UniversiteMontpellier 2

France

UniversiteMontpellier 2

France
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Melo-Ferreira J.,University of Porto | Vilela J.,University of Porto | Fonseca M.M.,University of Porto | Fonseca M.M.,University of Vigo | And 5 more authors.
Genome Biology and Evolution | Year: 2014

Mitochondria play a fundamental role in cellular metabolism, being responsible for most of the energy production of the cell in the oxidative phosphorylation (OXPHOS) pathway. Mitochondrial DNA (mtDNA) encodes for key components of this process, but its direct role in adaptationremains far from understood.Hares (Lepus spp.) are privilegedmodels tostudy the impactofnatural selection on mitogenomic evolution because 1) species are adapted to contrasting environments, including arctic, with different metabolic pressures, and 2) mtDNA introgression from arctic into temperate species is widespread. Here, we analyzed the sequences of 11 complete mitogenomes (ten newly obtained) of hares of temperate and arctic origins (including twoof arctic origin introgressed into temperate species). The analysis of patterns of codon substitutions along the reconstructed phylogeny showed evidence for positive selection in several codons in genes of theOXPHOS complexes,most notably affecting the arctic lineage. However, using theoretical models, no predictable effect of these differences was found on the structure and physicochemical properties of the encoded proteins, suggesting that the focus of selection may lie on complex interactions with nuclear encoded peptides. Also, a cloverleaf structure was detected in the control region only from the arctic mtDNA lineage, which may influence mtDNA replication and transcription. These results suggest that adaptation impacted the evolution of hare mtDNA andmay have influenced the occurrence and consequences of the many reported cases ofmassivemtDNA introgression. However, the origin of adaptation remains elusive. © The Author(s) 2014. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.


Ferreira T.,Stellenbosch University | van Reenen C.,Stellenbosch University | Pages S.,French National Institute for Agricultural Research | Pages S.,UniversiteMontpellier 2 | And 4 more authors.
International Journal of Systematic and Evolutionary Microbiology | Year: 2013

The bacterial symbiont AM7T, isolated from a novel entomopathogenic nematode species of the genus Heterorhabditis, displays the main phenotypic traits of the genus Photorhabdus and is highly pathogenic to Galleria mellonella. Phylogenetic analysis based on a multigene approach (16S rRNA,recA, gyrB, dnaN, gltX and infB) confirmed the classification of isolate AM7Twithin the species Photorhabdus luminescens and revealed its close relatedness to Photorhabdus luminescens subsp. caribbeanensis, P. luminescens subsp. akhurstii and P. luminescens subsp. hainanensis. The five concatenated protein-encoding sequences (4197 nt) of strain AM7T revealed 95.8, 95.4 and 94.9 % nucleotide identity to sequences of P. luminescenssubsp. caribbeanensis HG29T, P. luminescens subsp. akhurstii FRG04T and P. luminescens subsp. hainanensis C8404T, respectively. These identity values are less than the threshold of 97 % proposed for classification within one of the existing subspecies of P. luminescens. Unlike other strains described for P. luminescens, strain AM7T produces acid from adonitol, sorbitol and xylitol, assimilates xylitol and has no lipase activity on medium containing Tween 20 or 60. Strain AM7T is differentiated from P. luminescens subsp. caribbeanensisby the assimilation of N-acetylglucosamine and the absence of haemolytic activity. Unlike P. luminescens subsp. akhurstii, strain AM7T does not assimilate mannitol, and it is distinguished from P. luminescens subsp.hainanensis by the assimilation of trehalose and citrate, the inability to produce indole from tryptophan and the presence of acetoin production and urease activity. Strain AM7T (= ATCC BAA-2407T = DSM 25462T) belongs to a novel subspecies, and is proposed as the type strain of Photorhabdus luminescens subsp. noenieputensis sp. nov. © 2013 IUMS.


Douchin D.,Macquarie University | Douchin D.,UniversiteMontpellier 2 | De Marco O.,Macquarie University | Frew D.J.,Macquarie University | And 11 more authors.
Proceedings of the International Astronomical Union | Year: 2011

During the past 20 years, the idea that non-spherical planetary nebulae might need a binary or planetary interaction to be shaped was discussed by various authors. It is now generally agreed that the varied morphologies of planetary nebulae cannot be fully explained solely by single star evolution. Observationally, more binary central stars of planetary nebulae have been discovered, opening new possibilities to understand the connections between binarity and morphology. So far, ≃45 binary central stars of planetary nebulae have been detected, most being close systems detected via flux variability. In order to determine the PN binary fraction, one needs a method that can detect wider binaries. We present here recent results concentrating on binary infrared excess observations aimed at detecting binaries of any separation. © 2012 International Astronomical Union.


