Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Evolution involves interplay between natural selection and developmental constraints(1-3). This is seen, for example, when digits are lost from the limbs during evolution(1,3,4). Extant archosaurs (crocodiles and birds) show several instances of digit loss(3,5,6) under different selective regimes, and show limbs with one, two, three, four or the ancestral number of five digits. The `lost' digits sometimes persist for millions of years as developmental vestiges(7-10). Here we examine digit loss in the Nile crocodile and five birds, using markers of three successive stages of digit development. In two independent lineages under different selection, wing digit I and all its markers disappear. In contrast, hindlimb digit V persists in all species sampled, both as cartilage, and as Sox9-expressing precartilage domains, 250 million years after the adult digit disappeared. There is therefore a mismatch between evolution of the embryonic and adult phenotypes. All limbs, regardless of digit number, showed similar expression of sonic hedgehog (Shh). Even in the one-fingered emu wing, expression of posterior genes Hoxd11 and Hoxd12 was conserved, whereas expression of anterior genes Gli3 and Alx4 was not. We suggest that the persistence of digit V in the embryo may reflect constraints, particularly the conserved posterior gene networks associated with the zone of polarizing activity (ZPA(11)). The more rapid and complete disappearance of digit I may reflect its ZPA-independent specification, and hence, weaker developmental constraints. Interacting with these constraints are selection pressures for limb functions such as flying and perching. This model may help to explain the diverse patterns of digit loss in tetrapods. Our study may also help to understand how selection on adults leads to changes in development.
ISSN: 0028-0836

hal-01545485
https://hal.archives-ouvertes.fr/hal-01545485
DOI : 10.1038/nature12336

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
The formation of ovarian follicles is a finely tuned process that takes place within a narrow time-window in rodents. Multiple factors and pathways have been proposed to contribute to the mechanisms triggering this process but the role of endocrine factors, especially estrogens, remains elusive. It is currently hypothesized that removal from the maternal hormonal environment permits follicle formation at birth. However, experimentally-induced maintenance of high 17β-estradiol (E2) levels leads to subtle, distinct, immediate effects on follicle formation and oocyte survival depending on the species and dose. In this study, we examined the immediate effects of neonatal E2 exposure from post-natal day (PND) 0 to PND2 on the whole organism and on ovarian follicle formation in rats. Measurements of plasma E2, estrone and their sulfate conjugates after E2 exposure showed that neonatal female rats rapidly acquire the capability to metabolize and clear excessive E2 levels. Concomitant modifications to the mRNA content of genes encoding selected E2 metabolism enzymes in the liver and the ovary in response to E2 exposure indicate that E2 may modify the neonatal maturation of these organs. In the liver, E2 treatment was associated with lower acquisition of the capability to metabolize E2. In the ovary, E2 depleted the oocyte pool in a dose dependent manner by PND3. In 10 µg/day E2-treated ovaries, apoptotic oocytes were observed in newly formed follicles in addition to areas of ovarian cord remodeling. At PND6, follicles without any visible oocyte were present and multi-oocyte follicles were not observed. Our study reveals a major species-difference. Indeed, neonatal exposure to E2 depletes the oocyte pool in the rat ovary, whereas in the mouse it is well known to increase oocyte survival.
ISSN: 1932-6203

hal-00936582
https://hal-univ-rennes1.archives-ouvertes.fr/hal-00936582
https://hal-univ-rennes1.archives-ouvertes.fr/hal-00936582/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-00936582/file/Systemic_Compensatory_Response-accepted.pdf
DOI : 10.1371/journal.pone.0082175

Éditeur(s) : EUTIC : le réseau international et interdisciplinaire pour les Enjeux et Usages des Technologies de l'Information et de la Communication
Extrait de : "Les écosystèmes numériques et la démocratisation informationnelle" : colloque, les 3 et 4 novembre 2015. Université des Antilles
Description : L'utilisation des réseaux de communication et particulièrement d'Internet fait désormais partie de l'environnement fonctionnel et intellectuel de notre société. Les technologies de l'information et de la communication (TIC) instaurent de nouvelles articulations entre les processus de production de diffusion et de réception de l'information et de la connaissance. Dans cette communication, Lise VIERIA, professeur de l'université Bordeaux Montaigne, propose d?explorer la genèse des logiques de mise en réseau des activités et des productions intellectuelles humaines. C'est un des paradoxes de notre temps que de voir cohabiter deux logiques (de type hiérarchique et de type réticulé), apparemment contradictoires. En effet, entre la pyramide et le réseau, une évolution paradigmatique fondamentale se trouve mise en lumière par le développement sans cesse croissant des technologies numériques.
Siècle(s) traité(s) : 21
Droits : CC-BY-NC-ND - Attribution - Pas d'utilisation commerciale - Pas de modification
Permalien : http://www.manioc.org/fichiers/V15390
V15390

