Publications by authors named "Ludovic Legrand"

21 Publications

  • Page 1 of 1

Convergent Rewiring of the Virulence Regulatory Network Promotes Adaptation of Ralstonia solanacearum on Resistant Tomato.

Mol Biol Evol 2021 05;38(5):1792-1808

LIPME, Université de Toulouse, INRAE, CNRS, Castanet-Tolosan, France.

The evolutionary and adaptive potential of a pathogen is a key determinant for successful host colonization and proliferation but remains poorly known for most of the pathogens. Here, we used experimental evolution combined with phenotyping, genomics, and transcriptomics to estimate the adaptive potential of the bacterial plant pathogen Ralstonia solanacearum to overcome the quantitative resistance of the tomato cultivar Hawaii 7996. After serial passaging over 300 generations, we observed pathogen adaptation to within-plant environment of the resistant cultivar but no plant resistance breakdown. Genomic sequence analysis of the adapted clones revealed few genetic alterations, but we provide evidence that all but one were gain of function mutations. Transcriptomic analyses revealed that even if different adaptive events occurred in independently evolved clones, there is convergence toward a global rewiring of the virulence regulatory network as evidenced by largely overlapping gene expression profiles. A subset of four transcription regulators, including HrpB, the activator of the type 3 secretion system regulon and EfpR, a global regulator of virulence and metabolic functions, emerged as key nodes of this regulatory network that are frequently targeted to redirect the pathogen's physiology and improve its fitness in adverse conditions. Significant transcriptomic variations were also detected in evolved clones showing no genomic polymorphism, suggesting that epigenetic modifications regulate expression of some of the virulence network components and play a major role in adaptation as well.
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http://dx.doi.org/10.1093/molbev/msaa320DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8097285PMC
May 2021

Identification of the First Oomycete Mating-type Locus Sequence in the Grapevine Downy Mildew Pathogen, Plasmopara viticola.

Curr Biol 2020 10 13;30(20):3897-3907.e4. Epub 2020 Aug 13.

SAVE, INRAE, Bordeaux Sciences Agro, Université de Bordeaux, F-33140 Villenave d'Ornon, France. Electronic address:

Mating types are self-incompatibility systems that promote outcrossing in plants, fungi, and oomycetes. Mating-type genes have been widely studied in plants and fungi but have yet to be identified in oomycetes, eukaryotic organisms closely related to brown algae that cause many destructive animal and plant diseases. We identified the mating-type locus of Plasmopara viticola, the oomycete responsible for grapevine downy mildew, one of the most damaging grapevine diseases worldwide. Using a genome-wide association approach, we identified a 570-kb repeat-rich non-recombining region controlling mating types, with two highly divergent alleles. We showed that one mating type was homozygous, whereas the other was heterozygous at this locus. The mating-type locus encompassed 40 genes, including one encoding a putative hormone receptor. Functional studies will, however, be required to validate the function of these genes and find the actual determinants of mating type. Our findings have fundamental implications for our understanding of the evolution of mating types, as they reveal a unique determinism involving an asymmetry of heterozygosity, as in sex chromosomes and unlike other mating-type systems. This identification of the mating-type locus in such an economically important crop pathogen also has applied implications, as outcrossing facilitates rapid evolution and resistance to harsh environmental conditions.
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http://dx.doi.org/10.1016/j.cub.2020.07.057DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7116238PMC
October 2020

A secreted WY-domain-containing protein present in European isolates of the oomycete Plasmopara viticola induces cell death in grapevine and tobacco species.

PLoS One 2019 29;14(7):e0220184. Epub 2019 Jul 29.

SVQV, Université de Strasbourg, INRA, Colmar, France.

