Publications by authors named "Denis Baurain"

41 Publications

Exploring syntenic conservation across genomes for phylogenetic studies of organisms subjected to horizontal gene transfers: a case study with Cyanobacteria and cyanolichens.

Mol Phylogenet Evol 2021 Feb 13:107100. Epub 2021 Feb 13.

Department of Biology, Duke University, Durham, NC, USA.

Understanding the evolutionary history of symbiotic Cyanobacteria at a fine scale is essential to unveil patterns of associations with their hosts and factors driving their spatiotemporal interactions. As for bacteria in general, Horizontal Gene Transfers (HGT) are expected to be rampant throughout their evolution, which justified the use of single-locus phylogenies in macroevolutionary studies of these photoautotrophic bacteria. Genomic approaches have greatly increased the amount of molecular data available, but the selection of orthologous, congruent genes that are more likely to reflect bacterial macroevolutionary histories remains problematic. In this study, we developed a synteny-based approach and searched for Collinear Orthologous Regions (COR), under the assumption that genes that are present in the same order and orientation across a wide monophyletic clade are less likely to have undergone HGT. We searched sixteen reference Nostocales genomes and identified 99 genes, part of 28 COR comprising three to eight genes each. We then developed a bioinformatic pipeline, designed to minimize inter-genome contamination and processed twelve Nostoc-associated lichen metagenomes. This reduced our original dataset to 90 genes representing 25 COR, which were used to infer phylogenetic relationships within Nostocales and among lichenized Cyanobacteria. This dataset was narrowed down further to 71 genes representing 22 COR by selecting only genes part of one (largest) operon per COR. We found a relatively high level of congruence among trees derived from the 90-gene dataset, but congruence was only slightly higher among genes within a COR compared to genes across COR. However, topological congruence was significantly higher among the 71 genes part of one operon per COR. Nostocales phylogenies resulting from concatenation and species tree approaches based on the 90- and 71-gene datasets were highly congruent, but the most highly supported result was obtained when using synteny, collinearity, and operon information (i.e., 71-gene dataset) as gene selection criteria, which outperformed larger datasets with more genes.
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http://dx.doi.org/10.1016/j.ympev.2021.107100DOI Listing
February 2021

Palantir: a springboard for the analysis of secondary metabolite gene clusters in large-scale genome mining projects.

Bioinformatics 2020 08;36(15):4345-4347

InBioS-PhytoSYSTEMS, Eukaryotic Phylogenomics, University of Liège, B-4000 Liège, Belgium.

Summary: To support small and large-scale genome mining projects, we present Post-processing Analysis tooLbox for ANTIsmash Reports (Palantir), a dedicated software suite for handling and refining secondary metabolite biosynthetic gene cluster (BGC) data annotated with the popular antiSMASH pipeline. Palantir provides new functionalities building on NRPS/PKS predictions from antiSMASH, such as improved BGC annotation, module delineation and easy access to sub-sequences at different levels (cluster, gene, module and domain). Moreover, it can parse user-provided antiSMASH reports and reformat them for direct use or storage in a relational database.

Availability And Implementation: Palantir is released both as a Perl API available on CPAN (https://metacpan.org/release/Bio-Palantir) and as a web application (http://palantir.uliege.be). As a practical use case, the web interface also features a database built from the mining of 1616 cyanobacterial genomes, of which 1488 were predicted to encode at least one BGC.

Supplementary Information: Supplementary data are available at Bioinformatics online.
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http://dx.doi.org/10.1093/bioinformatics/btaa517DOI Listing
August 2020

Nonribosomal peptides in fungal cell factories: from genome mining to optimized heterologous production.

Biotechnol Adv 2019 12 10;37(8):107449. Epub 2019 Sep 10.

Univ. Lille, INRA, ISA, Univ. Artois, Univ. Littoral Côte d'Opale, EA 7394-ICV-Institut Charles Viollette, F-59000 Lille, France. Electronic address:

Fungi are notoriously prolific producers of secondary metabolites including nonribosomal peptides (NRPs). The structural complexity of NRPs grants them interesting activities such as antibiotic, anti-cancer, and anti-inflammatory properties. The discovery of these compounds with attractive activities can be achieved by using two approaches: either by screening samples originating from various environments for their biological activities, or by identifying the related clusters in genomic sequences thanks to bioinformatics tools. This genome mining approach has grown tremendously due to recent advances in genome sequencing, which have provided an incredible amount of genomic data from hundreds of microbial species. Regarding fungal organisms, the genomic data have revealed the presence of an unexpected number of putative NRP-related gene clusters. This highlights fungi as a goldmine for the discovery of putative novel bioactive compounds. Recent development of NRP dedicated bioinformatics tools have increased the capacity to identify these gene clusters and to deduce NRPs structures, speeding-up the screening process for novel metabolites discovery. Unfortunately, the newly identified compound is frequently not or poorly produced by native producers due to a lack of expression of the related genes cluster. A frequently employed strategy to increase production rates consists in transferring the related biosynthetic pathway in heterologous hosts. This review aims to provide a comprehensive overview about the topic of NRPs discovery, from gene cluster identification by genome mining to the heterologous production in fungal hosts. The main computational tools and methods for genome mining are herein presented with an emphasis on the particularities of the fungal systems. The different steps of the reconstitution of NRP biosynthetic pathway in heterologous fungal cell factories will be discussed, as well as the key factors to consider for maximizing productivity. Several examples will be developed to illustrate the potential of heterologous production to both discover uncharacterized novel compounds predicted in silico by genome mining, and to enhance the productivity of interesting bio-active natural products.
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http://dx.doi.org/10.1016/j.biotechadv.2019.107449DOI Listing
December 2019

Cyanobacteria evolution: Insight from the fossil record.

Free Radic Biol Med 2019 08 9;140:206-223. Epub 2019 May 9.

Early Life Traces & Evolution - Astrobiology, UR ASTROBIOLOGY, Geology Department, University of Liège, Liège, Belgium.