Résumé : Les variétés modernes de canne à sucre sont d'origine bispécifique et possèdent une structure génétique complexe, aneuploïde et hautement polyploïde rendant difficile les études de résistance génétique. La feuille jaune de la canne a sucre est une maladie dont l'agent causal est le sugarcane yellow leaf virus (scylv). Ce virus a une large diversité. Seuls trois génotypes viraux, différenciables par rtpcr, ont été trouves en Guadeloupe. Les objectifs de l'étude sont d'évaluer: l/la possibilité de marquer la résistance de la plante au scylv grâce a une étude d'association pan-génomique 2/l'impact de la diversité de l'agent pathogène sur la résistance de la canne a sucre au scylv. Les études d'association ont été menées avec plus de 4000 marqueurs aflp et d'art sur quatre types de données phénotypiques (intensité et densité virale dans les feuilles et les tiges). Les phénotypes ont été mesures sur 189 variétés de cannes à sucre dans deux essais successifs dans un dispositif en trois blocs randomises. De ces variétés, 40 ont été sélectionnées et ont permis d'obtenir 10 croisements biparentaux. Les descendances obtenues ont été suivies sur deux essais. L'incidence et la diversité du scylv ont été évaluées pour les 40 variétés et les descendances. L'héritabilité au sens strict de la résistance aux scylv a été déterminée. Six marqueurs de résistance au scylv ont été identifies ainsi que deux gènes ayant potentiellement un rôle dans la résistance au virus. L'étude montre également que la résistance de la plante est variable en fonction du génotype du scylv et que cette résistance est en partie transmise aux descendances. Créer des variétés résistantes au scylv est donc possible.
Modern varieties of sugarcane have a bispecific origin and a complex genetic structure, aneuploid and highly polyploid, maklng genetic resistance study uneasy to perform. Yellow leaf of sugarcane is a viral disease whose causal agent is the sugarcane yellow leaf virus (scylv). This virus has a wide range of diversity. Only three viral genotypes, distinguishable by rt-pcr, were found in guadeloupe. The objectives of this srudy are to assess: l/the possibility to find markers associated with plant resistance to scylv through a genome wide association study 2 1 the impact of the pathogen diversity on the resistance of sugarcane to scylv. Association studies have been conducted with more than 4000 aflp and dart markers on four types of phenotypic data (virus intensity and density in leaves and canes). Phenotypes were measured on 189 varieties of sugarcane in two successive trials in a three randomized complete block design. From these varieties, 40 were selected and allowed to obtain 10 biparental crosses. The offspring were followed during two trials. The incidence and the diversity of scylv were evaluated in the 40 varieties and the offspring. The narrow sense heritability of the resistance to the scylvs was determined. Six markers of the resistance to the scylv and two genes, with potential contribution in virus resistance, have been identified. The study also shows that the resistance of the plant is variable depending on the scylv genotype and that this resistance is partly transmitted to the offspring. Breeding for scylv resistance is practicable.

http://www.theses.fr/2012AGUY0554/document

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
Defining homologous genes is important in many evolutionary studies but raises obvious issues. Some of these issues are conceptual and stem from our assumptions of how a gene evolves, others are practical, and depend on the algorithmic decisions implemented in existing software. Therefore, to make progress in the study of homology, both ontological and epistemological questions must be considered. In particular, defining homologous genes cannot be solely addressed under the classic assumptions of strong tree thinking, according to which genes evolve in a strictly tree-like fashion of vertical descent and divergence and the problems of homology detection are primarily methodological. Gene homology could also be considered under a different perspective where genes evolve as ``public goods,'' subjected to various introgressive processes. In this latter case, defining homologous genes becomes a matter of designing models suited to the actual complexity of the data and how such complexity arises, rather than trying to fit genetic data to some a priori tree-like evolutionary model, a practice that inevitably results in the loss of much information. Here we show how important aspects of the problems raised by homology detection methods can be overcome when even more fundamental roots of these problems are addressed by analyzing public goods thinking evolutionary processes through which genes have frequently originated. This kind of thinking acknowledges distinct types of homologs, characterized by distinct patterns, in phylogenetic and nonphylogenetic unrooted or multirooted networks. In addition, we define `` family resemblances'' to include genes that are related through intermediate relatives, thereby placing notions of homology in the broader context of evolutionary relationships. We conclude by presenting some payoffs of adopting such a pluralistic account of homology and family relationship, which expands the scope of evolutionary analyses beyond the traditional, yet relatively narrow focus allowed by a strong tree-thinking view on gene evolution.
ISSN: 0737-4038

hal-01544794
https://hal.archives-ouvertes.fr/hal-01544794
DOI : 10.1093/molbev/mst228