Plasmopara viticola is a biotrophic oomycete pathogen causing grapevine downy mildew. We characterized the repertoire of P. viticola effector proteins which may be translocated into plants to support the disease. We found several secreted proteins that contain canonical dEER motifs and conserved WY-domains but lack the characteristic RXLR motif reported previously from oomycete effectors. We cloned four candidates and showed that one of them, Pv33, induces plant cell death in grapevine and Nicotiana species. This activity is dependent on the nuclear localization of the protein. Sequence similar effectors were present in seven European, but in none of the tested American isolates. Together our work contributes a new type of conserved P. viticola effector candidates.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0220184PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6663016PMC
March 2020

Whole-genome sequencing reveals recent and frequent genetic recombination between clonal lineages of Cryphonectria parasitica in western Europe.

Fungal Genet Biol 2019 09 5;130:122-133. Epub 2019 Jun 5.

BIOGECO, INRA, Université de Bordeaux, 69 route d'Arcachon, Cestas F-33610, France.

Changes in the mode of reproduction are frequently observed in invasive fungal populations. The ascomycete Cryphonectria parasitica, which causes Chestnut Blight, was introduced to Europe from North America and Asia in the 20th century. Previous genotyping studies based on ten microsatellite markers have identified several clonal lineages which have spread throughout western Europe, suggesting that asexuality was the main reproductive mode of this species during colonization, although occasional sexual reproduction is not excluded. Based on the whole-genome sequences alignment of 46 C. parasitica isolates from France, North America and Asia, genealogy and population structure analyses mostly confirmed these lineages as clonal. However, one of these clonal lineages showed a signal of strong recombination, suggesting different strategies of reproduction in western Europe. Signatures of several recent recombination events within all the French clonal lineages studied here were also identified, indicating that gene flow is regular between these lineages. In addition, haplotype identification of seven French clonal lineages revealed that emergences of new clonal lineages during colonization were the result of hybridization between the main expanding clonal lineages and minor haplotypes non-sequenced in the present study. This whole-genome sequencing study underlines the importance of recombination events in the invasive success of these clonal populations, and suggests that sexual reproduction may be more frequent within and between the western European clonal lineages of C. parasitica than previously assumed using few genetic markers.
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http://dx.doi.org/10.1016/j.fgb.2019.06.002DOI Listing
September 2019

Computational analysis of the Plasmodiophora brassicae genome: mitochondrial sequence description and metabolic pathway database design.

Genomics 2019 12 15;111(6):1629-1640. Epub 2018 Nov 15.

IGEPP, INRA, AGROCAMPUS OUEST, Université Rennes, Domaine de la Motte, Le Rheu F-35653, France.

Plasmodiophora brassicae is an obligate biotrophic pathogenic protist responsible for clubroot, a root gall disease of Brassicaceae species. In addition to the reference genome of the P. brassicae European e3 isolate and the draft genomes of Canadian or Chinese isolates, we present the genome of eH, a second European isolate. Refinement of the annotation of the eH genome led to the identification of the mitochondrial genome sequence, which was found to be bigger than that of Spongospora subterranea, another plant parasitic Plasmodiophorid phylogenetically related to P. brassicae. New pathways were also predicted, such as those for the synthesis of spermidine, a polyamine up-regulated in clubbed regions of roots. A P. brassicae pathway genome database was created to facilitate the functional study of metabolic pathways in transcriptomics approaches. These available tools can help in our understanding of the regulation of P. brassicae metabolism during infection and in response to diverse constraints.
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http://dx.doi.org/10.1016/j.ygeno.2018.11.013DOI Listing
December 2019

Sunflower resistance to multiple downy mildew pathotypes revealed by recognition of conserved effectors of the oomycete Plasmopara halstedii.

Plant J 2019 02 7;97(4):730-748. Epub 2019 Jan 7.

LIPM Laboratoire des Interactions Plantes-Microorganismes, Université de Toulouse, INRA, CNRS, F-31326, Castanet-Tolosan, France.