Cyanobacteria played an important role in the evolution of Early Earth and the biosphere. They are responsible for the oxygenation of the atmosphere and oceans since the Great Oxidation Event around 2.4 Ga, debatably earlier. They are also major primary producers in past and present oceans, and the ancestors of the chloroplast. Nevertheless, the identification of cyanobacteria in the early fossil record remains ambiguous because the morphological criteria commonly used are not always reliable for microfossil interpretation. Recently, new biosignatures specific to cyanobacteria were proposed. Here, we review the classic and new cyanobacterial biosignatures. We also assess the reliability of the previously described cyanobacteria fossil record and the challenges of molecular approaches on modern cyanobacteria. Finally, we suggest possible new calibration points for molecular clocks, and strategies to improve our understanding of the timing and pattern of the evolution of cyanobacteria and oxygenic photosynthesis.
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http://dx.doi.org/10.1016/j.freeradbiomed.2019.05.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6880289PMC
August 2019

Evaluating the usefulness of alignment filtering methods to reduce the impact of errors on evolutionary inferences.

BMC Evol Biol 2019 01 11;19(1):21. Epub 2019 Jan 11.

Station d'Ecologie Théorique et Expérimentale de Moulis, CNRS, Moulis, France.

Background: Multiple Sequence Alignments (MSAs) are the starting point of molecular evolutionary analyses. Errors in MSAs generate a non-historical signal that can lead to incorrect inferences. Therefore, numerous efforts have been made to reduce the impact of alignment errors, by improving alignment algorithms and by developing methods to filter out poorly aligned regions. However, MSAs do not only contain alignment errors, but also primary sequence errors. Such errors may originate from sequencing errors, from assembly errors, or from erroneous structural annotations (such as incorrect intron/exon boundaries). Even though their existence is acknowledged, the impact of primary sequence errors on evolutionary inference is poorly characterized.

Results: In a first step to fill this gap, we have developed a program called HmmCleaner, which detects and eliminates these errors from MSAs. It uses profile hidden Markov models (pHMM) to identify sequence segments that poorly fit their MSA and selectively removes them. We assessed its performances using > 700 amino-acid MSAs from prokaryotes and eukaryotes, in which we introduced several types of simulated primary sequence errors. The sensitivity of HmmCleaner towards simulated primary sequence errors was > 95%. In a second step, we compared the impact of segment filtering software (HmmCleaner and PREQUAL) relative to commonly used block-filtering software (BMGE and TrimAI) on evolutionary analyses. Using real data from vertebrates, we observed that segment-filtering methods improve the quality of evolutionary inference more than the currently used block-filtering methods. The formers were especially effective at improving branch length inferences, and at reducing false positive rate during detection of positive selection.

Conclusions: Segment filtering methods such as HmmCleaner accurately detect simulated primary sequence errors. Our results suggest that these errors are more detrimental than alignment errors. However, they also show that stochastic (sampling) error is predominant in single-gene evolutionary inferences. Therefore, we argue that MSA filtering should focus on segment instead of block removal and that more studies are required to find the optimal balance between accuracy improvement and stochastic error increase brought by data removal.
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http://dx.doi.org/10.1186/s12862-019-1350-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6330419PMC
January 2019

Metagenomic assembly of new (sub)polar Cyanobacteria and their associated microbiome from non-axenic cultures.

Microb Genom 2018 09 23;4(9). Epub 2018 Aug 23.

1​InBioS - PhytoSYSTEMS, Eukaryotic Phylogenomics, University of Liège, Liège, Belgium.

Cyanobacteria form one of the most diversified phyla of Bacteria. They are important ecologically as primary producers, for Earth evolution and biotechnological applications. Yet, Cyanobacteria are notably difficult to purify and grow axenically, and most strains in culture collections contain heterotrophic bacteria that were probably associated with Cyanobacteria in the environment. Obtaining cyanobacterial DNA without contaminant sequences is thus a challenging and time-consuming task. Here, we describe a metagenomic pipeline that enables the easy recovery of genomes from non-axenic cultures. We tested this pipeline on 17 cyanobacterial cultures from the BCCM/ULC public collection and generated novel genome sequences for 12 polar or subpolar strains and three temperate ones, including three early-branching organisms that will be useful for phylogenomics. In parallel, we assembled 31 co-cultivated bacteria (12 nearly complete) from the same cultures and showed that they mostly belong to Bacteroidetes and Proteobacteria, some of them being very closely related in spite of geographically distant sampling sites.
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http://dx.doi.org/10.1099/mgen.0.000212DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6202449PMC
September 2018

Consensus assessment of the contamination level of publicly available cyanobacterial genomes.

PLoS One 2018 25;13(7):e0200323. Epub 2018 Jul 25.

InBioS-PhytoSYSTEMS, Eukaryotic Phylogenomics, University of Liège, Liège, Belgium.

Publicly available genomes are crucial for phylogenetic and metagenomic studies, in which contaminating sequences can be the cause of major problems. This issue is expected to be especially important for Cyanobacteria because axenic strains are notoriously difficult to obtain and keep in culture. Yet, despite their great scientific interest, no data are currently available concerning the quality of publicly available cyanobacterial genomes. As reliably detecting contaminants is a complex task, we designed a pipeline combining six methods in a consensus strategy to assess the contamination level of 440 genome assemblies of Cyanobacteria. Two methods are based on published reference databases of ribosomal genes (SSU rRNA 16S and ribosomal proteins), one is indirectly based on a reference database of marker genes (CheckM), and three are based on complete genome analysis. Among those genome-wide methods, Kraken and DIAMOND blastx share the same reference database that we derived from Ensembl Bacteria, whereas CONCOCT does not require any reference database, instead relying on differences in DNA tetramer frequencies. Given that all the six methods appear to have their own strengths and limitations, we used the consensus of their rankings to infer that >5% of cyanobacterial genome assemblies are highly contaminated by foreign DNA (i.e., contaminants were detected by 5 or 6 methods). Our results will help researchers to check the quality of publicly available genomic data before use in their own analyses. Moreover, we argue that journals should make mandatory the submission of raw read data along with genome assemblies in order to facilitate the detection of contaminants in sequence databases.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0200323PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6059444PMC
January 2019

A constrained SSU-rRNA phylogeny reveals the unsequenced diversity of photosynthetic Cyanobacteria (Oxyphotobacteria).

BMC Res Notes 2018 Jul 3;11(1):435. Epub 2018 Jul 3.

InBioS-PhytoSYSTEMS, Eukaryotic Phylogenomics, University of Liège, 4000, Liège, Belgium.

