{"id":16982,"date":"2023-09-29T09:31:40","date_gmt":"2023-09-29T07:31:40","guid":{"rendered":"https:\/\/www.egce.universite-paris-saclay.fr\/?p=16982"},"modified":"2023-09-29T09:31:41","modified_gmt":"2023-09-29T07:31:41","slug":"sujet-de-stage-m2-2024","status":"publish","type":"post","link":"https:\/\/www.egce.universite-paris-saclay.fr\/?p=16982","title":{"rendered":"Sujet de stage M2 2024"},"content":{"rendered":"\n

Analyse g\u00e9n\u00e9tique de la d\u00e9tection des oligosaccharides chez Drosophila melanogaster<\/em><\/h1>\n\n\n\n

Les drosophiles se nourrissent de microorganismes comme les levures, qu\u2019elles trouvent sur les fruits pourrissants, mais aussi des divers nutriments issus de ces fruits, comme les glucides, qu\u2019elles appr\u00e9cient. Elles sont capables de dig\u00e9rer l\u2019amidon, gr\u00e2ce \u00e0 une enzyme, l\u2019alpha-amylase, mais elles ne per\u00e7oivent pas le go\u00fbt de l\u2019amidon lui-m\u00eame. Leur syst\u00e8me sensoriel gustatif est connu pour leur permettre de d\u00e9tecter des sucres simples (glucose, fructose) ou des dim\u00e8res (maltose) gr\u00e2ce \u00e0 9 r\u00e9cepteurs gustatifs (sur un ensemble de 60).<\/p>\n\n\n\n

Nous avons r\u00e9alis\u00e9 une s\u00e9rie d\u2019observations comportementales et \u00e9lectrophysiologiques pour \u00e9valuer la capacit\u00e9 de d\u00e9tection de polym\u00e8res de glucose (G1 \u00e0 G12) chez les adultes de cette esp\u00e8ce. Alors que nous nous attendions \u00e0 trouver une meilleure sensibilit\u00e9 pour G1 (glucose) et G2 (maltose) et \u00e0 une diminution progressive de la sensibilit\u00e9 en fonction de la longueur du polym\u00e8re, nous avons observ\u00e9 au contraire une sensibilit\u00e9 croissante jusqu\u2019\u00e0 G5 puis une d\u00e9croissance jusqu\u2019\u00e0 G12. Ce r\u00e9sultat est difficile \u00e0 expliquer, notamment en ce qui concerne le m\u00e9canisme de d\u00e9tection. Une telle d\u00e9tection supposerait en effet que les mouches soient \u00e9quip\u00e9es de r\u00e9cepteurs gustatifs poss\u00e9dant soit un site r\u00e9cepteur de taille suffisante pour \u00ab accueillir \u00bb une grosse mol\u00e9cule comme G5, soit une coop\u00e9ration entre plusieurs r\u00e9cepteurs soit encore, l\u2019intervention d\u2019une enzyme de d\u00e9gradation des polym\u00e8res de glucose avec un m\u00e9canisme d\u2019action tr\u00e8s rapide.<\/p>\n\n\n\n

Afin de d\u00e9terminer quels sont les m\u00e9canismes mis en \u0153uvre, nous proposons une approche g\u00e9nomique bas\u00e9e sur l\u2019\u00e9tude de la variabilit\u00e9 g\u00e9n\u00e9tique existante au sein de populations de drosophiles. Cette d\u00e9marche s\u2019appuie sur un outil, le Drosophila Genetic Reference Panel (DGRP) qui comprend 200 lign\u00e9es iso-femelles de drosophiles provenant d\u2019une population de mouches captur\u00e9es sur un march\u00e9 aux \u00c9tats-Unis, dont le g\u00e9nome de chaque lign\u00e9e a \u00e9t\u00e9 s\u00e9quenc\u00e9. En caract\u00e9risant la r\u00e9ponse comportementale aux substrats G5 et G2, il sera possible d\u2019identifier les g\u00e8nes responsables de la r\u00e9ponse ou de la non-r\u00e9ponse \u00e0 G5.  Pour mener \u00e0 bien ce projet, l\u2019\u00e9tudiant(e) utilisera un dispositif d\u00e9velopp\u00e9 au laboratoire de mesure de la consommation de mouches, le multiCaFe (multi-capillary feeding) qui nous permet de suivre les choix alimentaires d\u2019une centaine d\u2019individus de mani\u00e8re semi-automatis\u00e9e. Ensuite, par analyse GWAS (genome-wide association study), en contrastant les lign\u00e9es les plus sensibles et les moins sensibles au G5, on sera \u00e0 m\u00eame de rep\u00e9rer des g\u00e8nes potentiellement impliqu\u00e9s dans la sensibilit\u00e9 sensorielle \u00e0 cet oligom\u00e8re du glucose. Une fois des g\u00e8nes candidats identifi\u00e9s, leur r\u00f4le dans la d\u00e9tection de G5 sera confirm\u00e9 ou infirm\u00e9 par une analyse g\u00e9n\u00e9tique consistant \u00e0 activer\/inactiver ces g\u00e8nes chez des mouches t\u00e9moin.<\/p>\n\n\n\n