Éditeur(s) : Springer
Résumé : The transforming growth factor (TGF)-beta superfamily is a group of important growth factors involved in multiple processes such as differentiation, cell proliferation, apoptosis and cellular growth. In the Pacific oyster Crassostrea gigas, the oyster gonadal (og) TGF-beta gene was recently characterized through genome-wide expression profiling of oyster lines selected to be resistant or susceptible to summer mortality. Og TGF-beta appeared specifically expressed in the gonad to reach a maximum when gonads are fully mature, which singularly contrasts with the pleiotropic roles commonly ascribed to most TGF-beta family members. The function of og TGF-beta protein in oysters is unknown, and defining its role remains challenging. In this study, we develop a rapid bacterial production system to obtain recombinant og TGF-beta protein, and we demonstrate that og TGF-beta is processed by furin to a mature form of the protein. This mature form can be detected in vivo in the gonad. Functional inhibition of mature og TGF-beta in the gonad was conducted by inactivation of the protein using injection of antibodies. We show that inhibition of og TGF-beta function tends to reduce gonadic area. We conclude that mature og TGF-beta probably functions as an activator of germ cells development in oyster.
Marine Biotechnology (1436-2228) (Springer), 2011-10 , Vol. 13 , N. 5 , P. 971-980

Droits : Springer Science+Business Media, LLC 2011
http://archimer.ifremer.fr/doc/00042/15371/13438.pdf
DOI:10.1007/s10126-010-9361-4
http://archimer.ifremer.fr/doc/00042/15371/

Éditeur(s) : HAL CCSD BioMed Central
Résumé : International audience
Background : In a recent study, we have demonstrated that amelotin (AMTN) gene structure and its expression during amelogenesis have changed during tetrapod evolution. Indeed, this gene is expressed throughout enamel matrix deposition and maturation in non-mammalian tetrapods, while in mammals its expression is restricted to the transition and maturation stages of amelogenesis. Previous studies of amelogenin (AMEL) gene expression in a lizard and a salamander have shown similar expression pattern to that in mammals, but to our knowledge there are no data regarding ameloblastin (AMBN) and enamelin (ENAM) expression in non-mammalian tetrapods. The present study aims to look at, and compare, the structure and expression of four enamel matrix protein genes, AMEL, AMBN, ENAM and AMTN during amelogenesis in the lizard Anolis carolinensis.Results : We provide the full-length cDNA sequence of A. carolinensis AMEL and AMBN, and show for the first time the expression of ENAM and AMBN in a non-mammalian species. During amelogenesis in A. carolinensis, AMEL, AMBN and ENAM expression in ameloblasts is similar to that described in mammals. It is noteworthy that AMEL and AMBN expression is also found in odontoblasts. Conclusions : Our findings indicate that AMTN is the only enamel matrix protein gene that is differentially expressed in ameloblasts between mammals and sauropsids. Changes in AMTN structure and expression could be the key to explain the structural differences between mammalian and reptilian enamel, i.e. prismatic versus non-prismatic.
ISSN: 2041-9139

Droits : http://creativecommons.org/licenses/by/
hal-01206550
http://hal.upmc.fr/hal-01206550
http://hal.upmc.fr/hal-01206550/document
http://hal.upmc.fr/hal-01206550/file/Gasse_2015_Comparative.pdf
DOI : 10.1186/s13227-015-0024-4

Éditeur(s) : HAL CCSD BioMed Central
Résumé : [b]Background[/b][br/] [br/] The Amazonian rainforest is predicted to suffer from ongoing environmental changes. Despite the need to evaluate the impact of such changes on tree genetic diversity, we almost entirely lack genomic resources.[br/] [br/] [b]Results[/b][br/] [br/] In this study, we analysed the transcriptome of four tropical tree species (Carapa guianensis, Eperua falcata, Symphonia globulifera and Virola michelii) with contrasting ecological features, belonging to four widespread botanical families (respectively Meliaceae, Fabaceae, Clusiaceae and Myristicaceae). We sequenced cDNA libraries from three organs (leaves, stems, and roots) using 454 pyrosequencing. We have developed an R and bioperl-based bioinformatic procedure for de novo assembly, gene functional annotation and marker discovery. Mismatch identification takes into account single-base quality values as well as the likelihood of false variants as a function of contig depth and number of sequenced chromosomes. Between 17103 (for Symphonia globulifera) and 23390 (for Eperua falcata) contigs were assembled. Organs varied in the numbers of unigenes they apparently express, with higher number in roots. Patterns of gene expression were similar across species, with metabolism of aromatic compounds standing out as an overrepresented gene function. Transcripts corresponding to several gene functions were found to be over- or underrepresented in each organ. We identified between 4434 (for Symphonia globulifera) and 9076 (for Virola surinamensis) well-supported mismatches. The resulting overall mismatch density was comprised between 0.89 (S. globulifera) and 1.05 (V. surinamensis) mismatches/100 bp in variation-containing contigs.[br/] [br/] [b]Conclusion[/b][br/] [br/] The relative representation of gene functions in the four transcriptomes suggests that secondary metabolism may be particularly important in tropical trees. The differential representation of transcripts among tissues suggests differential gene expression, which opens the way to functional studies in these non-model, ecologically important species. We found substantial amounts of mismatches in the four species. These newly identified putative variants are a first step towards acquiring much needed genomic resources for tropical tree species.
ISSN: 1471-2164

hal-01032439
https://hal.archives-ouvertes.fr/hal-01032439
https://hal.archives-ouvertes.fr/hal-01032439/document
https://hal.archives-ouvertes.fr/hal-01032439/file/art_10-1186_1471-2164-15-238.pdf
DOI : 10.1186/1471-2164-15-238