Objective: Cyanobacteria are an ancient phylum of prokaryotes that contain the class Oxyphotobacteria. This group has been extensively studied by phylogenomics notably because it is widely accepted that Cyanobacteria were responsible for the spread of photosynthesis to the eukaryotic domain. The aim of this study was to evaluate the fraction of the oxyphotobacterial diversity for which sequenced genomes are available for genomic studies. For this, we built a phylogenomic-constrained SSU rRNA (16S) tree to pinpoint unexploited clusters of Oxyphotobacteria that should be targeted for future genome sequencing, so as to improve our understanding of Oxyphotobacteria evolution.

Results: We show that only a little fraction of the oxyphotobacterial diversity has been sequenced so far. Indeed 31 rRNA clusters of the 60 composing the photosynthetic Cyanobacteria have a fraction of sequenced genomes < 1%. This fraction remains low (min = 1%, median = 11.1%, IQR = 7.3%) within the remaining "sequenced" clusters that already contain some representative genomes. The "unsequenced" clusters are scattered across the whole Oxyphotobacteria tree, at the exception of very basal clades. Yet, these clades still feature some (sub)clusters without any representative genome. This last result is especially important, as these basal clades are prime candidate for plastid emergence.
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http://dx.doi.org/10.1186/s13104-018-3543-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6029276PMC
July 2018

Complete Genome Sequence of Streptomyces lunaelactis MM109, Isolated from Cave Moonmilk Deposits.

Genome Announc 2018 May 24;6(21). Epub 2018 May 24.

InBioS-Centre for Protein Engineering, Institut de Chimie, University of Liège, Liège, Belgium

MM109 is a ferroverdin A (anticholesterol) producer isolated from cave moonmilk deposits. The complete genome sequence of MM109 was obtained by combining Oxford Nanopore MinION and Illumina HiSeq and MiSeq technologies, revealing an 8.4-Mb linear chromosome and two plasmids, pSLUN1 (127,264 bp, linear) and pSLUN2 (46,827 bp, circular).
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http://dx.doi.org/10.1128/genomeA.00435-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968722PMC
May 2018

Isolation, Characterization, and Antibacterial Activity of Hard-to-Culture Actinobacteria from Cave Moonmilk Deposits.

Antibiotics (Basel) 2018 Mar 22;7(2). Epub 2018 Mar 22.

Integrative Biological Sciences (InBioS), Center for Protein Engineering, Liège University, B-4000 Liège, Belgium.

Cave moonmilk deposits host an abundant and diverse actinobacterial population that has a great potential for producing novel natural bioactive compounds. In our previous attempt to isolate culturable moonmilk-dwelling Actinobacteria, only species were recovered, whereas a metagenetic study of the same deposits revealed a complex actinobacterial community including 46 actinobacterial genera in addition to streptomycetes. In this work, we applied the rehydration-centrifugation method to lessen the occurrence of filamentous species and tested a series of strategies to achieve the isolation of hard-to-culture and rare Actinobacteria from the moonmilk deposits of the cave "Grotte des Collemboles". From the "tips and tricks" that were tested, separate autoclaving of the components of the International Streptomyces Project (ISP) medium number 5 (ISP5) medium, prolonged incubation time, and dilution of the moonmilk suspension were found to most effectively improve colony forming units. Taxonomic analyses of the 40 isolates revealed new representatives of the , , , , , , and species, as well as additional new streptomycetes. The applied methodologies allowed the isolation of strains associated with both the least and most abundant moonmilk-dwelling actinobacterial operational taxonomic units. Finally, bioactivity screenings revealed that some isolates displayed high antibacterial activities, and genome mining uncovered a strong potential for the production of natural compounds.
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http://dx.doi.org/10.3390/antibiotics7020028DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6023089PMC
March 2018

High-Throughput Sequencing Analysis of the Actinobacterial Spatial Diversity in Moonmilk Deposits.

Antibiotics (Basel) 2018 Mar 21;7(2). Epub 2018 Mar 21.

InBioS-Centre for Protein Engineering, Institut de Chimie B6a, University of Liège, B-4000 Liège, Belgium.

Moonmilk are cave carbonate deposits that host a rich microbiome, including antibiotic-producing Actinobacteria, making these speleothems appealing for bioprospecting. Here, we investigated the taxonomic profile of the actinobacterial community of three moonmilk deposits of the cave "Grotte des Collemboles" via high-throughput sequencing of 16S rRNA amplicons. Actinobacteria was the most common phylum after Proteobacteria, ranging from 9% to 23% of the total bacterial population. Next to actinobacterial operational taxonomic units (OTUs) attributed to uncultured organisms at the genus level (~44%), we identified 47 actinobacterial genera with (4 OTUs, 17%) and (9 OTUs, ~16%) as the most abundant in terms of the absolute number of sequences. Streptomycetes presented the highest diversity (19 OTUs, 3%), with most of the OTUs unlinked to the culturable strains that were previously isolated from the same deposits. Furthermore, 43% of the OTUs were shared between the three studied collection points, while 34% were exclusive to one deposit, indicating that distinct speleothems host their own population, despite their nearby localization. This important spatial diversity suggests that prospecting within different moonmilk deposits should result in the isolation of unique and novel Actinobacteria. These speleothems also host a wide range of non-streptomycetes antibiotic-producing genera, and should therefore be subjected to methodologies for isolating rare Actinobacteria.
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http://dx.doi.org/10.3390/antibiotics7020027DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6023079PMC
March 2018

Number of inadvertent RNA targets for morpholino knockdown in Danio rerio is largely underestimated: evidence from the study of Ser/Arg-rich splicing factors.

Nucleic Acids Res 2017 Sep;45(16):9547-9557

Laboratory of Functional Genomics and Plant Molecular Imaging, InBioS, PhytoSystems and Centre for Assistance in Technology of Microscopy (CAREm), University of Liège, 4000 Liège, Belgium.