Genetic analysis of oligosaccharide detection in Drosophila melanogaster<\/p>\n\n\n\n

Drosophilas feed on microorganisms such as yeasts, that thrive on decaying fruits, but they also eat various nutrients from these fruits, such as carbohydrates, that they appreciate. They are able to digest starch thanks to an enzyme, alpha-amylase, but they cannot sense starch itself. Their sensory system is known to enable Drosophila melanogaster to detect monomeric sugars like glucose or fructose, or dimers like maltose or saccharose using 9 gustatory receptors (GR)  over 60 that are present.<\/p>\n\n\n\n

We have carried out a series of behavior and electrophysiology observations to assess the capacity of detecting glucose polymers (up to G12) in D. melanogaster adults. While we were expecting the highest sensitivity for glucose and maltose and then a progressive decrease with increasing polymer length, we observed that sensitivity increased up to G5, then decreased from G6 to G12. This result cannot be easily interpreted, peculiarly regarding the detection mechanism. Such a detection would require that the flies be endowed with GRs harboring a detection site of sufficient size to accomodate a bulky molecule such as maltopentaose, or a cooperation between neighboring receptors, or the quick action of an enzyme degrading the glucose polymers into smaller sugars inside gustatory sensillas.<\/p>\n\n\n\n

In order to decipher the mechanisms at work, we propose a genomic approach based on the study of the extant variability of a drosophila population. This takes advantage of the Drosophila genetic reference panel (DGRP), a collection of 200 iso-female lines from a single american population collected on a market, each of which with its genome sequenced. Characterizing the behavioral response to G5 vs. G2, we will assign lines into responsive or non-responsive to G5.<\/p>\n\n\n\n

To carry out this projet, the student will make use a device set up in the laboratory, named MultiCaFe (multiple capillary feeding), that measures the individual consumption of food and food preference choice for nearly 100 flies simultaneously in a semi-automated way.<\/p>\n\n\n\n

Then, by a GWAS (genome-wide association study) analysis, contrasting the most responsive vs. the less responsive lines towards G5, we will be able to identify genes potentially involved in the sensitivity to this glucose oligomere. Once some candidate genes will be identified, their role in G5 detection will be assessed using a genetic analysis that consists in inactivationg the said genes in control flies.<\/p>\n","protected":false},"excerpt":{"rendered":"

Analyse g\u00e9n\u00e9tique de la d\u00e9tection des oligosaccharides chez Drosophila melanogaster Les drosophiles se nourrissent de microorganismes comme les levures, qu\u2019elles trouvent sur les fruits pourrissants, mais aussi des divers nutriments issus de ces fruits, comme les glucides, qu\u2019elles appr\u00e9cient. Elles sont capables de dig\u00e9rer l\u2019amidon, gr\u00e2ce \u00e0 une enzyme, l\u2019alpha-amylase, mais elles ne per\u00e7oivent pas […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"_themeisle_gutenberg_block_has_review":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-16982","post","type-post","status-publish","format-standard","hentry","category-non-classe"],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.egce.universite-paris-saclay.fr\/index.php?rest_route=\/wp\/v2\/posts\/16982","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.egce.universite-paris-saclay.fr\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.egce.universite-paris-saclay.fr\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.egce.universite-paris-saclay.fr\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.egce.universite-paris-saclay.fr\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=16982"}],"version-history":[{"count":1,"href":"https:\/\/www.egce.universite-paris-saclay.fr\/index.php?rest_route=\/wp\/v2\/posts\/16982\/revisions"}],"predecessor-version":[{"id":16983,"href":"https:\/\/www.egce.universite-paris-saclay.fr\/index.php?rest_route=\/wp\/v2\/posts\/16982\/revisions\/16983"}],"wp:attachment":[{"href":"https:\/\/www.egce.universite-paris-saclay.fr\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=16982"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.egce.universite-paris-saclay.fr\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=16982"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.egce.universite-paris-saclay.fr\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=16982"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}