Éditeur(s) : Academic Press Ltd- Elsevier Science Ltd
Résumé : The understanding of reciprocal interactions between Crassostrea gigas and Vibrio sp., whether these be virulent or avirulent, is vital for the development of methods to improve the health status of cultured oysters. We describe an original non-invasive experimental infection technique using cohabitation, designed to explore these interactions. Using real-time PCR techniques we examined the dynamics of virulent and avirulent Vibrio sp. in oyster hemolymph and tank seawater, and made a parallel study of the expression of four genes involved in oyster immune defense: Cg-BPI, Cg-EcSOD, Cg-IκB, Cg-TIMP. No mortality occurred in control animals, but oysters put in cohabitation for 2–48 h with animals previously infected by two Vibrio pathogens suffered mortalities from 2 to 16 days post-cohabitation. Our results show that virulent Vibrio infect healthy individuals after only 2 h of cohabitation, with values ranging from 4.5×102 to 2×104 cells ml−1 hemolymph. Simultaneously, an approximate ten-fold increase of the total Vibrio population was observed in control animals, with a 6.6–78.5-fold up-expression of targeted genes. In contrast, oysters exposed to harmful bacteria had mean expression levels strongly down-regulated by a factor of 9.2–29 (depending on the gene) compared with control animals. Although oysters were still found to be infected by virulent Vibrio after 6–48 h of cohabitation, no significant differences were noted when comparing levels of each transcript in control and infected oysters at the same sampling times during this period: the important differences were noted before 6 h cohabitation. Taken together, our data support (1) the hypothesis that virulent Vibrio disturbs the immune response of this invertebrate host both rapidly and significantly, although this occurs specifically during an early and transient period during the first 6 h of cohabitation challenge, and that (2) expression of targeted genes is not correlated with vibriosis resistance.
Fish & Shellfish Immunology (1050-4648) (Academic Press Ltd- Elsevier Science Ltd), 2011-02 , Vol. 30 , N. 2 , P. 691-699

Droits : 2011 Elsevier Ltd All rights reserved.
http://archimer.ifremer.fr/doc/00025/13604/10681.pdf
DOI:10.1016/j.fsi.2010.12.017
http://archimer.ifremer.fr/doc/00025/13604/

Éditeur(s) : Taylor & Francis Ltd
Résumé : A new benthic phototrophic dinoflagellate is described from sediments of a tropical marine cove at Martinique Island and its micromorphology is studied by means of light and electron microscopy. The cell contains small golden-brown chloroplasts and the oval nucleus is posterior. It is laterally compressed, almost circular in shape when viewed laterally. It consists of a small epitheca tilted toward the right lateral side and a larger hypotheca. In the left view, the cingulum is more anterior and the epitheca is reduced. The cingulum is displaced and left-handed. This organism is peculiar in having no apical pore and its thecal plate arrangement is 2 ' 1a 7 '' 5c 3s 5 ''' 1 ''''. The plates are smooth with small groups of pores scattered on their surface. An area with 60-80 densely arranged pores is found near the centre of the 2 ''' plate, on the left lateral side. Morphologically, these features are different from all other laterally compressed benthic genera. In addition, molecular genetic sequences of SSU and partial LSU form a distinct and well-supported clade among dinoflagellates and support the erection of a new genus. However, molecular phylogenies inferred from ribosomal genes failed to confirm any clear relationship with other benthic taxa and affinity with other laterally compressed dinoflagellates has not been demonstrated. Hence, the taxonomic affinity of Madanidinium loirii with a defined order and family is unclear at the moment.
European Journal Of Phycology (0967-0262) (Taylor & Francis Ltd), 2014-04 , Vol. 49 , N. 2 , P. 165-178

Droits : 2014 British Phycological Society
http://archimer.ifremer.fr/doc/00195/30622/29458.pdf
DOI:10.1080/09670262.2014.898797
http://archimer.ifremer.fr/doc/00195/30622/

Éditeur(s) : HAL CCSD BioMed Central
Résumé : International audience
BACKGROUND: Environmental factors such as pesticides can cause phenotypic changes in various organisms, including mammals. We studied the effects of the widely used herbicide atrazine (ATZ) on meiosis, a key step of gametogenesis, in male mice. METHODS: Gene expression pattern was analysed by Gene-Chip array. Genome-wide mapping of H3K4me3 marks distribution was done by ChIP-sequencing of testis tissue using Illumina technologies. RT-qPCR was used to validate differentially expressed genes or differential peaks. RESULTS: We demonstrate that exposure to ATZ reduces testosterone levels and the number of spermatozoa in the epididymis and delays meiosis. Using Gene-Chip and ChIP-Seq analysis of H3K4me3 marks, we found that a broad range of cellular functions, including GTPase activity, mitochondrial function and steroid-hormone metabolism, are affected by ATZ. Furthermore, treated mice display enriched histone H3K4me3 marks in regions of strong recombination (double-strand break sites), within very large genes and reduced marks in the pseudoautosomal region of X chromosome. CONCLUSIONS: Our data demonstrate that atrazine exposure interferes with normal meiosis, which affects spermatozoa production
ISSN: 1471-2164

hal-01225493
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01225493
DOI : 10.1186/s12864-015-2095-y
PUBMED : 26518232