Although the involvement of Ser/Arg-rich (SR) proteins in RNA metabolism is well documented, their role in vertebrate development remains elusive. We, therefore, elected to take advantage of the zebrafish model organism to study the SR genes' functions using the splicing morpholino (sMO) microinjection and the programmable site-specific nucleases. Consistent with previous research, we revealed discrepancies between the mutant and morphant phenotypes and we show that these inconsistencies may result from a large number of unsuspected inadvertent morpholino RNA targets. While microinjection of MOs directed against srsf5a (sMOsrsf5a) led to developmental defects, the corresponding homozygous mutants did not display any phenotypic traits. Furthermore, microinjection of sMOsrsf5a into srsf5a-/- led to the previously observed morphant phenotype. Similar findings were observed for other SR genes. sMOsrsf5a alternative target genes were identified using deep mRNA sequencing. We uncovered that only 11 consecutive bases complementary to sMOsrsf5a are sufficient for binding and subsequent blocking of splice sites. In addition, we observed that sMOsrsf5a secondary targets can be reduced by increasing embryos growth temperature after microinjection. Our data contribute to the debate about MO specificity, efficacy and the number of unknown targeted sequences.
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http://dx.doi.org/10.1093/nar/gkx638DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5766196PMC
September 2017

Phylotranscriptomic consolidation of the jawed vertebrate timetree.

Nat Ecol Evol 2017 Sep 24;1(9):1370-1378. Epub 2017 Jul 24.

Centre for Biodiversity Theory and Modelling, UMR CNRS 5321, Station of Theoretical and Experimental Ecology, Moulis, 09200, France.

Phylogenomics is extremely powerful but introduces new challenges as no agreement exists on "standards" for data selection, curation and tree inference. We use jawed vertebrates (Gnathostomata) as model to address these issues. Despite considerable efforts in resolving their evolutionary history and macroevolution, few studies have included a full phylogenetic diversity of gnathostomes and some relationships remain controversial. We tested a novel bioinformatic pipeline to assemble large and accurate phylogenomic datasets from RNA sequencing and find this phylotranscriptomic approach successful and highly cost-effective. Increased sequencing effort up to ca. 10Gbp allows recovering more genes, but shallower sequencing (1.5Gbp) is sufficient to obtain thousands of full-length orthologous transcripts. We reconstruct a robust and strongly supported timetree of jawed vertebrates using 7,189 nuclear genes from 100 taxa, including 23 new transcriptomes from previously unsampled key species. Gene jackknifing of genomic data corroborates the robustness of our tree and allows calculating genome-wide divergence times by overcoming gene sampling bias. Mitochondrial genomes prove insufficient to resolve the deepest relationships because of limited signal and among-lineage rate heterogeneity. Our analyses emphasize the importance of large curated nuclear datasets to increase the accuracy of phylogenomics and provide a reference framework for the evolutionary history of jawed vertebrates.
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http://dx.doi.org/10.1038/s41559-017-0240-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5584656PMC
September 2017

Inferring the shallow phylogeny of true salamanders (Salamandra) by multiple phylogenomic approaches.

Mol Phylogenet Evol 2017 10 14;115:16-26. Epub 2017 Jul 14.

Zoological Institute, Braunschweig University of Technology, Mendelssohnstr. 4, 38106 Braunschweig, Germany. Electronic address:

The rise of high-throughput sequencing techniques provides the unprecedented opportunity to analyse controversial phylogenetic relationships in great depth, but also introduces a risk of being misinterpreted by high node support values influenced by unevenly distributed missing data or unrealistic model assumptions. Here, we use three largely independent phylogenomic data sets to reconstruct the controversial phylogeny of true salamanders of the genus Salamandra, a group of amphibians providing an intriguing model to study the evolution of aposematism and viviparity. For all six species of the genus Salamandra, and two outgroup species from its sister genus Lyciasalamandra, we used RNA sequencing (RNAseq) and restriction site associated DNA sequencing (RADseq) to obtain data for: (1) 3070 nuclear protein-coding genes from RNAseq; (2) 7440 loci obtained by RADseq; and (3) full mitochondrial genomes. The RNAseq and RADseq data sets retrieved fully congruent topologies when each of them was analyzed in a concatenation approach, with high support for: (1) S. infraimmaculata being sister group to all other Salamandra species; (2) S. algira being sister to S. salamandra; (3) these two species being the sister group to a clade containing S. atra, S. corsica and S. lanzai; and (4) the alpine species S. atra and S. lanzai being sister taxa. The phylogeny inferred from the mitochondrial genome sequences differed from these results, most notably by strongly supporting a clade containing S. atra and S. corsica as sister taxa. A different placement of S. corsica was also retrieved when analysing the RNAseq and RADseq data under species tree approaches. Closer examination of gene trees derived from RNAseq revealed that only a low number of them supported each of the alternative placements of S. atra. Furthermore, gene jackknife support for the S. atra - S. lanzai node stabilized only with very large concatenated data sets. The phylogeny of true salamanders thus provides a compelling example of how classical node support metrics such as bootstrap and Bayesian posterior probability can provide high confidence values in a phylogenomic topology even if the phylogenetic signal for some nodes is spurious, highlighting the importance of complementary approaches such as gene jackknifing. Yet, the general congruence among the topologies recovered from the RNAseq and RADseq data sets increases our confidence in the results, and validates the use of phylotranscriptomic approaches for reconstructing shallow relationships among closely related taxa. We hypothesize that the evolution of Salamandra has been characterized by episodes of introgressive hybridization, which would explain the difficulties of fully reconstructing their evolutionary relationships.
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http://dx.doi.org/10.1016/j.ympev.2017.07.009DOI Listing
October 2017

Assessment of the Potential Role of in Cave Moonmilk Formation.

Front Microbiol 2017 29;8:1181. Epub 2017 Jun 29.

InBioS-Centre for Protein Engineering, Institut de Chimie B6a, University of LiègeLiège, Belgium.

Moonmilk is a karstic speleothem mainly composed of fine calcium carbonate crystals (CaCO) with different textures ranging from pasty to hard, in which the contribution of biotic rock-building processes is presumed to involve indigenous microorganisms. The real microbial input in the genesis of moonmilk is difficult to assess leading to controversial hypotheses explaining the origins and the mechanisms (biotic vs. abiotic) involved. In this work, we undertook a comprehensive approach in order to assess the potential role of filamentous bacteria, particularly a collection of moonmilk-originating , in the genesis of this speleothem. Scanning electron microscopy (SEM) confirmed that indigenous filamentous bacteria could indeed participate in moonmilk development by serving as nucleation sites for CaCO deposition. The metabolic activities involved in CaCO transformation were furthermore assessed among the collection of moonmilk , which revealed that peptides/amino acids ammonification, and to a lesser extend ureolysis, could be privileged metabolic pathways participating in carbonate precipitation by increasing the pH of the bacterial environment. Additionally, search for the genes involved in biomineralization processes including ureolysis, dissimilatory nitrate reduction to ammonia, active calcium ion transport, and reversible hydration of CO allowed to identify genetic predispositions for carbonate precipitation in . Finally, their biomineralization abilities were confirmed by environmental SEM, which allowed to visualize the formation of abundant mineral deposits under laboratory conditions. Overall, our study provides novel evidences that filamentous Actinobacteria could be key protagonists in the genesis of moonmilk through a wide spectrum of biomineralization processes.
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http://dx.doi.org/10.3389/fmicb.2017.01181DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5489568PMC
June 2017

Human Chitotriosidase: Catalytic Domain or Carbohydrate Binding Module, Who's Leading HCHT's Biological Function.