Over the last 40 years, new sunflower downy mildew isolates (Plasmopara halstedii) have overcome major gene resistances in sunflower, requiring the identification of additional and possibly more durable broad-spectrum resistances. Here, 354 RXLR effectors defined in silico from our new genomic data were classified in a network of 40 connected components sharing conserved protein domains. Among 205 RXLR effector genes encoding conserved proteins in 17 P. halstedii pathotypes of varying virulence, we selected 30 effectors that were expressed during plant infection as potentially essential genes to target broad-spectrum resistance in sunflower. The transient expression of the 30 core effectors in sunflower and in Nicotiana benthamiana leaves revealed a wide diversity of targeted subcellular compartments, including organelles not so far shown to be targeted by oomycete effectors such as chloroplasts and processing bodies. More than half of the 30 core effectors were able to suppress pattern-triggered immunity in N. benthamiana, and five of these induced hypersensitive responses (HR) in sunflower broad-spectrum resistant lines. HR triggered by PhRXLRC01 co-segregated with Pl22 resistance in F3 populations and both traits localized in 1.7 Mb on chromosome 13 of the sunflower genome. Pl22 resistance was physically mapped on the sunflower genome recently sequenced, unlike all the other downy mildew resistances published so far. PhRXLRC01 and Pl22 are proposed as an avirulence/resistance gene couple not previously described in sunflower. Core effector recognition is a successful strategy to accelerate broad-spectrum resistance gene identification in complex crop genomes such as sunflower.
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http://dx.doi.org/10.1111/tpj.14157DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6849628PMC
February 2019

The complete methylome of an entomopathogenic bacterium reveals the existence of loci with unmethylated Adenines.

Sci Rep 2018 08 14;8(1):12091. Epub 2018 Aug 14.

DGIMI, INRA, Univ. Montpellier, Montpellier, France.

DNA methylation can serve to control diverse phenomena in eukaryotes and prokaryotes, including gene regulation leading to cell differentiation. In bacteria, DNA methylomes (i.e., methylation state of each base of the whole genome) have been described for several species, but methylome profile variation during the lifecycle has rarely been studied, and only in a few model organisms. Moreover, major phenotypic changes have been reported in several bacterial strains with a deregulated methyltransferase, but the corresponding methylome has rarely been described. Here we report the first methylome description of an entomopathogenic bacterium, Photorhabdus luminescens. Eight motifs displaying a high rate of methylation (>94%) were identified. The methylome was strikingly stable over course of growth, but also in a subpopulation responsible for a critical step in the bacterium's lifecycle: successful survival and proliferation in insects. The rare unmethylated GATC motifs were preferentially located in putative promoter regions, and most of them were methylated after Dam methyltransferase overexpression, suggesting that DNA methylation is involved in gene regulation. Our findings bring key insight into bacterial methylomes and encourage further research to decipher the role of loci protected from DNA methylation in gene regulation.
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http://dx.doi.org/10.1038/s41598-018-30620-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6092372PMC
August 2018

Comparison of GWAS models to identify non-additive genetic control of flowering time in sunflower hybrids.

Theor Appl Genet 2018 Feb 2;131(2):319-332. Epub 2017 Nov 2.

LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France.

Key Message: This study compares five models of GWAS, to show the added value of non-additive modeling of allelic effects to identify genomic regions controlling flowering time of sunflower hybrids. Genome-wide association studies are a powerful and widely used tool to decipher the genetic control of complex traits. One of the main challenges for hybrid crops, such as maize or sunflower, is to model the hybrid vigor in the linear mixed models, considering the relatedness between individuals. Here, we compared two additive and three non-additive association models for their ability to identify genomic regions associated with flowering time in sunflower hybrids. A panel of 452 sunflower hybrids, corresponding to incomplete crossing between 36 male lines and 36 female lines, was phenotyped in five environments and genotyped for 2,204,423 SNPs. Intra-locus effects were estimated in multi-locus models to detect genomic regions associated with flowering time using the different models. Thirteen quantitative trait loci were identified in total, two with both model categories and one with only non-additive models. A quantitative trait loci on LG09, detected by both the additive and non-additive models, is located near a GAI homolog and is presented in detail. Overall, this study shows the added value of non-additive modeling of allelic effects for identifying genomic regions that control traits of interest and that could participate in the heterosis observed in hybrids.
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http://dx.doi.org/10.1007/s00122-017-3003-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5787229PMC
February 2018

Genomic Prediction of Sunflower Hybrids Oil Content.

