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Doctoral thesis
English

Comprehensive Study of the Fungal Endophyte Community of the Long-lived Amazonian Palm Astrocaryum Sciophilum: A Model for Deciphering Plant-microbe Interactions at Chemical and Bioactive Levels

Number of pages409
Imprimatur date2022-09-20
Defense date2022-03-11
Abstract

It is now established that plants are not distinct entities, but have evolved in association with highly complex and diverse microbial assemblages. These plant microbial symbiont communities (microbiota) and their collective genetic material constitute the plant microbiome, thought to play key roles in plant ecology and physiology, including plant fitness (growth and survival). Our interest is turned towards some of the fungal inhabitants of the microbiome: endophytic fungi. Endophytes colonize the healthy internal tissues of plants in an asymptomatic way and have been extensively studied in the last decades for their ability to produce bioactive molecules as part of a defense response against pathogens for the host or for the fungi themselves.

In this thesis, carried out in the scope of the Franco-Swiss project SECIL (Study of Endophyte Communities In a Leaf, SECIL_ANR), we aimed to study microbial crosstalk in plant leaf fungal endophytes at the chemical and bioactive level, searching for biologically relevant metabolites.

The typical palm tree from the primary forest in French Guiana, Astrocaryum sciophilum (Miq.) Pulle was chosen for deep investigations as a host model, due to its remarkable long-life cycle and the diversity of endophytic communities found in its leaves. Its long maturation age suggests that this palm might maintain a stable association with microbial communities over a substantial period of time. This implies that potential endophytes are able to survive and resist the environment of the plant, likely by developing antipathogens and cytotoxic metabolites involved in the longevity of the shoots and leaves of the palm. Moreover, the highly competitive rainforest ecosystem makes the selection pressure intense, probably prompting the microbes associated with this tropical host to produce interesting chemical entities. We also hypothesized that reciprocal chemical interactions occur between plant and fungi, via specialised chemistry potentially expressed in host tissues. We thus developed a strategy to study at a given time, this plant-fungi interaction from a molecular point-of-view, in the most comprehensive way possible, along with the bioactive potential which results from the interaction.

The workflow we developed in this thesis aims to take a metabolomic snapshot of the host leaf and its fungal endophytic community and study molecular interplay and reciprocal chemical interactions between them. We further exploited when possible specialised metabolites of the fungal community for their bioactivity (antivirulence or anticancer).

It allowed more particularly to characterise the metabolome of the fungal community and that of the host plant. The in-depth analysis of these data revealed interactions never before analysed in such a detailed and untargeted manner at the level of a host-leaf model. Our workflow also led to the identification of 24 new secondary metabolites of a Lasiodiplodia venezuelensis strain. Some of which showed interesting quorum sensing inhibition activity, with effect on the quorum sensing- regulated genes and some virulence factors, a minor compound showed significant and specific inhibition of Wnt activity and of the proliferation of Triple Negative Breast Cancer cell lines.

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Funding
  • French National Research Agency (ANR) - Study of leaf endophytic fungi: Exploration and valorization of biosourCed Innovative antibacterial metaboLites [ANR-15-CE21-0016]
Citation (ISO format)
PELLISSIER, Léonie. Comprehensive Study of the Fungal Endophyte Community of the Long-lived Amazonian Palm <i>Astrocaryum Sciophilum</i>: A Model for Deciphering Plant-microbe Interactions at Chemical and Bioactive Levels. 2022. doi: 10.13097/archive-ouverte/unige:166376
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Thesis
accessLevelRestrictedaccessLevelPublic 02/01/2026
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Creation01/24/2023 4:17:00 PM
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Status update03/16/2023 10:29:19 AM
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