Sci Rep 2017 06 5;7(1):2768. Epub 2017 Jun 5.

InBioS - Center for Protein Engineering, Department of Life Sciences, Université de Liège, Sart-Tilman, B4000, Liège, Belgium.

Chitin is an important structural component of numerous fungal pathogens and parasitic nematodes. The human macrophage chitotriosidase (HCHT) is a chitinase that hydrolyses glycosidic bonds between the N-acetyl-D-glucosamine units of this biopolymer. HCHT belongs to the Glycoside Hydrolase (GH) superfamily and contains a well-characterized catalytic domain appended to a chitin-binding domain (ChBD). Although its precise biological function remains unclear, HCHT has been described to be involved in innate immunity. In this study, the molecular basis for interaction with insoluble chitin as well as with soluble chito-oligosaccharides has been determined. The results suggest a new mechanism as a common binding mode for many Carbohydrate Binding Modules (CBMs). Furthermore, using a phylogenetic approach, we have analysed the modularity of HCHT and investigated the evolutionary paths of its catalytic and chitin binding domains. The phylogenetic analyses indicate that the ChBD domain dictates the biological function of HCHT and not its appended catalytic domain. This observation may also be a general feature of GHs. Altogether, our data have led us to postulate and discuss that HCHT acts as an immune catalyser.
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http://dx.doi.org/10.1038/s41598-017-02382-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5459812PMC
June 2017

A Large and Consistent Phylogenomic Dataset Supports Sponges as the Sister Group to All Other Animals.

Curr Biol 2017 Apr 16;27(7):958-967. Epub 2017 Mar 16.

Sorbonne Universités, UPMC Univ Paris 06, CNRS, Evolution Paris-Seine UMR7138, Institut de Biologie Paris-Seine, Case 05, 7 quai St Bernard, 75005 Paris, France. Electronic address:

Resolving the early diversification of animal lineages has proven difficult, even using genome-scale datasets. Several phylogenomic studies have supported the classical scenario in which sponges (Porifera) are the sister group to all other animals ("Porifera-sister" hypothesis), consistent with a single origin of the gut, nerve cells, and muscle cells in the stem lineage of eumetazoans (bilaterians + ctenophores + cnidarians). In contrast, several other studies have recovered an alternative topology in which ctenophores are the sister group to all other animals (including sponges). The "Ctenophora-sister" hypothesis implies that eumetazoan-specific traits, such as neurons and muscle cells, either evolved once along the metazoan stem lineage and were then lost in sponges and placozoans or evolved at least twice independently in Ctenophora and in Cnidaria + Bilateria. Here, we report on our reconstruction of deep metazoan relationships using a 1,719-gene dataset with dense taxonomic sampling of non-bilaterian animals that was assembled using a semi-automated procedure, designed to reduce known error sources. Our dataset outperforms previous metazoan gene superalignments in terms of data quality and quantity. Analyses with a best-fitting site-heterogeneous evolutionary model provide strong statistical support for placing sponges as the sister-group to all other metazoans, with ctenophores emerging as the second-earliest branching animal lineage. Only those methodological settings that exacerbated long-branch attraction artifacts yielded Ctenophora-sister. These results show that methodological issues must be carefully addressed to tackle difficult phylogenetic questions and pave the road to a better understanding of how fundamental features of animal body plans have emerged.
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http://dx.doi.org/10.1016/j.cub.2017.02.031DOI Listing
April 2017

Draft Genome Sequence of the Axenic Strain ULC007, a Cyanobacterium Isolated from Lake Bruehwiler (Larsemann Hills, Antarctica).

Genome Announc 2017 Feb 16;5(7). Epub 2017 Feb 16.

InBioS-Centre for Protein Engineering, University of Liège, Liège, Belgium

ULC007 is an Antarctic freshwater cyanobacterium. Its draft genome is 5,684,389 bp long. It contains a total of 5,604 protein-encoding genes, of which 22.2% have no clear homologues in known genomes. To date, this draft genome is the first one ever determined for an axenic cyanobacterium from Antarctica.
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http://dx.doi.org/10.1128/genomeA.01546-16DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5313606PMC
February 2017

High-throughput sequencing analysis reveals the genetic diversity of different regions of the murine norovirus genome during in vitro replication.

Arch Virol 2017 Apr 9;162(4):1019-1023. Epub 2016 Dec 9.

Veterinary Virology and Animal Viral Diseases, Fundamental and Applied Research for Animal & Health Centre, Faculty of Veterinary Medicine, University of Liège, Liège, Belgium.

In this study, we report the genetic diversity and nucleotide mutation rates of five representative regions of the murine norovirus genome during in vitro passages. The mutation rates were similar in genomic regions encompassing partial coding sequences for non-structural (NS) 1-2, NS5, NS6, NS7 proteins within open reading frame (ORF) 1. In a region encoding a portion of the major capsid protein (VP1) within ORF2 (also including the ORF4 region) and a portion of the minor structural protein (VP2), the mutation rates were estimated to be at least one order of magnitude higher. The VP2 coding region was found to have the highest mutation rate.
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http://dx.doi.org/10.1007/s00705-016-3179-yDOI Listing
April 2017

A Phenotypic and Genotypic Analysis of the Antimicrobial Potential of Cultivable Isolated from Cave Moonmilk Deposits.

Front Microbiol 2016 21;7:1455. Epub 2016 Sep 21.

InBioS - Centre for Protein Engineering, Institut de Chimie B6a, University of Liège Liège, Belgium.