Front Plant Sci 2017 21;8:1633. Epub 2017 Sep 21.

LIPM, Université de Toulouse, INRA, Centre National de la Recherche ScientifiqueCastanet-Tolosan, France.

Prediction of hybrid performance using incomplete factorial mating designs is widely used in breeding programs including different heterotic groups. Based on the general combining ability (GCA) of the parents, predictions are accurate only if the genetic variance resulting from the specific combining ability is small and both parents have phenotyped descendants. Genomic selection (GS) can predict performance using a model trained on both phenotyped and genotyped hybrids that do not necessarily include all hybrid parents. Therefore, GS could overcome the issue of unknown parent GCA. Here, we compared the accuracy of classical GCA-based and genomic predictions for oil content of sunflower seeds using several GS models. Our study involved 452 sunflower hybrids from an incomplete factorial design of 36 female and 36 male lines. Re-sequencing of parental lines allowed to identify 468,194 non-redundant SNPs and to infer the hybrid genotypes. Oil content was observed in a multi-environment trial (MET) over 3 years, leading to nine different environments. We compared GCA-based model to different GS models including female and male genomic kinships with the addition of the female-by-male interaction genomic kinship, the use of functional knowledge as SNPs in genes of oil metabolic pathways, and with epistasis modeling. When both parents have descendants in the training set, the predictive ability was high even for GCA-based prediction, with an average MET value of 0.782. GS performed slightly better (+0.2%). Neither the inclusion of the female-by-male interaction, nor functional knowledge of oil metabolism, nor epistasis modeling improved the GS accuracy. GS greatly improved predictive ability when one or both parents were untested in the training set, increasing GCA-based predictive ability by 10.4% from 0.575 to 0.635 in the MET. In this scenario, performing GS only considering SNPs in oil metabolic pathways did not improve whole genome GS prediction but increased GCA-based prediction ability by 6.4%. Our results show that GS is a major improvement to breeding efficiency compared to the classical GCA modeling when either one or both parents are not well-characterized. This finding could therefore accelerate breeding through reducing phenotyping efforts and more effectively targeting for the most promising crosses.
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http://dx.doi.org/10.3389/fpls.2017.01633DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5613134PMC
September 2017

Alienness: Rapid Detection of Candidate Horizontal Gene Transfers across the Tree of Life.

Genes (Basel) 2017 Sep 29;8(10). Epub 2017 Sep 29.

INRA, CNRS, ISA, Université Côte d'Azur, 06903 Sophia Antipolis Cedex, France.

Horizontal gene transfer (HGT) is the transmission of genes between organisms by other means than parental to offspring inheritance. While it is prevalent in prokaryotes, HGT is less frequent in eukaryotes and particularly in Metazoa. Here, we propose Alienness, a taxonomy-aware web application available at http://alienness.sophia.inra.fr. Alienness parses BLAST results against public libraries to rapidly identify candidate HGT in any genome of interest. Alienness takes as input the result of a BLAST of a whole proteome of interest against any National Center for Biotechnology Information (NCBI) protein library. The user defines recipient (e.g., Metazoa) and donor (e.g., bacteria, fungi) branches of interest in the NCBI taxonomy. Based on the best BLAST E-values of candidate donor and recipient taxa, Alienness calculates an Alien Index (AI) for each query protein. An AI > 0 indicates a better hit to candidate donor than recipient taxa and a possible HGT. Higher AI represent higher gap of E-values between candidate donor and recipient and a more likely HGT. We confirmed the accuracy of Alienness on phylogenetically confirmed HGT of non-metazoan origin in plant-parasitic nematodes. Alienness scans whole proteomes to rapidly identify possible HGT in any species of interest and thus fosters exploration of HGT more easily and largely across the tree of life.
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http://dx.doi.org/10.3390/genes8100248DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5664098PMC
September 2017

The sunflower genome provides insights into oil metabolism, flowering and Asterid evolution.

