CNET 2019 gathers researchers with interests on topics related to transposable element biology, including molecular and cellular mechanisms, physiological impacts on organisms, comparative genomics, population & evolutionary studies, and ecology. This is the 22nd annual meeting organized by the French research community working on transposable elements and will take place this year in Lyon, in the Rhone valley of France.
We invite interdisciplinary contributions including molecular, genetics and cellular studies, as well as bioinformatics and mathematical modelling approaches, applied to a wide range of model organisms (prokaryotes, plants, yeast, insects, ciliates, vertebrates,...). The programme will include invited talks, selected talks and ample time for poster presentation and discussions. Junior researchers are encouraged to apply for oral presentations.
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When will the conference take place
22nd National Congress on Transposable Elements (CNET-2019)
The role of natural transposable element insertions in stress response
Transposable elements are ubiquitous, abundant, and active components of genomes. Most of the mutations caused by transposable elements are most likely deleterious or neutral. However, transposable elements have also been shown to induce adaptive mutations. Our lab focuses on elucidating the role of those TEs involved in adaptation. While most studies so far have analyzed reference TE insertions, we are currently generating new reference genomes that will allow us to investigate insertions beyond those present in a single North American strain. To detect, annotate, and analyze TE insertions, we are using the REPET package. As a proof of concept, we have re-annotated the reference genome, and have identified 2.7x more TEs than previously annotated. The combined analysis of the 13 new reference genomes revealed additional TE copies from 26 families that were not previously identified in Drosophila melanogaster, and several unknown, putatively new, families. We are currently investigating the potential role of these insertions in three ecologically relevant traits: insecticide resistance, tolerance to heavy metals, and desiccation tolerance. Indeed, an initial analysis has shown that TEs are likely to contribute a significant fraction of stress-related transcription factor binding sites in D. melanogaster and humans.
The rapid evolution of small RNA pathways and DNA methylation targeting transposons in arthropods
In the Drosophila germline, small RNA molecules termed PIWI-interacting RNAs (piRNAs) silence transposable elements (TEs), protecting the germline from genomic instability and mutation. In the soma, TEs are silenced by another class of small RNAs called siRNAs. We have found that this difference between the germline and soma is a recent evolutionary quirk of Drosophila, and analysis of 20 species across the arthropod phylum suggests that somatic piRNAs targeting TEs and messenger RNAs are common among arthropods. The presence of an RNA-dependent RNA polymerase in chelicerates (horseshoe crabs, spiders and scorpions) suggests that arthropods originally used a plant-like RNA interference mechanism to silence TEs. In mammals and plants, cytosine methylation plays an important role in silencing TEs. This DNA methylation machinery is missing from Drosophila, but in other arthropods TEs are targeted by methylation.
Despite eliciting host immunity, several viruses establish chronic, often life-long infection in humans that can affect immune function. The ultimate form of parasitism and evasion of host immunity is for the virus genome to enter the germ line of the host. Retroviruses have invaded the host germ line on the grandest scale, and this is evident in the extraordinary abundance of endogenous retroelements in the genome of all vertebrate species that have been studied. Recent studies suggests that such viral endogenisation events continue to shape host immunity over long evolutionary times and through diverse mechanisms, including triggering host innate and adaptive immune responses or regulating immune gene expression or function. Although recent integrations may be more detrimental to host immunity, evidence will be presented that integrations acquired millions of years ago were positively selected and continue to shape host immunity in humans.
Institut de Biologie de l'Ecole Normale Supérieure
Paris, France
Transcriptional control of immune-responsive genes by DNA methylation and demethylation and its relevance in antibacterial defense
In plants, small non-coding RNAs can guide DNA methylation of transposable elements (TEs) as well as repeat. This phenomenon is referred to as RNA-directed DNA methylation (RdDM) and contributes to the transcriptional repression of some developmentally and stress-regulated genes that carry TE-derived repeats in their vicinity. We have previously shown that the RdDM pathway negatively regulates the Arabidopsis immune response raised against a phytopathogenic Pseudomonas syringae strain. Accordingly, we have identified a subset of defense genes that are targeted and repressed by RdDM, presumably to prevent trade-off effects that would be caused by their constitutive expression and/or sustained induction. Some of these genes are also concomitantly demethylated in their promoters through an active DNA demethylation process, which often targets TE/repeat-boundaries. The latter process ensures the rapid and pervasive induction of these defense genes upon pathogen detection. Here, I will present the extent to which the Arabidopsis active demethylase ROS1 reprograms the Arabidopsis transcriptome during antibacterial defense. I will also report on the detailed mechanisms by which ROS1 facilitates the transcriptional activation of specific immune receptors. Finally, I will provide evidence that modulation of active demethylation activity is essential to fine-tune the plant immune response in nature, presumably to promote adaptation to specific environment.
WATCH OUT: tram T1 is not operating any more during this Summer AND M° B (blue line) is replaced by buses after 21:15 from Monday 8th to Wednesday 10th.
