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Reference : UMR5546-PIEDEL-001
Workplace : CASTANET TOLOSAN
Date of publication : Friday, June 19, 2020
Scientific Responsible name : Pierre-Marc Delaux
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2020
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
Interactions between organisms are essential at all biological levels: from the origin of the eukaryotes to the functioning of extant and past ecosystems. These associations range in their outcome from parasitism (one partner benefits while the other is negatively affected) to mutualism (both partners benefit). From an evolutionary point of view, selection in the host organisms will favour the maintenance of mutualism over times and by contrast will support strategies to limit infection by parasites. At the genetic level, this should result in a high degree of conservation of genes involved in mutualism and in a high degree of polymorphism of genes favouring resistance to pathogens, even at the scale of a single species. In turn, this would imply that parasites will evolve infection strategies targeting highly conserved genes, such as those involved in mutualism.
In land plants, a major finding from comparative phylogenomic approaches was that plants species or clades which have maintained mutualism with microorganisms show a striking sequence conservation of genes involved in symbiosis establishment, while those which have abandoned mutualism lost these genes. In parallel, Genome-Wide Associations Studies (GWAS) led to the identification of genes linked to resistance or susceptibility to pathogens within populations of angiosperm species. Lastly, genetic analyses in model plants have shown that genes first characterized as central to symbioses establishment play major roles in plant susceptibility or resistance to pathogens. Given these empirical supports and the fact that most plant species are constantly interacting with both mutualistic and parasitic microorganisms, we hypothesize that mutualism and parasitism could influence each other over micro- and macro-evolutionary time scales. The goal of the thesis project is to test this hypothesis.
The hired student will identify in the liverworts Marchantia genes involved in parasitism or mutualism using genetic approaches (GWAS, selection scans) and will compare their evolution within species of two deeply divergent clades of land plants, angiosperms and liverworts. Then, through phylogenomic approaches across the entire embryophyte phylogeny, the hired student will describe the evolution of these genes and infer selective processes to understand how selection can manage the interplay between mutualism and parasitism.
The hired PhD student will have a Master in Bioinformatics, with skills in genomics, biostats, phenotypic data analysis, and strong interest in evolutionary biology and genetics. Practical skills: R software, Unix / Linux environment, and a programming language would be appreciated (python,..).
This interdisciplinary thesis project will be supervised by researchers experts in genetics (Maxime Bonhomme, LRSV Toulouse), in phylogenomics (Hervé Philippe, SETE Moulis) and in the evolution of plant–microbe interactions (Pierre-Marc Delaux, LRSV Toulouse). This project is supported by the 80|PRIME CNRS initiative, an initiative supporting interdisciplinary research across institutes (INSB and INEE). The student will be based at the LRSV lab and will do a number of secondments at the SETE lab.
The LRSV (Laboratoire de Recherche en Sciences Végétales, UMR5546) is a joint unit between the CNRS and the University of Toulouse III – Paul Sabatier. The LRSV hosts eight research teams focussed on plant signalling, plant development and plant – microbe interactions. The student will join the team “Evolution of Plant – Microbe interactions” led by Pierre-Marc Delaux.
SETE (Station d'Ecologie Théorique et Expérimentale) is a joint unit between the CNRS and the University of Toulouse III – Paul Sabatier. Located in the Pyrenees at one hour from Toulouse, SETE hosts 70 researchers, technicians, students and administrative staff.
The LRSV and SETE are part of the Labex TULIP.
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