Nature 2017 06 22;546(7656):148-152. Epub 2017 May 22.

Department of Plant Sciences, University of California, Davis, California 95616, USA.

The domesticated sunflower, Helianthus annuus L., is a global oil crop that has promise for climate change adaptation, because it can maintain stable yields across a wide variety of environmental conditions, including drought. Even greater resilience is achievable through the mining of resistance alleles from compatible wild sunflower relatives, including numerous extremophile species. Here we report a high-quality reference for the sunflower genome (3.6 gigabases), together with extensive transcriptomic data from vegetative and floral organs. The genome mostly consists of highly similar, related sequences and required single-molecule real-time sequencing technologies for successful assembly. Genome analyses enabled the reconstruction of the evolutionary history of the Asterids, further establishing the existence of a whole-genome triplication at the base of the Asterids II clade and a sunflower-specific whole-genome duplication around 29 million years ago. An integrative approach combining quantitative genetics, expression and diversity data permitted development of comprehensive gene networks for two major breeding traits, flowering time and oil metabolism, and revealed new candidate genes in these networks. We found that the genomic architecture of flowering time has been shaped by the most recent whole-genome duplication, which suggests that ancient paralogues can remain in the same regulatory networks for dozens of millions of years. This genome represents a cornerstone for future research programs aiming to exploit genetic diversity to improve biotic and abiotic stress resistance and oil production, while also considering agricultural constraints and human nutritional needs.
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http://dx.doi.org/10.1038/nature22380DOI Listing
June 2017

Comparative Analysis of Methylomes.

Front Plant Sci 2017 13;8:504. Epub 2017 Apr 13.

Center for Research in Agricultural Genomics, CSIC- IRTA- UAB -UBBarcelona, Spain.

is an important soil-borne plant pathogen with broad geographical distribution and the ability to cause wilt disease in many agriculturally important crops. Genome sequencing of multiple strains has identified both unique and shared genetic traits influencing their evolution and ability to colonize plant hosts. Previous research has shown that DNA methylation can drive speciation and modulate virulence in bacteria, but the impact of epigenetic modifications on the diversification and pathogenesis of is unknown. Sequencing of strains GMI1000 and UY031 using Single Molecule Real-Time technology allowed us to perform a comparative analysis of methylomes. Our analysis identified a novel methylation motif associated with a DNA methylase that is conserved in all complete spp. genomes and across the , as well as a methylation motif associated to a phage-borne methylase unique to UY031. Comparative analysis of the conserved methylation motif revealed that it is most prevalent in gene promoter regions, where it displays a high degree of conservation detectable through phylogenetic footprinting. Analysis of hyper- and hypo-methylated loci identified several genes involved in global and virulence regulatory functions whose expression may be modulated by DNA methylation. Analysis of genome-wide modification patterns identified a significant correlation between DNA modification and transposase genes in UY031, driven by the presence of a high copy number of ISrso3 insertion sequences in this genome and pointing to a novel mechanism for regulation of transposition. These results set a firm foundation for experimental investigations into the role of DNA methylation in evolution and its adaptation to different plants.
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http://dx.doi.org/10.3389/fpls.2017.00504DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5390034PMC
April 2017

Genetic control of plasticity of oil yield for combined abiotic stresses using a joint approach of crop modelling and genome-wide association.

Plant Cell Environ 2017 Oct 24;40(10):2276-2291. Epub 2017 Aug 24.

LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, F-31326, France.