Éditeur(s) : HAL CCSD
Résumé : International audience
Background: We examined the association between exposure during pregnancy to trihalomethanes, the most common water disinfection by-products, and birth outcomes in a European cohort study (Health Impacts of Long-Term Exposure to Disinfection By-Products in Drinking Water). We took into account exposure through different water uses, measures of water toxicity, and genetic susceptibility. Methods: We enrolled 14,005 mothers (2002-2010) and their children from France, Greece, Lithuania, Spain, and the UK. Information on lifestyle- and water-related activities was recorded. We ascertained residential concentrations of trihalomethanes through regulatory records and ad hoc sampling campaigns and estimated route-specific trihalomethane uptake by trimester and for whole pregnancy. We examined single nucleotide polymorphisms and copy number variants in disinfection by-product metabolizing genes in nested case-control studies. Results: Average levels of trihalomethanes ranged from around 10 μg/L to above the regulatory limits in the EU of 100 μg/L between centers. There was no association between birth weight and total trihalomethane exposure during pregnancy (β = 2.2 g in birth weight per 10 μg/L of trihalomethane, 95% confidence interval = 3.3, 7.6). Birth weight was not associated with exposure through different routes or with specific trihalomethane species. Exposure to trihalomethanes was not associated with low birth weight (odds ratio [OR] per 10 μg/L = 1.02, 95% confidence interval = 0.95, 1.10), small-for-gestational age (OR = 0.99, 0.94, 1.03) and preterm births (OR = 0.98, 0.9, 1.05). We found no gene-environment interactions for mother or child polymorphisms in relation to preterm birth or small-for-gestational age. Conclusions: In this large European study, we found no association between birth outcomes and trihalomethane exposures during pregnancy in the total population or in potentially genetically susceptible subgroups. © 2016 Wolters Kluwer Health, Inc.
Epidemiology

hal-01392115
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01392115
DOI : 10.1097/EDE.0000000000000544
PUBMED : 27468006

Éditeur(s) : Wiley-blackwell Publishing, Inc
Résumé : Vibrio splendidus, strain LGP32, is an oyster pathogen associated with the summer mortalities affecting the production of Crassostrea gigas oysters worldwide. Vibrio splendidus LGP32 was shown to resist to up to 10 mu M Cg-Def defensin and Cg-BPI bactericidal permeability increasing protein, two antimicrobial peptides/proteins (AMPs) involved in C. gigas immunity. The resistance to both oyster Cg-Def and Cg-BPI and standard AMPs (polymyxin B, protegrin, human BPI) was dependent on the ompU gene. Indeed, upon ompU inactivation, minimal bactericidal concentrations decreased by up to fourfold. AMP resistance was restored upon ectopic expression of ompU. The susceptibility of bacterial membranes to AMP-induced damages was independent of the ompU-mediated AMP resistance. Besides its role in AMP resistance, ompU proved to be essential for the adherence of V. splendidus LGP32 to fibronectin. Interestingly, in vivo, ompU was identified as a major determinant of V. spiendidus pathogenicity in oyster experimental infections. Indeed, the V. splendidus-induced oyster mortalities dropped from 56% to 11% upon ompU mutation (Kaplan Meier survival curves, P < 0.01). Moreover, in co-infection assays, the ompU mutant was out competed by the wild-type strain with competitive indexes in the range of 0.1-0.2. From this study, ompU is required for virulence of V. splendidus. Contributing to AMP resistance, conferring adhesive properties to V. splendidus, and being essential for in vivo fitness, the OmpU porin appears as an essential effector of the C. gigas/V. splendidus interaction.
Environmental Microbiology (1462-2912) (Wiley-blackwell Publishing, Inc), 2010-04 , Vol. 12 , N. 4 , P. 951-963

Droits : 2010 Society for Applied Microbiology and Blackwell Publishing Ltd
http://archimer.ifremer.fr/doc/00003/11421/8044.pdf
DOI:10.1111/j.1462-2920.2009.02138.x
http://archimer.ifremer.fr/doc/00003/11421/

