⟩

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