Understanding the genetic basis of phenotypic plasticity is crucial for predicting and managing climate change effects on wild plants and crops. Here, we combined crop modelling and quantitative genetics to study the genetic control of oil yield plasticity for multiple abiotic stresses in sunflower. First, we developed stress indicators to characterize 14 environments for three abiotic stresses (cold, drought and nitrogen) using the SUNFLO crop model and phenotypic variations of three commercial varieties. The computed plant stress indicators better explain yield variation than descriptors at the climatic or crop levels. In those environments, we observed oil yield of 317 sunflower hybrids and regressed it with three selected stress indicators. The slopes of cold stress norm reaction were used as plasticity phenotypes in the following genome-wide association study. Among the 65 534 tested Single Nucleotide Polymorphisms (SNPs), we identified nine quantitative trait loci controlling oil yield plasticity to cold stress. Associated single nucleotide polymorphisms are localized in genes previously shown to be involved in cold stress responses: oligopeptide transporters, lipid transfer protein, cystatin, alternative oxidase or root development. This novel approach opens new perspectives to identify genomic regions involved in genotype-by-environment interaction of a complex traits to multiple stresses in realistic natural or agronomical conditions.
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http://dx.doi.org/10.1111/pce.12961DOI Listing
October 2017

An antimicrobial peptide-resistant minor subpopulation of Photorhabdus luminescens is responsible for virulence.

Sci Rep 2017 03 2;7:43670. Epub 2017 Mar 2.

DGIMI, INRA, Univ. Montpellier, Montpellier, France.

Some of the bacterial cells in isogenic populations behave differently from others. We describe here how a new type of phenotypic heterogeneity relating to resistance to cationic antimicrobial peptides (CAMPs) is determinant for the pathogenic infection process of the entomopathogenic bacterium Photorhabdus luminescens. We demonstrate that the resistant subpopulation, which accounts for only 0.5% of the wild-type population, causes septicemia in insects. Bacterial heterogeneity is driven by the PhoPQ two-component regulatory system and expression of pbgPE, an operon encoding proteins involved in lipopolysaccharide (LPS) modifications. We also report the characterization of a core regulon controlled by the DNA-binding PhoP protein, which governs virulence in P. luminescens. Comparative RNAseq analysis revealed an upregulation of marker genes for resistance, virulence and bacterial antagonism in the pre-existing resistant subpopulation, suggesting a greater ability to infect insect prey and to survive in cadavers. Finally, we suggest that the infection process of P. luminescens is based on a bet-hedging strategy to cope with the diverse environmental conditions experienced during the lifecycle.
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http://dx.doi.org/10.1038/srep43670DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5333078PMC
March 2017

Draft Genome Sequence of Plasmopara viticola, the Grapevine Downy Mildew Pathogen.

Genome Announc 2016 Sep 22;4(5). Epub 2016 Sep 22.

SAVE, Bordeaux Sciences Agro, INRA, Villenave d'Ornon, France.

Plasmopara viticola is a biotrophic pathogenic oomycete responsible for grapevine downy mildew. We present here the first draft of the P. viticola genome. Analysis of this sequence will help in understanding plant-pathogen interactions in oomycetes, especially pathogen host specialization and adaptation to host resistance.
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http://dx.doi.org/10.1128/genomeA.00987-16DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5034131PMC
September 2016

Design of Laccase-Metal Organic Framework-Based Bioelectrodes for Biocatalytic Oxygen Reduction Reaction.

ACS Appl Mater Interfaces 2016 Aug 29;8(31):20012-22. Epub 2016 Jul 29.

Institut Lavoisier de Versailles, UMR CNRS 8180, Université de Versailles St Quentin en Yvelines, Université Paris Saclay , 45 Avenue des Etats-Unis 78035 Versailles Cedex, France.