Moonmilk speleothems of limestone caves host a rich microbiome, among which Actinobacteria represent one of the most abundant phyla. Ancient medical texts reported that moonmilk had therapeutical properties, thereby suggesting that its filamentous endemic actinobacterial population might be a source of natural products useful in human treatment. In this work, a screening approach was undertaken in order to isolate cultivable Actinobacteria from moonmilk of the Grotte des Collemboles in Belgium, to evaluate their taxonomic profile, and to assess their potential in biosynthesis of antimicrobials. Phylogenetic analysis revealed that all 78 isolates were exclusively affiliated to the genus and clustered into 31 distinct phylotypes displaying various pigmentation patterns and morphological features. Phylotype representatives were tested for antibacterial and antifungal activities and their genomes were mined for secondary metabolite biosynthetic genes coding for non-ribosomal peptide synthetases (NRPSs), and polyketide synthases (PKS). The moonmilk collection was found to display strong inhibitory activities against a wide range of reference organisms, as 94, 71, and 94% of the isolates inhibited or impaired the growth of Gram-positive, Gram-negative bacteria, and fungi, respectively. Interestingly, 90% of the cave strains induced strong growth suppression against the multi-drug resistant , a causative agent of invasive mycosis in cystic fibrosis and chronic granulomatous diseases. No correlation was observed between the global antimicrobial activity of an individual strain and the number of NRPS and PKS genes predicted in its genome, suggesting that approaches for awakening cryptic metabolites biosynthesis should be applied to isolates with no antimicrobial phenotype. Overall, our work supports the common belief that moonmilk might effectively treat various infectious diseases thanks to the presence of a highly diverse population of prolific antimicrobial producing , and thus may indeed constitute a promising reservoir of potentially novel active natural compounds.
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http://dx.doi.org/10.3389/fmicb.2016.01455DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5030222PMC
September 2016

Coding and noncoding variants in HFM1, MLH3, MSH4, MSH5, RNF212, and RNF212B affect recombination rate in cattle.

Genome Res 2016 10 11;26(10):1323-1332. Epub 2016 Aug 11.

Unit of Animal Genomics, GIGA-R & Faculty of Veterinary Medicine, University of Liège (B34), 4000 Liège, Belgium.

We herein study genetic recombination in three cattle populations from France, New Zealand, and the Netherlands. We identify 2,395,177 crossover (CO) events in 94,516 male gametes, and 579,996 CO events in 25,332 female gametes. The average number of COs was found to be larger in males (23.3) than in females (21.4). The heritability of global recombination rate (GRR) was estimated at 0.13 in males and 0.08 in females, with a genetic correlation of 0.66 indicating that shared variants are influencing GRR in both sexes. A genome-wide association study identified seven quantitative trait loci (QTL) for GRR. Fine-mapping following sequence-based imputation in 14,401 animals pinpointed likely causative coding (5) and noncoding (1) variants in genes known to be involved in meiotic recombination (HFM1, MSH4, RNF212, MLH3, MSH5) for 5/7 QTL, and noncoding variants (3) in RNF212B for 1/7 QTL. This suggests that this RNF212 paralog might also be involved in recombination. Most of the identified mutations had significant effects in both sexes, with three of them each accounting for ∼10% of the genetic variance in males.
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http://dx.doi.org/10.1101/gr.204214.116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5052053PMC
October 2016

On the use of high-throughput sequencing for the study of cyanobacterial diversity in Antarctic aquatic mats.

J Phycol 2016 06 27;52(3):356-68. Epub 2016 Apr 27.

Centre for Protein Engineering, University of Liège, Allée du Six Août 13, B6a, Quartier Agora, Sart-Tilman, 4000, Liège, Belgium.

The study of Antarctic cyanobacterial diversity has been mostly limited to morphological identification and traditional molecular techniques. High-throughput sequencing (HTS) allows a much better understanding of microbial distribution in the environment, but its application is hampered by several methodological and analytical challenges. In this work, we explored the use of HTS as a tool for the study of cyanobacterial diversity in Antarctic aquatic mats. Our results highlight the importance of using artificial communities to validate the parameters of the bioinformatics procedure used to analyze natural communities, since pipeline-dependent biases had a strong effect on the observed community structures. Analysis of microbial mats from five Antarctic lakes and an aquatic biofilm from the Sub-Antarctic showed that HTS is a valuable tool for the assessment of cyanobacterial diversity. The majority of the operational taxonomic units retrieved were related to filamentous taxa such as Leptolyngbya and Phormidium, which are common genera in Antarctic lacustrine microbial mats. However, other phylotypes related to different taxa such as Geitlerinema, Pseudanabaena, Synechococcus, Chamaesiphon, Calothrix, and Coleodesmium were also found. Results revealed a much higher diversity than what had been reported using traditional methods and also highlighted remarkable differences between the cyanobacterial communities of the studied lakes. The aquatic biofilm from the Sub-Antarctic had a distinct cyanobacterial community from the Antarctic lakes, which in turn displayed a salinity-dependent community structure at the phylotype level.
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http://dx.doi.org/10.1111/jpy.12399DOI Listing
June 2016

Rooting the tree of life: the phylogenetic jury is still out.

Philos Trans R Soc Lond B Biol Sci 2015 Sep;370(1678):20140329

Centre for Biodiversity Theory and Modelling, USR CNRS 2936, Station d'Ecologie Expérimentale du CNRS, Moulis 09200, France Département de Biochimie, Centre Robert-Cedergren, Université de Montréal, Montréal, Quebec, Canada H3C 3J7

This article aims to shed light on difficulties in rooting the tree of life (ToL) and to explore the (sociological) reasons underlying the limited interest in accurately addressing this fundamental issue. First, we briefly review the difficulties plaguing phylogenetic inference and the ways to improve the modelling of the substitution process, which is highly heterogeneous, both across sites and over time. We further observe that enriched taxon samplings, better gene samplings and clever data removal strategies have led to numerous revisions of the ToL, and that these improved shallow phylogenies nearly always relocate simple organisms higher in the ToL provided that long-branch attraction artefacts are kept at bay. Then, we note that, despite the flood of genomic data available since 2000, there has been a surprisingly low interest in inferring the root of the ToL. Furthermore, the rare studies dealing with this question were almost always based on methods dating from the 1990s that have been shown to be inaccurate for much more shallow issues! This leads us to argue that the current consensus about a bacterial root for the ToL can be traced back to the prejudice of Aristotle's Great Chain of Beings, in which simple organisms are ancestors of more complex life forms. Finally, we demonstrate that even the best models cannot yet handle the complexity of the evolutionary process encountered both at shallow depth, when the outgroup is too distant, and at the level of the inter-domain relationships. Altogether, we conclude that the commonly accepted bacterial root is still unproven and that the root of the ToL should be revisited using phylogenomic supermatrices to ensure that new evidence for eukaryogenesis, such as the recently described Lokiarcheota, is interpreted in a sound phylogenetic framework.
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http://dx.doi.org/10.1098/rstb.2014.0329DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4571568PMC
September 2015

Origin and evolution of metal P-type ATPases in Plantae (Archaeplastida).

