Éditeur(s) : HAL CCSD Taylor & Francis
Résumé : International audience
The origin of replication complex subunit ORC1 is important for DNA replication. The gene is known to encode a meiotic transcript isoform (mORC1) with an extended 5′-untranslated region (5′-UTR), which was predicted to inhibit protein translation. However, the regulatory mechanism that controls the mORC1 transcript isoform is unknown and no molecular biological evidence for a role of mORC1 in negatively regulating Orc1 protein during gametogenesis is available. By interpreting RNA profiling data obtained with growing and sporulating diploid cells, mitotic haploid cells, and a starving diploid control strain, we determined that mORC1 is a middle meiotic transcript isoform. Regulatory motif predictions and genetic experiments reveal that the activator Ndt80 and its middle sporulation element (MSE) target motif are required for the full induction of mORC1 and the divergently transcribed meiotic SMA2 locus. Furthermore, we find that the MSE-binding negative regulator Sum1 represses both mORC1 and SMA2 during mitotic growth. Finally, we demonstrate that an MSE deletion strain, which cannot induce mORC1, contains abnormally high Orc1 levels during post-meiotic stages of gametogenesis. Our results reveal the regulatory mechanism that controls mORC1, highlighting a novel developmental stage-specific role for the MSE element in bi-directional mORC1/SMA2 gene activation, and correlating mORC1 induction with declining Orc1 protein levels. Because eukaryotic genes frequently encode multiple transcripts possessing 5′-UTRs of variable length, our results are likely relevant for gene expression during development and disease in higher eukaryotes. © 2016 Taylor & Francis Group, LLC.
ISSN: 1547-6286

hal-01367153
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01367153
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01367153/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01367153/file/Ndt80%20activates%20the%20meiotic%20ORC1%20transcript.pdf
PUBMEDCENTRAL : PMC5013992

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
The giant bathymodioline mussels from vents have been studied as models to understand the adaptation of organisms to deep-sea chemosynthetic environments. These mussels are closely related to minute mussels associated to organic remains decaying on the deep-sea floor. Whereas biological data accumulate for the giant mussels, the small mussels remain poorly studied. Despite this lack of data for species living on organic remains it has been hypothesized that during evolution, contrary to their relatives from vents or seeps, they did not acquire highly specialized biological features. We aim at testing this hypothesis by providing new biological data for species associated with organic falls. Within Bathymodiolinae a close phylogenetic relationship was revealed between the Bathymodiolus sensu stricto lineage (i.e. ``thermophilus'' lineage) which includes exclusively vent and seep species, and a diversified lineage of small mussels, attributed to the genus Idas, that includes mostly species from organic falls. We selected Idas iwaotakii (Habe, 1958) from this latter lineage to analyse population structure and to document biological features. Mitochondrial and nuclear markers reveal a north-south genetic structure at an oceanic scale in the Western Pacific but no structure was revealed at a regional scale or as correlated with the kind of substrate or depth. The morphology of larval shells suggests substantial dispersal abilities. Nutritional features were assessed by examining bacterial diversity coupled by a microscopic analysis of the digestive tract. Molecular data demonstrated the presence of sulphur-oxidizing bacteria resembling those identified in other Bathymodiolinae. In contrast with most Bathymodiolus s.s. species the digestive tract of I. iwaotakii is not reduced. Combining data from literature with the present data shows that most of the important biological features are shared between Bathymodiolus s.s. species and its sister-lineage. However Bathymodiolus s.s. species are ecologically more restricted and also display a lower species richness than Idas species.
ISSN: 1932-6203

hal-01545914
https://hal.archives-ouvertes.fr/hal-01545914
DOI : 10.1371/journal.pone.0069680