Laccase in combination with 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) as a mediator is a well-known bioelectrocatalyst for the 4-electron oxygen reduction reactions (ORR). The present work deals with the first exploitation of mesoporous iron(III) trimesate-based metal organic frameworks (MOF) MIL-100(Fe) (MIL stands for materials from Institut Lavoisier) as a new and efficient immobilization matrix of laccase for the building up of biocathodes for ORR. First, the immobilization of ABTS in the pores of the MOF was studied by combining micro-Raman spectroscopy, X-ray powder diffraction (XRPD), and N2 porosimetry. The ABTS-MIL-100(Fe)-based modified electrode presents excellent properties in terms of charge transfer kinetics and ionic conductivity as well as a very stable and reproducible electrochemical response, showing that MIL-100(Fe) provides a suitable and stabilizing microenvironment for electroactive ABTS molecules. In a second step, laccase was further immobilized on the MIL-100(Fe)-ABTS matrix. The Lac-ABTS-MIL-100(Fe)-CIE bioelectrode presents a high electrocatalytic current density of oxygen reduction and a reproducible electrochemical response characterized by a high stability over a long period of time (3 weeks). These results constitute a significant advance in the field of laccase-based bioelectrocatalysts for ORR. According to our work, it appears that the high catalytic efficiency of Lac-ABTS-MIL-100(Fe) for ORR may result from a synergy of chemical and catalytic properties of MIL-100(Fe) and laccase.
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http://dx.doi.org/10.1021/acsami.6b05289DOI Listing
August 2016

Design of metal organic framework-enzyme based bioelectrodes as a novel and highly sensitive biosensing platform.

J Mater Chem B 2015 Dec 22;3(46):8983-8992. Epub 2015 Oct 22.

CNRS UMR 8587 Bd François Mitterrand 91025 Evry, France.

Nanocomposites combining the mesoporous iron(iii) trimesate MIL-100(Fe) (MIL: Matériaux Institut Lavoisier) and platinum nanoparticles (Pt-NPs) have been used as immobilization matrices of glucose oxidase (GOx). Due to the physico-chemical properties of Pt-NPs (electroactivity) and MIL-100(Fe) (high specific surface area and pore volume, biocompatibility), the resulting GOx-MIL-100(Fe)-PtNP bioelectrode exhibits excellent electrocatalytic performances for glucose detection. This novel glucose biosensor presents a high sensitivity of 71 mA M cm under optimum conditions and a low limit of detection of 5 μM with low response time (<5 s). In contrast, substitution of iron by chromium or aluminum in MIL-100 leads to a much lower sensitivity and higher response time values, suggesting that the iron centres of MIL-100(Fe) may be involved in a synergistic effect which indeed enhances the catalytic oxidation of glucose and biosensor activity. Thus, this work extends the scope of MOF nanoparticles with engineered cores and surface to the field of highly sensitive, durable glucose biosensors.
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http://dx.doi.org/10.1039/c5tb01412cDOI Listing
December 2015

New one-pot synthesis of Au and Ag nanoparticles using green rust reactive particle as a micro-reactor.

Nanoscale Res Lett 2013 Feb 22;8(1):95. Epub 2013 Feb 22.

LAMBE UMR8587, CNRS-CEA-Université Evry, 1, rue du Père Jarlan, Evry Cedex 91025, France.

A new, simple, and fast one-pot synthesis of supported Au or Ag nanoparticles is implemented, for which a reactive Fe(II)-bearing green rust inorganic particle is used as an individual micro-reactor acting as both the reducing agent and support for the resulting metal nanoparticles. The mechanism involves both the solid-state oxidation of the green rust support (sulfate or carbonate) and the reduction-precipitation of soluble metal precursor. The resulting nanohybrids have a platy inorganic part supporting about one to ten nanoparticles with sizes in the 20 to 120 nm range.
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http://dx.doi.org/10.1186/1556-276X-8-95DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3599552PMC
February 2013

BioMAJ: a flexible framework for databanks synchronization and processing.

Bioinformatics 2008 Aug 30;24(16):1823-5. Epub 2008 Jun 30.

IRISA/INRIA, Symbiose Project, Unité de Biométrie et Intelligence Artificielle, UR875, INRA, F-31320 Castanet-Tolosan, France.

Unlabelled: Large- and medium-scale computational molecular biology projects require accurate bioinformatics software and numerous heterogeneous biological databanks, which are distributed around the world. BioMAJ provides a flexible, robust, fully automated environment for managing such massive amounts of data. The JAVA application enables automation of the data update cycle process and supervision of the locally mirrored data repository. We have developed workflows that handle some of the most commonly used bioinformatics databases. A set of scripts is also available for post-synchronization data treatment consisting of indexation or format conversion (for NCBI blast, SRS, EMBOSS, GCG, etc.). BioMAJ can be easily extended by personal homemade processing scripts. Source history can be kept via html reports containing statements of locally managed databanks.