Front Plant Sci 2013 7;4:544. Epub 2014 Jan 7.

PhytoSYSTEMS, University of Liège Liège, Belgium ; Eukaryotic Phylogenomics, Department of Life Sciences, University of Liège Liège, Belgium.

Metal ATPases are a subfamily of P-type ATPases involved in the transport of metal cations across biological membranes. They all share an architecture featuring eight transmembrane domains in pairs of two and are found in prokaryotes as well as in a variety of Eukaryotes. In Arabidopsis thaliana, eight metal P-type ATPases have been described, four being specific to copper transport and four displaying a broader metal specificity, including zinc, cadmium, and possibly copper and calcium. So far, few efforts have been devoted to elucidating the origin and evolution of these proteins in Eukaryotes. In this work, we use large-scale phylogenetics to show that metal P-type ATPases form a homogenous group among P-type ATPases and that their specialization into either monovalent (Cu) or divalent (Zn, Cd…) metal transport stems from a gene duplication that took place early in the evolution of Life. Then, we demonstrate that the four subgroups of plant metal ATPases all have a different evolutionary origin and a specific taxonomic distribution, only one tracing back to the cyanobacterial progenitor of the chloroplast. Finally, we examine the subsequent evolution of these proteins in green plants and conclude that the genes thoroughly characterized in model organisms are often the result of lineage-specific gene duplications, which calls for caution when attempting to infer function from sequence similarity alone in non-model organisms.
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http://dx.doi.org/10.3389/fpls.2013.00544DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3922081PMC
February 2014

Chromera velia, endosymbioses and the rhodoplex hypothesis--plastid evolution in cryptophytes, alveolates, stramenopiles, and haptophytes (CASH lineages).

Genome Biol Evol 2014 Mar;6(3):666-84

Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH, Braunschweig, Germany.

The discovery of Chromera velia, a free-living photosynthetic relative of apicomplexan pathogens, has provided an unexpected opportunity to study the algal ancestry of malaria parasites. In this work, we compared the molecular footprints of a eukaryote-to-eukaryote endosymbiosis in C. velia to their equivalents in peridinin-containing dinoflagellates (PCD) to reevaluate recent claims in favor of a common ancestry of their plastids. To this end, we established the draft genome and a set of full-length cDNA sequences from C. velia via next-generation sequencing. We documented the presence of a single coxI gene in the mitochondrial genome, which thus represents the genetically most reduced aerobic organelle identified so far, but focused our analyses on five "lucky genes" of the Calvin cycle. These were selected because of their known support for a common origin of complex plastids from cryptophytes, alveolates (represented by PCDs), stramenopiles, and haptophytes (CASH) via a single secondary endosymbiosis with a red alga. As expected, our broadly sampled phylogenies of the nuclear-encoded Calvin cycle markers support a rhodophycean origin for the complex plastid of Chromera. However, they also suggest an independent origin of apicomplexan and dinophycean (PCD) plastids via two eukaryote-to-eukaryote endosymbioses. Although at odds with the current view of a common photosynthetic ancestry for alveolates, this conclusion is nonetheless in line with the deviant plastome architecture in dinoflagellates and the morphological paradox of four versus three plastid membranes in the respective lineages. Further support for independent endosymbioses is provided by analysis of five additional markers, four of them involved in the plastid protein import machinery. Finally, we introduce the "rhodoplex hypothesis" as a convenient way to designate evolutionary scenarios where CASH plastids are ultimately the product of a single secondary endosymbiosis with a red alga but were subsequently horizontally spread via higher-order eukaryote-to-eukaryote endosymbioses.
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http://dx.doi.org/10.1093/gbe/evu043DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3971594PMC
March 2014

The mitochondrial respiratory chain of the secondary green alga Euglena gracilis shares many additional subunits with parasitic Trypanosomatidae.

Mitochondrion 2014 Nov 21;19 Pt B:338-49. Epub 2014 Feb 21.

Genetics and Physiology of Microalgae, Department of Life Sciences, University of Liège, B-4000 Liège, Belgium; PhytoSYSTEMS, University of Liège, B-4000 Liège, Belgium. Electronic address:

The mitochondrion is an essential organelle for the production of cellular ATP in most eukaryotic cells. It is extensively studied, including in parasitic organisms such as trypanosomes, as a potential therapeutic target. Recently, numerous additional subunits of the respiratory-chain complexes have been described in Trypanosoma brucei and Trypanosoma cruzi. Since these subunits had apparently no counterparts in other organisms, they were interpreted as potentially associated with the parasitic trypanosome lifestyle. Here we used two complementary approaches to characterise the subunit composition of respiratory complexes in Euglena gracilis, a non-parasitic secondary green alga related to trypanosomes. First, we developed a phylogenetic pipeline aimed at mining sequence databases for identifying homologues to known respiratory-complex subunits with high confidence. Second, we used MS/MS proteomics after two-dimensional separation of the respiratory complexes by Blue Native- and SDS-PAGE both to confirm in silico predictions and to identify further additional subunits. Altogether, we identified 41 subunits that are restricted to E. gracilis, T. brucei and T. cruzi, along with 48 classical subunits described in other eukaryotes (i.e. plants, mammals and fungi). This moreover demonstrates that at least half of the subunits recently reported in T. brucei and T. cruzi are actually not specific to Trypanosomatidae, but extend at least to other Euglenozoa, and that their origin and function are thus not specifically associated with the parasitic lifestyle. Furthermore, preliminary biochemical analyses suggest that some of these additional subunits underlie the peculiarities of the respiratory chain observed in Euglenozoa.
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http://dx.doi.org/10.1016/j.mito.2014.02.001DOI Listing
November 2014

The African coelacanth genome provides insights into tetrapod evolution.

Nature 2013 Apr;496(7445):311-6

Molecular Genetics Program, Benaroya Research Institute, Seattle, Washington 98101, USA.