Éditeur(s) : HAL CCSD BioMed Central
Résumé : International audience
Background: Myosin II (or Myosin Heavy Chain II, MHCII) is a family of molecular motors involved in the contractile activity of animal muscle cells but also in various other cellular processes in non-muscle cells. Previous phylogenetic analyses of bilaterian MHCII genes identified two main clades associated respectively with smooth/non-muscle cells (MHCIIa) and striated muscle cells (MHCIIb). Muscle cells are generally thought to have originated only once in ancient animal history, and decisive insights about their early evolution are expected to come from expression studies of Myosin II genes in the two non-bilaterian phyla that possess muscles, the Cnidaria and Ctenophora. Results: We have uncovered three MHCII paralogues in the ctenophore species Pleurobrachia pileus. Phylogenetic analyses indicate that the MHCIIa /MHCIIb duplication is more ancient than the divergence between extant metazoan lineages. The ctenophore MHCIIa gene (PpiMHCIIa) has an expression pattern akin to that of ``stem cell markers'' (Piwi, Vasa...) and is expressed in proliferating cells. We identified two MHCIIb genes that originated from a ctenophore-specific duplication. PpiMHCIIb1 represents the exclusively muscular form of myosin II in ctenophore, while PpiMHCIIb2 is expressed in non-muscle cells of various types. In parallel, our phalloidin staining and TEM observations highlight the structural complexity of ctenophore musculature and emphasize the experimental interest of the ctenophore tentacle root, in which myogenesis is spatially ordered and strikingly similar to striated muscle formation in vertebrates. Conclusion: MHCIIa expression in putative stem cells/proliferating cells probably represents an ancestral trait, while specific involvement of some MHCIIa genes in smooth muscle fibres is a uniquely derived feature of the vertebrates. That one ctenophore MHCIIb paralogue (PpiMHCIIb2) has retained MHCIIa-like expression features furthermore suggests that muscular expression of the other paralogue, PpiMHCIIb1, was the result of neofunctionalisation within the ctenophore lineage, making independent origin of ctenophore muscle cells a likely option.
ISSN: 1471-2148

hal-01544486
https://hal.archives-ouvertes.fr/hal-01544486
DOI : 10.1186/1471-2148-12-107

Éditeur(s) : HAL CCSD Wiley
Résumé : The extent of gene dispersal is a fundamental factor of the population and evolutionary dynamics of tropical tree species, but directly monitoring seed and pollen movement is a difficult task. However, indirect estimates of historical gene dispersal can be obtained from the fine-scale spatial genetic structure of populations at drift-dispersal equilibrium. Using an approach that is based on the slope of the regression of pairwise kinship coefficients on spatial distance and estimates of the effective population density, we compare indirect gene dispersal estimates of sympatric populations of 10 tropical tree species. We re-analysed 26 data sets consisting of mapped allozyme, SSR (simple sequence repeat), RAPD (random amplified polymorphic DNA) or AFLP (amplified fragment length polymorphism) genotypes from two rainforest sites in French Guiana. Gene dispersal estimates were obtained for at least one marker in each species, although the estimation procedure failed under insufficient marker polymorphism, limited sample size, or inappropriate sampling area. Estimates generally suffered low precision and were affected by assumptions regarding the effective population density. Averaging estimates over data sets, the extent of gene dispersal ranged from 150 m to 1200 m according to species. Smaller gene dispersal estimates were obtained in species with heavy diaspores, which are presumably not well dispersed, and in populations with high local adult density. We suggest that limited seed dispersal could indirectly limit effective pollen dispersal by creating higher local tree densities, thereby increasing the positive correlation between pollen and seed dispersal distances. We discuss the potential and limitations of our indirect estimation procedure and suggest guidelines for future studies
ISSN: 0962-1083

hal-01031603
https://hal.archives-ouvertes.fr/hal-01031603
DOI : 10.1111/j.1365-294X.2005.02785.x

Éditeur(s) : HAL CCSD American Society for Microbiology
Résumé : International audience
This study aimed to evaluate the repeated sequence REP-529 compared to the B1 gene for the molecular diagnosis of toxoplasmosis by quantitative PCR (qPCR) in routine diagnosis.Over a ten-year period (2003-2013), all patients prospectively diagnosed with a positive REP-529 qPCR result for toxoplasmosis were included. All DNA samples (76 samples from 56 patients) were simultaneously tested using the two qPCR methods (REP-529 and B1).The mean Ct obtained with the B1 qPCR was significantly higher (+4.71 cycles) than that obtained with REP-529 qPCR (p<0.0001). Thirty-one out of 69 extracts (45.6%) positive with REP-529 qPCR were not amplified with the B1 qPCR (relative sensitivity 54.4%, compared to REP-529), yielding false negative results on 15/28 placentas, 5 cord blood, 2 amniotic fluids, 4 cerebrospinal fluids, 1 aqueous humor, 2 lymph node punctures and 1 abortion product. This defect in sensitivity would have left 20/56 patients undiagnosed, distributed as follows: 12/40 congenital toxoplasmosis, 4/5 cerebral toxoplasmosis, 2/8 patients with retinochoroiditis, and both patients with chronic lymphadenopathy. This poor performance of B1 qPCR could be related to low parasite loads, since the mean Toxoplasma quantification in extracts with B1 false negative results was 0.4 parasite/reaction.These results clearly show the superiority of the REP-529 sequence in the diagnosis of toxoplasmosis by PCR suggest that this target should be adopted as part of standardization of the PCR assay.
ISSN: 0095-1137

hal-01118293
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01118293
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01118293/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01118293/file/A%2010-Year%20Retrospective%20Comparison%20of%20Two%20Target%20Sequences-belaz2015.pdf
PUBMEDCENTRAL : PMC4365238