Mian A.,University of York | Oomen R.J.F.J.,UniversiteMontpellier 2 | Isayenkov S.,University of York | Sentenac H.,UniversiteMontpellier 2 | And 2 more authors.
Plant Journal | Year: 2011

Soil salinity is an increasing menace that affects agriculture across the globe. Plant adaptation to high salt concentrations involves integrated functions, including control of Na + uptake, translocation and compartmentalization. Na + transporters belonging to the HKT family have been shown to be involved in tolerance to mild salt stress in glycophytes such as Arabidopsis, wheat and rice by contributing to Na + exclusion from aerial tissues. Here, we have analysed the role of the HKT transporter HKT2;1, which is permeable to K + and Na +, in barley, a relatively salt-tolerant crop that displays a salt-including behaviour. In Xenopus oocytes, HvHKT2;1 co-transports Na + and K + over a large range of concentrations, displaying low affinity for Na +, variable affinity for K + depending on external Na + concentration, and inhibition by K + (K i approximately 5 mM). HvHKT2;1 is predominantly expressed in the root cortex. Transcript levels are up-regulated in both roots and shoots by low K + growth conditions, and in shoots by high Na + growth conditions. Over-expression of HvHKT2;1 led to enhanced Na + uptake, higher Na + concentrations in the xylem sap, and enhanced translocation of Na + to leaves when plants were grown in the presence of 50 or 100 mM NaCl. Interestingly, these responses were correlated with increased barley salt tolerance. This suggests that one of the factors that limits barley salt tolerance is the capacity to translocate Na + to the shoot rather than accumulation or compartmentalization of this cation in leaf tissues. Thus, over-expression of HvHKT2;1 leads to increased salt tolerance by reinforcing the salt-including behaviour of barley. © 2011 Blackwell Publishing Ltd.


Blarquez O.,EPHE Paris | Blarquez O.,UniversiteMontpellier 2 | Carcaillet C.,EPHE Paris | Carcaillet C.,UniversiteMontpellier 2
PLoS ONE | Year: 2010

Background: Forecasting the effects of global changes on high altitude ecosystems requires an understanding of the longterm relationships between biota and forcing factors to identify resilience thresholds. Fire is a crucial forcing factor: both fuel build-up from land-abandonment in European mountains, and more droughts linked to global warming are likely to increase fire risks. Methods: To assess the vegetation response to fire on a millennium time-scale, we analyzed evidence of stand-to-local vegetation dynamics derived from sedimentary plant macroremains from two subalpine lakes. Paleobotanical reconstructions at high temporal resolution, together with a fire frequency reconstruction inferred from sedimentary charcoal, were analyzed by Superposed Epoch Analysis to model plant behavior before, during and after fire events. Principal Findings: We show that fuel build-up from arolla pine (Pinus cembra) always precedes fires, which is immediately followed by a rapid increase of birch (Betula sp.), then by ericaceous species after 25-75 years, and by herbs after 50-100 years. European larch (Larix decidua), which is the natural co-dominant species of subalpine forests with Pinus cembra, is not sensitive to fire, while the abundance of Pinus cembra is altered within a 150-year period after fires. A long-term trend in vegetation dynamics is apparent, wherein species that abound later in succession are the functional drivers, loading the environment with fuel for fires. This system can only be functional if fires are mainly driven by external factors (e.g. climate), with the mean interval between fires being longer than the minimum time required to reach the late successional stage, here 150 years. Conclusion: Current global warming conditions which increase drought occurrences, combined with the abandonment of land in European mountain areas, creates ideal ecological conditions for the ignition and the spread of fire. A fire return interval of less than 150 years would threaten the dominant species and might override the resilience of subalpine forests. © 2010 Blarquez, Carcaillet.


Munoz F.,UniversiteMontpellier 2 | Ramesh B.R.,French Institute of Pondicherry FIP | Couteron P.,IRD Montpellier
Ecology | Year: 2014