Éditeur(s) : HAL CCSD
Résumé : Le régime de reproduction de Dicorynia guianensis (caesalpiniaceae), arbre de la forêt guyanaise a été étudié à l'aide des marqueurs enzymatiques. Le matériel végétal a été collecté en 1993 et 1995, sur le dispositif sylvicole de Paracou. Le taux d'allofécondation moyen de la population est élevé, tm = 0,85, stable d'une année à l'autre malgré une variation importante du taux de floraison. Le taux individuel varie entre les arbres mais aucune corrélation n'a pu être établie avec des facteurs spatiaux, densité de floraison ou distance aux plus proches voisins. L'hétérogénéité des nuages polliniques est sensible au niveau des agrégats et des arbres individuels, échelle spatiale où se déploie l'activité des insectes pollinisateurs. Nous n'avons en évidence aucune corrélation spatiale entre compositions des nuages polliniques individuels. Des distances de migration du pollen de 190 mètres ont été mise en évidence grâce aux allèles rares. Aucune différence significative du régime de reproduction de D. guianensis n'a été trouvée entre parcelles traitées et parcelles témoin du dispositif.
Colloque BRG/USTL. Méthodologie de gestion et de conservation des ressources génétiques
Lille, France

hal-01032382
https://hal.archives-ouvertes.fr/hal-01032382

Éditeur(s) : Springer
Résumé : Pearl oysters belonging to the genus Pinctada (Bivalvia: Pteriidae) are widely distributed between the Indo-Pacific and western Atlantic. The existence of both widely distributed and more restricted species makes this group a suitable model to study diversification patterns and prevailing modes of speciation. Phylogenies of eight out of the 11 currently recognised Pinctada species using mitochondrial (cox1) and nuclear (18S rRNA) data yielded two monophyletic groups that correspond to shell size and presence/absence of hinge teeth. Character trace of these morphological characters onto the molecular phylogeny revealed a strong correlation. Pinctada margaritifera appears polyphyletic with specimens from Mauritius grouping in a different clade from others of the French Polynesia and Japan. Hence, P. margaritifera might represent a species complex, and specimens from Mauritius could represent a different species. Regarding the putative species complex Pinctada fucata/Pinctada martensii/Pinctada radiata/Pinctada imbricata, our molecular analyses question the taxonomic validity of the morphological characters used to discriminate P. fucata and P. martensii that exhibited the lowest genetic divergence and are most likely conspecific as they clustered together. P. radiata and P. imbricata were recovered as monophyletic. The absence of overlapping distributions between sister lineages and the observed isolation by distance suggests that allopatry is the prevailing speciation mode in Pinctada. Bayesian dating analysis indicated a Miocene origin for the genus, which is consistent with the fossil record. The northward movement of the Australian plate throughout the Miocene played an important role in the diversification process within Pinctada.
Marine Biotechnology (1436-2228) (Springer), 2011-04 , Vol. 13 , N. 2 , P. 181-192

Droits : Springer Science+Business Media, LLC 2010
http://archimer.ifremer.fr/doc/00035/14635/14015.pdf
DOI:10.1007/s10126-010-9278-y
http://archimer.ifremer.fr/doc/00035/14635/

Éditeur(s) : American society for microbiology
Résumé : Vibrio nigripulchritudo, the etiological agent of Litopenaeus stylirostris summer syndrome, is responsible for mass mortalities of shrimp in New Caledonia. Epidemiological studies led to the suggestion that this disease is caused by an emergent group of pathogenic strains. Genomic subtractive hybridization was carried out between two isolates exhibiting low and high virulence. Our subtraction library was constituted of 521 specific fragments; 55 of these were detected in all virulent isolates from our collection (n = 32), and 13 were detected only in the isolates demonstrating the highest pathogenicity (n = 19), suggesting that they could be used as genetic markers for high virulence capacity. Interestingly, 10 of these markers are carried by a replicon of 11.2 kbp that contains sequences highly similar to those of a plasmid detected in Vibrio shilonii, a coral pathogen. The detection of this plasmid was correlated with the highest pathogenicity status of the isolates from our collection. The origin and consequence of this plasmid acquisition are discussed.
Applied and environmental microbiology (depuis 1953) (0099-2240) (American society for microbiology), 2008-05 , Vol. 74 , N. 10 , P. 3038-3047

Droits : 2008 American Society for Microbiology
http://archimer.ifremer.fr/doc/2008/publication-4523.pdf
DOI:10.1128/AEM.02680-07
http://archimer.ifremer.fr/doc/00000/4523/