Éditeur(s) : HAL CCSD Frontiers Media
Résumé : "Candidatus Liberibacter solanacearum" (Lso) has emerged as a serious threat world-wide. Five Lso haplotypes have been identified so far. Haplotypes A and B are present in the Americas and/or New Zealand, where they are vectored to solanaceous plants by the potato psyllid, Bactericera cockerelli (Sulc) (Hemiptera: Triozidae). The fastidious nature of these pathogens has hindered the study of the interactions with their eukaryotic hosts (vector and plant). To understand the strategies used by these pathogens to infect their vector, the effects of each Lso haplotype (A or B) on psyllid fitness was investigated, and genome-wide transcriptomic and RT-qPCR analyses were performed to evaluate Lso gene expression in association with its vector. Results showed that psyllids infected with haplotype B had significantly lower percentage of nymphal survival compared to psyllids infected with haplotype A. Although overall gene expression across Lso genome was similar between the two Lso haplotypes, differences in the expression of key candidate genes were found. Among the 16 putative type IV effector genes tested, four of them were differentially expressed between Lso haplotypes, while no differences in gene expression were measured by qPCR or transcriptomic analysis for the rest of the genes. This study provides new information regarding the pathogenesis of Lso haplotypes in their insect vector.
ISSN: 2235-2988

hal-01512244
https://hal.archives-ouvertes.fr/hal-01512244
https://hal.archives-ouvertes.fr/hal-01512244/document
https://hal.archives-ouvertes.fr/hal-01512244/file/Yao%202016%20Frontiers%20in%20Cellular%20and%20Infection%20Microbiology_%7BD6ACF6EB-9794-4F27-AB84-9EF4099B6D78%7D.pdf
DOI : 10.3389/fcimb.2016.00062

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Predictive toxicology aims at developing methodologies to relate the results obtained from in vitro experiments to in vivo exposure. In the case of polycyclic aromatic hydrocarbons (PAHs), a substantial amount of knowledge on effects and modes of action has been recently obtained from in vitro studies of gene expression. In the current study, we built a physiologically based toxicokinetic (PBTK) model to relate in vivo and in vitro gene expression in case of exposure to benzo(a)pyrene (BaP), a referent PAH. This model was calibrated with two toxicokinetic datasets obtained on rats exposed either through intratracheal instillation or through intravenous administration and on an in vitro degradation study. A good agreement was obtained between the model's predictions and the concentrations measured in target organs, such as liver and lungs. Our model was able to relate correctly the gene expression for two genes targeted by PAHs, measured in vitro on primary human macrophages and in vivo in rat macrophages after exposure to BaP. Combining in vitro studies and PBTK modeling is promising for PAH risk assessment, especially for mixtures which are more efficiently studied in vitro than in vivo.
Toxicology Letters

hal-00873317
https://hal.archives-ouvertes.fr/hal-00873317
https://hal.archives-ouvertes.fr/hal-00873317/document
DOI : 10.1016/j.toxlet.2010.11.017
PUBMED : 21134426