Understanding how local species assembly depends on the regional biogeographic and environmental context is a challenging task in community ecology. In spatially implicit neutral models, a single immigration parameter, I(k), represents the flux of immigrants from a regional pool that compete with local offspring for establishment in communities. This flux counterbalances the effect of local stochastic extinctions to maintain local species diversity. If some species within the regional pool are not adapted to the local environment (habitat filtering), the migrant flux is reduced beyond that of the neutral model, such that habitat filtering influences the value of I(k) in non-neutral situations. Here, we propose a novel model in which immigrants from the regional pool are filtered according to their habitat preferences and the local environment, while taxa potentially retain habitat preferences from their ancestors (niche conservatism). Using both analytical reasoning and simulations, we demonstrate that I(k) is expected to be constant when estimated based on the community composition at several taxonomic levels, not only under neutral assumptions, but also when habitat filtering occurs, unless there is substantial niche conservatism. In the latter case, I(k) is expected to decrease when estimated based on the composition at species to genus and family levels, thus allowing a signature of niche conservatism to be detected by simply comparing I(k) estimates across taxonomic levels. We applied this approach to three rain forest data sets from South India and Central America and found no significant signature of niche conservatism when I(k) was compared across taxonomic levels, except at the family level in South India. We further observed more limited immigration in South Indian forests, supporting the hypothesis of a greater impact of habitat filtering and heterogeneity there than in Central America. Our results highlight the relevance of studying variations of I(k) in space and across taxonomic levels to test hypotheses about the ecological and evolutionary drivers of biodiversity patterns. © 2014 by the Ecological Society of America.


Hebrard M.,French Institute of Health and Medical Research | Hebrard M.,UniversiteMontpellier 1 | Hebrard M.,UniversiteMontpellier 2 | Manes G.,French Institute of Health and Medical Research | And 16 more authors.
European Journal of Human Genetics | Year: 2011

Among inherited retinal dystrophies, autosomal recessive retinitis pigmentosa (arRP) is the most genetically heterogenous condition with 32 genes currently known that account for 60 % of patients. Molecular diagnosis thus requires the tedious systematic sequencing of 506 exons. To rapidly identify the causative mutations, we devised a strategy that combines gene mapping and phenotype assessment in small non-consanguineous families. Two unrelated sibships with arRP had whole-genome scan using SNP microchips. Chromosomal regions were selected by calculating a score based on SNP coverage and genotype identity of affected patients. Candidate genes from the regions with the highest scores were then selected based on phenotype concordance of affected patients with previously described phenotype for each candidate gene. For families RP127 and RP1459, 33 and 40 chromosomal regions showed possible linkage, respectively. By comparing the scores with the phenotypes, we ended with one best candidate gene for each family, namely tubby-like protein 1 (TULP1) and C2ORF71 for RP127 and RP1459, respectively. We found that RP127 patients were compound heterozygous for two novel TULP1 mutations, p.Arg311Gln and p.Arg342Gln, and that RP1459 patients were compound heterozygous for two novel C2ORF71 mutations, p.Leu777PhefsX34 and p.Leu777AsnfsX28. Phenotype assessment showed that TULP1 patients had severe early onset arRP and that C2ORF71 patients had a cone rod dystrophy type of arRP. Only two affected individuals in each sibship were sufficient to lead to mutation identification by screening the best candidate gene selected by a combination of gene mapping and phenotype characterization. © 2011 Macmillan Publishers Limited All rights reserved.


Malnou C.E.,French National Center for Scientific Research | Malnou C.E.,UniversiteMontpellier 2 | Malnou C.E.,UniversiteMontpellier 1 | Malnou C.E.,University Paul Sabatier | And 14 more authors.
Journal of Biological Chemistry | Year: 2010

The c-Fos proto-oncogenic transcription factor defines a multigene family controlling many processes both at the cell and the whole organism level. To bind to its target AP-1/12-O-tetradecanoylphorbol-13-acetate-responsive element or cAMP-responsive element DNA sequences in gene promoters and exert its transcriptional part, c-Fos must heterodimerize with other bZip proteins, its best studied partners being the Jun proteins (c-Jun, JunB, and JunD). c-Fos expression is regulated at many transcriptional and post-transcriptional levels, yet little is known on how its localization is dynamically regulated in the cell. Here we have investigated its intranuclear mobility using fluorescence recovery after photobleaching, genetic, and biochemical approaches. Whereas monomeric c-Fos is highly mobile and distributed evenly with nucleolar exclusion in the nucleus, heterodimerization with c-Jun entails intranuclear redistribution and dramatic reduction in mobility of c-Fos caused by predominant association with the nuclear matrix independently of any binding to AP-1/12-O-tetradecanoylphorbol-13-acetate-responsive element or cAMP-responsive element sequences. In contrast to c-Jun, dimerization with JunB does not detectably affect c-Fos mobility. However, dimerization with JunB affects intranuclear distribution with significant differences in the localization of c-Fos·c-Jun and c-Fos·JunB dimers. Moreover, c-Jun and JunB exert comparable effects on another Fos family member, Fra-1. Thus, we report a novel regulation, i.e. differentially regulated intranuclear mobility and distribution of Fos proteins by their Jun partners, and suggest the existence of intranuclear storage sites for latent c-Fos·c-Jun AP-1 complexes. This may affect the numerous physiopathological functions these transcription factors control. © 2010 by The American Society for Biochemistry and Molecular Biology, Inc.

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