Know more

About cookies

What is a "cookie"?

A "cookie" is a piece of information, usually small and identified by a name, which may be sent to your browser by a website you are visiting. Your web browser will store it for a period of time, and send it back to the web server each time you log on again.

Different types of cookies are placed on the sites:

  • Cookies strictly necessary for the proper functioning of the site
  • Cookies deposited by third party sites to improve the interactivity of the site, to collect statistics

Learn more about cookies and how they work

The different types of cookies used on this site

Cookies strictly necessary for the site to function

These cookies allow the main services of the site to function optimally. You can technically block them using your browser settings but your experience on the site may be degraded.

Furthermore, you have the possibility of opposing the use of audience measurement tracers strictly necessary for the functioning and current administration of the website in the cookie management window accessible via the link located in the footer of the site.

Technical cookies

Name of the cookie

Purpose

Shelf life

CAS and PHP session cookies

Login credentials, session security

Session

Tarteaucitron

Saving your cookie consent choices

12 months

Audience measurement cookies (AT Internet)

Name of the cookie

Purpose

Shelf life

atid

Trace the visitor's route in order to establish visit statistics.

13 months

atuserid

Store the anonymous ID of the visitor who starts the first time he visits the site

13 months

atidvisitor

Identify the numbers (unique identifiers of a site) seen by the visitor and store the visitor's identifiers.

13 months

About the AT Internet audience measurement tool :

AT Internet's audience measurement tool Analytics is deployed on this site in order to obtain information on visitors' navigation and to improve its use.

The French data protection authority (CNIL) has granted an exemption to AT Internet's Web Analytics cookie. This tool is thus exempt from the collection of the Internet user's consent with regard to the deposit of analytics cookies. However, you can refuse the deposit of these cookies via the cookie management panel.

Good to know:

  • The data collected are not cross-checked with other processing operations
  • The deposited cookie is only used to produce anonymous statistics
  • The cookie does not allow the user's navigation on other sites to be tracked.

Third party cookies to improve the interactivity of the site

This site relies on certain services provided by third parties which allow :

  • to offer interactive content;
  • improve usability and facilitate the sharing of content on social networks;
  • view videos and animated presentations directly on our website;
  • protect form entries from robots;
  • monitor the performance of the site.

These third parties will collect and use your browsing data for their own purposes.

How to accept or reject cookies

When you start browsing an eZpublish site, the appearance of the "cookies" banner allows you to accept or refuse all the cookies we use. This banner will be displayed as long as you have not made a choice, even if you are browsing on another page of the site.

You can change your choices at any time by clicking on the "Cookie Management" link.

You can manage these cookies in your browser. Here are the procedures to follow: Firefox; Chrome; Explorer; Safari; Opera

For more information about the cookies we use, you can contact INRAE's Data Protection Officer by email at cil-dpo@inrae.fr or by post at :

INRAE

24, chemin de Borde Rouge -Auzeville - CS52627 31326 Castanet Tolosan cedex - France

Last update: May 2021

Menu Institut Sophia Agrobiotech Logo Marque Etat - République Française Logo_INRAE_noir Logo Université Côte d'Azur CNRS

Home page

Institut Sophia Agrobiotech

UMR INRA - Univ. Nice Sophia Antipolis - Cnrs

http://www.paca.inra.fr/institut-sophia-agrobiotech_eng/

Soutenance de thèse - Rahim HASSANALY GOULAMHOUSSEN

Lundi 13 Décembre 2021 - 13:30 - Visioconférence par ZOOM

Soutenance de thèse
Rahim HASSANALY GOULAMHOUSSEN : "Etude de l'implication des mécanismes épigénétiques chez le nématode à galles Meloidogyne incognita"

devant le jury composé de :

Président/te du jury :

  • Cécile SABOURAULT, Professeure, ECOSEAS, Université Côte d'Azur, France

Rapporteurs/trices :

  • Nadia PONTS, Chargée de Recherche, MycSA, INRAE Bordeaux, France
  • Marc-Henri LEBRUN, Directeur de Recherche, INRAE Grignon, France

Examinateurs/trices :

  • Rita REBOLLO, Chargée de Recherche, INSA Lyon, France
  • Eric GRENIER, Chargé de Recherche, IGEPP Le Rheu, France
  • Eric ROTTINGER, Directeur de Recherche, IRCAN, Université Côte d'Azur, France

Directeur/trice de Thèse :

  • Laetitia ZURLETTO, Maîtresse de Conférences Universitaire, ISA , Université Côte d'Azur, France
  • Pierre ABAD, Directeur de Recherche, ISA, Université Côte d'Azur, France

Abstract :

Plant parasitic nematodes of the genus Meloidogyne are crop pests of global importance. As such, M. incognita is the emblematic species as it is present all over the world with a wide spectrum of host plants. Currently, the use of resistant plants is the most effective way to control this nematode. However, the emergence of virulent lines able to bypass the plant resistance requires a better understanding of the biology of this species. M. incognita reproduces asexually by obligate mitotic parthenogenesis. Asexual reproduction is often considered as an evolutionary dead end because in this case, individuals adapt poorly to changing environments, due to the absence of meiosis. Despite this apparent lack of genetic plasticity, this species shows an amazing ability to adapt to adverse environments. An example of this is the bypassing of resistance in response to selection pressure exerted by the tomato Mi-1 resistance gene, with the appearance of virulent phenotypic variants in the progeny. The characteristics of the transmission of this trait over generations suggest a non-Mendelian heritability, thus involving an epigenetic component.

In this thesis, the impact of histone post-translational modifications (HPTMs) in the biology of M. incognita was studied. First, the method of chromatin immunoprecipitation in fixed condition was developed and optimized for M. incognita. This optimization, performed for the first time in a parasitic nematode, allowed to show the involvement of five HPTMs in the regulation of genome expression. The conservation of the function of H3K9me3, through its association with transposable elements and low-expressed genes, and of H3K4me3 enriched at the promoter level of highly expressed genes, leads to the hypothesis of the existence of a "histone code" in this species.

The dynamics of the chromatin landscape was studied during the development of this nematode, through the analysis of the regulation of the five HPTMs. These dynamics are marked by the expression of specific genes in association with the activating HPTM H3K4me3, during the transition from the egg stage to the L2 juvenile larval stage. At the egg stage, the predicted functions of the genes regulated by this mark concern cell cycle regulation and embryo development, while at the L2 juvenile larval stage, mainly genes involved in stimulus response were identified.

The importance of HPTMs in the acquisition of virulence of this nematode was also initiated. The identification of differential enrichment profiles between avirulent and virulent lines of M. incognita showed a virulence polymorphism related to the regulation by HPTMs. At the origin of this polymorphism are a class of genes coding for SKP1 proteins, involved in protein degradation pathways. These candidate genes show overexpression in association with H3K4me3 in avirulent lines and decreased expression associated with loss of this HPTM in virulent lines. The precise role of SKP1 proteins in the acquisition of virulence in M. incognita remains to be determined.

All these works contribute to evaluate the importance of epigenetic mechanisms in the adaptation of parthenogenetic organisms to changing environments and to define new control methods against crop pests.

Keywords :

epigenetics, HPTM, root-knot nematode, Meloidogyne incognita, development, virulence