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Les voies de signalisation des phytohormones dans l’établissement de la symbiose ectomycorhizienne entre racines de Populus et Laccaria bicolor : un nouveau regard sur la modulation de la perception de l’acide jasmonique au cours de la colonisation fongique

Abstract : Promoting nutrient cycling and tree fitness, ectomycorrhizae (ECM) are mutualistic interactions pivotal in forest ecosystems. However not much is known about the signals and molecular mechanisms underpinning their establishment. Using Populus and Laccaria bicolor as a model system, it was shown that the fungal Mycorrhiza-Induced Small Secreted Protein of 7 kDa (MiSSP7) is secreted upon ECM establishment, penetrates the nuclei of cortical root cells of its host and stabilizes the repressor of jasmonic acid (JA) signaling PtJAZ6, dampening plant responses to JA and promoting mutualism. JA signaling is implied in plant defense and development, but it is currently unknown which part of JA-dependent responses in host roots need to be suppressed for ECM formation. Therefore, the thesis aims to answer the following questions: (i) how does the effector protein MiSSP7 impact the structure of the JA perception complex in poplar roots? (ii) do distinct branches of JA signaling play specific roles during ECM establishment? (iii) does the interplay between JA signaling and other hormone signaling pathways influence symbiotic development? Through protein-protein interaction studies, we deciphered the composition of the PtJAZ6-associated protein complex in poplar roots and showed that MiSSP7 modulates the strength of interactions between PtJAZ6 and its associated transcription factors (TFs). Altered expression of the genes coding for such TFs in poplar roots, through genetic engineering, influences ECM maturation, indicating that PtJAZ6-binding TFs regulate the extent of this mutualistic interaction. In addition, by means of hormonomics coupled with physiologic and transcriptomic analysis of hormone-treated poplar roots and L. bicolor mycelium, we demonstrate that a complex rearrangement of phytohormone biosynthesis and perception takes place in host roots during symbiotic development. In particular, we found that fungus-colonized roots are less sensitive to JA. Altogether, our results suggest a dual role of JA signaling in developing ECM, with one branch functioning to regulate fungal apoplastic penetration to an optimal extent, and another being responsible of fungal exclusion under stress conditions. We propose that finely tuned phytohormone signaling, and in particular JA signaling, is crucial for the integration of fungal and plant-derived signals, in order to reprogram root and mycelial physiology for a successful mutualistic interaction.
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Theses
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http://docnum.univ-lorraine.fr/ulprive/DDOC_T_2019_0242_BASSO.pdf
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https://hal.univ-lorraine.fr/tel-02555772
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Submitted on : Monday, April 27, 2020 - 3:51:13 PM
Last modification on : Thursday, January 7, 2021 - 3:47:12 PM

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  • HAL Id : tel-02555772, version 1

Citation

Veronica Basso. Les voies de signalisation des phytohormones dans l’établissement de la symbiose ectomycorhizienne entre racines de Populus et Laccaria bicolor : un nouveau regard sur la modulation de la perception de l’acide jasmonique au cours de la colonisation fongique. Biologie végétale. Université de Lorraine, 2019. Français. ⟨NNT : 2019LORR0242⟩. ⟨tel-02555772⟩

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