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : Understanding the ability of ecosystem processes to resist to and to recover from disturbances is critical to sustainable land use. However, the spatial variability of the stability has rarely been addressed. Here, we investigated the functional stability of a soil microbial process for 24 soils collected from adjacent locations from a 0.3 ha tropical rainforest plot in Paracou, French Guiana. The 24 locations were characterized regarding soil chemical and biological (microbial diversity) parameters and forest structure. The corresponding soils were submitted to an experimental transient heat disturbance during a microcosm experiment. The response of the respiration process was followed using substrate-induced respiration (SIR). The response of soil SIR to heat disturbance varied widely between samples. The variability of the SIR response increased just after the disturbance, and a global rather homogeneous decrease in SIR rates was observed 15 and 30 days after. The stability of SIR in response to heat disturbance could not be related to either the genetic or the metabolic diversity of the microbial community. The initial level of SIR before the disturbance was the soil variable that best correlated with the impact of the disturbance: the soil locations with the highest initial SIR rates were the most affected 15 and 30 days after the heat disturbance. Such a heterogeneous response suggests that the response of soil processes to a disturbance will be difficult to assess from only local-scale analyses and highlights the need for spatial explicitness in understanding biogeochemical processes.
ISSN: 1439-0108

hal-01204209
https://hal.archives-ouvertes.fr/hal-01204209
DOI : 10.1007/s11368-012-0528-7
PRODINRA : 214444

Éditeur(s) : HAL CCSD Elsevier Masson
Résumé : International audience
The only symbiotic Mediterranean gorgonian, Eunicella singularis, has faced several mortality events connected to abnormal high temperatures. Since thermotolerance data remain scarce, heat-induced necrosis was monitored in aquarium by morphometric analysis. Gorgonian tips were sampled at two sites: Medes (Spain) and Riou (France) Islands, and at two depths: 15 m and-35 m. Although coming from contrasting thermal regimes, seawater above 28 degrees C led to rapid and complete tissue necrosis for all four populations. However, at 27 degrees C, the time length leading to 50% tissue necrosis allowed us to classify samples within three classes of thermal sensitivity. Irrespectively of the depth, Medes specimens were either very sensitive or resistant, while Riou fragments presented a medium sensitivity. Microsatellite analysis revealed that host and symbiont were genetically differentiated between sites, but not between depths. Finally, these genetic differentiations were not directly correlated to a specific thermal sensitivity whose molecular bases remain to be discovered.
ISSN: 1631-0691

hal-01546168
https://hal.archives-ouvertes.fr/hal-01546168
DOI : 10.1016/j.crvi.2013.06.008

Éditeur(s) : HAL CCSD BioMed Central
Résumé : International audience
Background: The meiotic developmental pathway in yeast enables both differentiation of vegetative cells into haploid spores that ensure long-term survival, and recombination of the parental DNA to create genetic diversity. Despite the importance of proper metabolic regulation for the supply of building blocks and energy, little is known about the reprogramming of central metabolic pathways in meiotically differentiating cells during passage through successive developmental stages. Results: Metabolic regulation during meiotic differentiation in budding yeast was analyzed by integrating information on genome-wide transcriptional activity, 26 enzymatic activities in the central metabolism, the dynamics of 67 metabolites, and a metabolic flux analysis at mid-stage meiosis. Analyses of mutants arresting sporulation at defined stages demonstrated that metabolic reprogramming is tightly controlled by the progression through the developmental pathway. The correlation between transcript levels and enzymatic activities in the central metabolism varies significantly in a developmental stage-dependent manner. The complete loss of phosphofructokinase activity at mid-stage meiosis enables a unique setup of the glycolytic pathway which facilitates carbon flux repartitioning into synthesis of spore wall precursors during the co-assimilation of glycogen and acetate. The need for correct homeostasis of purine nucleotides during the meiotic differentiation was demonstrated by the sporulation defect of the AMP deaminase mutant amd1, which exhibited hyper-accumulation of ATP accompanied by depletion of guanosine nucleotides. Conclusions: Our systems-level analysis shows that reprogramming of the central metabolism during the meiotic differentiation is controlled at different hierarchical levels to meet the metabolic and energetic needs at successive developmental stages.
ISSN: 1471-2180

inserm-01094132
http://www.hal.inserm.fr/inserm-01094132
http://www.hal.inserm.fr/inserm-01094132/document
http://www.hal.inserm.fr/inserm-01094132/file/s12915-014-0060-x.pdf
DOI : 10.1186/s12915-014-0060-x