Availability: http://biomaj.genouest.org. BioMAJ is free open software. It is freely available under the CECILL version 2 license.
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http://dx.doi.org/10.1093/bioinformatics/btn325DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3293366PMC
August 2008

Working memory after severe traumatic brain injury.

J Int Neuropsychol Soc 2007 Sep;13(5):770-80

Antenne UEROS-UGECAM Hôpital Raymond Poincaré, Garches, INSERM U 731, and Université Paris 6, Faculté de Médecine, Laboratoire de Physiologie et Physiopathologie de la Motricité, Paris, France.

The aim of the present study was to assess the functioning of the different subsystems of working memory after severe traumatic brain injury (TBI). A total of 30 patients with severe chronic TBI and 28 controls received a comprehensive assessment of working memory addressing the phonological loop (forward and backward digit span; word length and phonological similarity effects), the visuospatial sketchpad (forward and backward visual spans), and the central executive (tasks requiring simultaneous storage and processing of information, dual-task processing, working memory updating). Results showed that there were only marginal group differences regarding the functioning of the two slave systems, whereas patients with severe TBI performed significantly poorer than controls on most central executive tasks, particularly on those requiring a high level of controlled processing. These results suggest that severe TBI is associated with an impairment of executive aspects of working memory. The anatomic substrate of this impairment remains to be elucidated. It might be related to a defective activation of a distributed network, including the dorsolateral prefrontal cortex.
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http://dx.doi.org/10.1017/S1355617707070993DOI Listing
September 2007

Reduction of aqueous chromate by Fe(II)/Fe(III) carbonate green rust: kinetic and mechanistic studies.

Environ Sci Technol 2004 Sep;38(17):4587-95

Laboratoire Analyse et Environnement, UMR 8587 CNRS-Université d'Evry Val d'Essonne-CEA, Bâtiment des Sciences, 1 Rue du Père Jarland, 91025 Evry Cedex, France.

This work describes the heterogeneous reaction between FeII in carbonate green rust and aqueous chromate, in NaHCO3 solutions at 25 degrees C, and at pH values of 9.3-9.6. Evidence for reduction of CrVI to CrIII and concomitant solid-state oxidation of lattice FeII to FeIII was found from FeII titration and from structural analysis of the solids using FTIR, XRD, SEM, and XPS methods. Results indicate the formation of ferric oxyhydroxycarbonate and the concomitant precipitation of CrIII monolayers at the surface of the iron compound that induce passivation effects and progressive rate limitations. The number of CrIII monolayers formed at the completion of the reaction depends on [FeII]t=0, the molar concentration of FeII(solid) at t=0; on [n(o)]t=0, the molar concentration of reaction sites present at the surface of the solid phase at t=0; and on [CrVI]t=0, the molar concentration of CrVI at t=0. Kinetic data were modeled using a model based on the formation of successive CrIII monolayers, -(d[CrVI]/dt) = sigma(1)j k(i)[S] [CrVI]([n(i - 1)] - [n(i)]) with k(i)[S] (in s(-1) L mol(-1)), the rate coefficient of formation of CrIII monolayer i, and [n(i)] and [n(i - 1)], the molar concentration of CrIII precipitated in monolayer i and monolayer i - 1, respectively. Good matching curves were obtained with kinetic coefficients: k(1)[S] = 5-8 x 10(-4), k(2)[S] = 0.5-3 x 10(-5), and k(3)[S] about 1.7 x 10(-6) s(-1) m(-2) L. The CrVI removal efficiency progressively decreases along with the accumulation of CrIII monolayers at the surface of carbonate green rust particles. In the case of thick green rust particles resulting from the corrosion of iron in permeable reactive barriers, the quantity of FeII readily accessible for efficient CrVI removal should be rather low.
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http://dx.doi.org/10.1021/es035447xDOI Listing
September 2004