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Dernière mise à jour : Mai 2018

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Epigenetic, holocentrism and insect adaptation (EHA)

Introduction

Holocentric chromosomes are found in many organisms such as aphids, Heteroptera, nematodes, some wild plants and Lepidoptera. Such chromosomes lack a discernable centromere when observed during cell division. Rather, the kinetochores and the mitotic spindles are spread over the entire length of the chromosomes. The molecular nature of such centromeres remains poorly understood.
 

DAPI staining of metaphasic chromosomes in S. frugiperda eggs

DAPI staining of metaphasic chromosomes in S. frugiperda eggs

Our research team aims to decipher the holocentric structure of Lepidopteran chromosomes and understand its impact on gene regulation, on cell division and on evolution.
We are looking to develop methods affecting this fundamental property of chromosomes in order to induce developmental defects in pest moths such as Spodoptera frugiperda.
 
 
 
 
 
 
 
 
 
 
 
 
 

Results 2007- 2010

  • We have identified the repeat elements comprised within 4Mb of genomic sequence of S. frugiperda. We showed that the complexity of genomes is very variable from one species of holocentric insects to another (4 species studied). Nevertheless, we found that the LINE type retrotransposons and the TIRs transposons are always overrepresented.
  • We identified and started to map the epigenetic marks often associated to holocentric chromosomes. These are non-coding RNAs of the rasi (repeat associated small interfering DNA) type and post-translational modifications of histones associated to both euchromatin and heterochromatin.
  • We also started to characterize centromeric proteins homologs in S. frugiperda in order to identify their DNA targets.
  • Through a comparative genomics program, we showed that the mutation rate for Lepidopteran genomes (3 species studied) is greater than genomes of Dipteran of the same evolutionary distance.
Silk worms (B. mori), tomato moth (H. armigera) and Army worm (S. frugiperda)

Silk worms (B. mori), tomato moth (H. armigera) and Army worm (S. frugiperda)

 

Current and future projects

A genoscope grant has been awarded to an international consortium led by our lab to produce the complete genome sequence of our main pest model S. frugiperda. In addition, we are in the process of producing a genetic map based on microsatellites genotyping of F2 individuals (in collaboration with the CBGP laboratory of Baillarguet). We are continuing the analysis of the chromatin structure during the development of S. frugiperda and in response to its environment. Indeed, S. frugiperda is of particular interest becazuse it is found in the wild as two different morphs adapted to different host-plants. We want to understand better the specificities of this insect development and its adaptation in order to identify the genes that we could act upon to regulate the impact of damages on crop.
 

Funding

Led by EHA
  • ANR 2013-2016 ADA-SPODO (PI, Emmanuelle d’Alençon, INRA)
  • INRA SPE 2010-2012 Host variants polymorphism (PI, Emmanuelle d’Alençon, INRA)
  • Genoscope 2011 WGS Spodoptera frugiperda (PI, Philippe Fournier, INRA)
  • ANR 2007-2011 HOLOCENTRISM (PI, Philippe Fournier, INRA)
In collaboration
  • ANR 2014-2017 ADAPTOME (PI, Réjane Streiff, INRA-CBGP)
  • ANR 2007-2011 Gnp Annot (PI, Stéphanie Sidibe, CIRAD)
  • Genoscope 2007-2011 Lepidopteran synteny (PI, René Feyereisen, INRA)
  • INRA SPE 2007-2010 Function, origin and evolution of X-tox (PI, Jean-Michel Escoubas)

Consortia

  • ADALEP
  • Funded by the INRA department of Environment and Plant Health and coordinated by Emmanuelle D'Alençon. It comprises 23 French laboratories that focus on the biotic adaptation of Lepidopteran.