Éditeur(s) : HAL CCSD
Résumé : The trophic endosymbiosis interaction between a cnidarian host and its photosynthetic dinoflagellatessymbionts form the basis of coral reef ecosystems. Cnidarians host their symbionts in gastrodermis cells, in a phagocytosis-derived vacuole. Establishment and maintenance of the symbiotic interaction depend on an intimate molecular communication between the two partners. However, environmental and/or anthropogenic disturbances can lead to the breakdown of the symbiotic association, which is responsible for the worldwide decline of coral reefs. The main objectives of my research project are to improve the knowledge regarding symbiosis maintenance and disruption mechanisms, but also to define the molecular key players involved at the symbiotic interface in the sea anemone, Anemonia viridis. First, we have described the cellular mechanisms involved in the different types of symbiosis breackdown. Meanwhile, the characterization of npc1 and npc2 genes (involved in endosomal sterol transport), showed a duplication and a sub-functionalization of the npc2d gene. Both NPC1 and NPC2 proteins are expressed around symbionts. We therefore suggest that the duplicated protein NPC2-d is a biomarker of symbiosis health and that NPC1 protein is a marker of the perisymbiotic membrane. We then developed a protocol to characterize the proteome of the symbiotic interface between the two symbiotic partners. The newly-identified symbiotic key players will increase the general knowledge on the symbiotic interaction and its regulation during both stable and bleaching conditions.
L’endosymbiose trophique établie entre un hôte Cnidaire et ses symbiotes Dinoflagellés photosynthétiques est à l’origine du succès évolutif des écosystèmes coralliens. Les symbiotes sont internalisés par un mécanisme de phagocytose et maintenus dans les cellules du gastroderme de l'hôte. La symbiose est régie par un dialogue moléculaire intime entre les deux partenaires, interrompu lors de perturbations environnementales ou anthropiques, responsables du déclin mondial des récifs coralliens. Les objectifs de mon projet de recherche sont de définir les acteurs moléculaires localisés à l’interface symbiotique chez l’anémone de mer, Anemonia viridis. Premièrement, nous avons étudié les mécanismes cellulaires impliqués dans différents types de rupture de la symbiose et mis en évidence des phénomènes d’apoptose, nécrose et symbiophagie. Parallèlement, nous avons caractérisé chez l’anémone les gènes npc1 et npc2, impliqués chez les vertébrés dans le transport endosomal de stérols, et dont l’expression est modulée par l’état symbiotique. Nous avons pu montrer que le gène npc2d est issus d’une duplication et vraisemblablement d’une sub-fonctionnalisation et que les protéines NPC1 et NPC2 sont exprimées au voisinage des symbiotes. Nous proposons donc que la protéine NPC2-d soit utilisée comme marqueur de l’état de santé des Anthozoaires symbiotiques et que la protéine NPC1 soit un marqueur de la membrane périsymbiotique. Nous avons également développé un protocole afin d’identifier les protéines associées à l’interface symbiotique entre les deux partenaires. A terme, les cibles identifiées permettront une meilleure compréhension des mécanismes qui régulent la relation symbiotique.
https://tel.archives-ouvertes.fr/tel-01673491

NNT : 2015NICE4105
tel-01673491
https://tel.archives-ouvertes.fr/tel-01673491
https://tel.archives-ouvertes.fr/tel-01673491/document
https://tel.archives-ouvertes.fr/tel-01673491/file/2015NICE4105.pdf

Éditeur(s) : Université Montpellier 2 - Sciences et Techniques du Languedoc
Résumé : The work reported here was motivated by the economical importance of the pacific blue shrimp Litopenaeus stylirostris farming where high mortality rates are due to bacterial and viral diseases. It consists in the characterisation of two original peptides, the first members of a new multifunctional family of peptides from peneide shrimps, the stylicines. Those two peptides, named stylicines 1 and 2, are negatively charged (pI < 6.0), and characterised by a proline-rich N-terminal region and a C-terminal region containing 13 cysteine residues. Stylicines are synthesized by heamocytes where they are stored within small cytoplasmic granules. To understand the role of these peptides in the immune response of shrimps to a vibrio infection, their recombinant forms were produced in E. coli BL21 (DE3) plysS, purified and characterised. The two rstylicines display biological anti-proliferative and blood clotting activities. Only rstylicine 1 displays antimicrobial activities: antifungal against Fusarium oxysporum (MIC<2.5μM) and bacteriostatic against Gram (−) bacteria, Vibrio sp. (MIC<80μM). Moreover this peptide displays an LPS-binding activity (dissociation constant (Kd) of 9.6×10−8 M) and agglutinate Vibrio. penaeicida "in vitro". Finally, the presence of sequences coding for modified forms of stylicine 1 in some shrimp’s genome may be in relation with their lower ability to survive infections.
Les travaux présentés dans ce mémoire ont été motivés par l’importance économique de l’élevage de la crevette bleue du pacifique Litopenaeus stylirostris dont les fortes mortalités sont principalement dues au développement de maladies bactériennes et virales. Ils ont consisté en la caractérisation des deux premiers membres d’une famille originale de peptides multifonctionnels présents chez les crevettes pénéides, les stylicines. Ces peptides, nommés stylicines 1 et 2, sont des peptides anioniques (pI < 6.0), formés d’une région amino-terminale riche en résidus de type proline et d’une région carboxyterminale riche de treize résidus cystéines. Ces molécules sont synthétisées et stockées dans de petits granules présents dans le cytoplasme des hémocytes. Pour mieux appréhender leurs rôles dans la réponse immunitaire des crevettes à une infection par des Vibrio, leurs formes recombinantes ont été produites dans E. coli BL21 (DE3) plysS, purifiées et caractérisées. Les deux rstylicines présentent des activités antiproliférative et anticoagulante. Seule la rstylicine1 présente des activités antimicrobiennes : antifongique sur Fusarium oxysporum (CMI<2.5 μM), et antibactérienne (bactériostatique) sur Vibrio sp (CMI<80 μM). Ce peptide est également capable de se lier aux LPS des bactéries à Gram (-) (Kd= 9.6x10-8 M) et d’agglutiner V. penaeicida "in vitro". Enfin, l’existence de gènes codant des formes modifiées de la stylicine1, chez certaines crevettes, pourrait être en relation avec une diminution de la résistante des individus aux infections.

Droits : 2010 The Author, Univ Montpellier 2
http://archimer.ifremer.fr/doc/00024/13558/10612.pdf
http://archimer.ifremer.fr/doc/00024/13558/