The discovery of a living coelacanth specimen in 1938 was remarkable, as this lineage of lobe-finned fish was thought to have become extinct 70 million years ago. The modern coelacanth looks remarkably similar to many of its ancient relatives, and its evolutionary proximity to our own fish ancestors provides a glimpse of the fish that first walked on land. Here we report the genome sequence of the African coelacanth, Latimeria chalumnae. Through a phylogenomic analysis, we conclude that the lungfish, and not the coelacanth, is the closest living relative of tetrapods. Coelacanth protein-coding genes are significantly more slowly evolving than those of tetrapods, unlike other genomic features. Analyses of changes in genes and regulatory elements during the vertebrate adaptation to land highlight genes involved in immunity, nitrogen excretion and the development of fins, tail, ear, eye, brain and olfaction. Functional assays of enhancers involved in the fin-to-limb transition and in the emergence of extra-embryonic tissues show the importance of the coelacanth genome as a blueprint for understanding tetrapod evolution.
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http://dx.doi.org/10.1038/nature12027DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3633110PMC
April 2013

Impact of missing data on phylogenies inferred from empirical phylogenomic data sets.

Mol Biol Evol 2013 Jan 28;30(1):197-214. Epub 2012 Aug 28.

Département de Biochimie, Centre Robert-Cedergren, Université de Montréal, Montréal, Québec, Canada.

Progress in sequencing technology allows researchers to assemble ever-larger supermatrices for phylogenomic inference. However, current phylogenomic studies often rest on patchy data sets, with some having 80% missing (or ambiguous) data or more. Though early simulations had suggested that missing data per se do not harm phylogenetic inference when using sufficiently large data sets, Lemmon et al. (Lemmon AR, Brown JM, Stanger-Hall K, Lemmon EM. 2009. The effect of ambiguous data on phylogenetic estimates obtained by maximum likelihood and Bayesian inference. Syst Biol. 58:130-145.) have recently cast doubt on this consensus in a study based on the introduction of parsimony-uninformative incomplete characters. In this work, we empirically reassess the issue of missing data in phylogenomics while exploring possible interactions with the model of sequence evolution. First, we note that parsimony-uninformative incomplete characters are actually informative in a probabilistic framework. A reanalysis of Lemmon's data set with this in mind gives a very different interpretation of their results and shows that some of their conclusions may be unfounded. Second, we investigate the effect of the progressive introduction of missing data in a complete supermatrix (126 genes × 39 species) capable of resolving animal relationships. These analyses demonstrate that missing data perturb phylogenetic inference slightly beyond the expected decrease in resolving power. In particular, they exacerbate systematic errors by reducing the number of species effectively available for the detection of multiple substitutions. Consequently, large sparse supermatrices are more sensitive to phylogenetic artifacts than smaller but less incomplete data sets, which argue for experimental designs aimed at collecting a modest number (~50) of highly covered genes. Our results further confirm that including incomplete yet short-branch taxa (i.e., slowly evolving species or close outgroups) can help to eschew artifacts, as predicted by simulations. Finally, it appears that selecting an adequate model of sequence evolution (e.g., the site-heterogeneous CAT model instead of the site-homogeneous WAG model) is more beneficial to phylogenetic accuracy than reducing the level of missing data.
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http://dx.doi.org/10.1093/molbev/mss208DOI Listing
January 2013

A single ancient origin for prototypical serine/arginine-rich splicing factors.

Plant Physiol 2012 Feb 12;158(2):546-60. Epub 2011 Dec 12.

Laboratory of Functional Genomics and Plant Molecular Imaging and Centre for Assistance in Technology of Microscopy, Department of Life Sciences, Institute of Botany, University of Liège, B-4000 Liege, Belgium.

Eukaryotic precursor mRNA splicing is a process involving a very complex RNA-protein edifice. Serine/arginine-rich (SR) proteins play essential roles in precursor mRNA constitutive and alternative splicing and have been suggested to be crucial in plant-specific forms of developmental regulation and environmental adaptation. Despite their functional importance, little is known about their origin and evolutionary history. SR splicing factors have a modular organization featuring at least one RNA recognition motif (RRM) domain and a carboxyl-terminal region enriched in serine/arginine dipeptides. To investigate the evolution of SR proteins, we infer phylogenies for more than 12,000 RRM domains representing more than 200 broadly sampled organisms. Our analyses reveal that the RRM domain is not restricted to eukaryotes and that all prototypical SR proteins share a single ancient origin, including the plant-specific SR45 protein. Based on these findings, we propose a scenario for their diversification into four natural families, each corresponding to a main SR architecture, and a dozen subfamilies, of which we profile both sequence conservation and composition. Finally, using operational criteria for computational discovery and classification, we catalog SR proteins in 20 model organisms, with a focus on green algae and land plants. Altogether, our study confirms the homogeneity and antiquity of SR splicing factors while establishing robust phylogenetic relationships between animal and plant proteins, which should enable functional analyses of lesser characterized SR family members, especially in green plants.
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http://dx.doi.org/10.1104/pp.111.189019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3271749PMC
February 2012

Variants modulating the expression of a chromosome domain encompassing PLAG1 influence bovine stature.

Nat Genet 2011 May 24;43(5):405-13. Epub 2011 Apr 24.

Unit of Animal Genomics, Interdisciplinary Institute of Applied Genomics (GIGA-R) and Faculty of Veterinary Medicine, University of Liège (B34), Liège, Belgium.

We report mapping of a quantitative trait locus (QTL) with a major effect on bovine stature to a ∼780-kb interval using a Hidden Markov Model-based approach that simultaneously exploits linkage and linkage disequilibrium. We re-sequenced the interval in six sires with known QTL genotype and identified 13 clustered candidate quantitative trait nucleotides (QTNs) out of >9,572 discovered variants. We eliminated five candidate QTNs by studying the phenotypic effect of a recombinant haplotype identified in a breed diversity panel. We show that the QTL influences fetal expression of seven of the nine genes mapping to the ∼780-kb interval. We further show that two of the eight candidate QTNs, mapping to the PLAG1-CHCHD7 intergenic region, influence bidirectional promoter strength and affect binding of nuclear factors. By performing expression QTL analyses, we identified a splice site variant in CHCHD7 and exploited this naturally occurring null allele to exclude CHCHD7 as single causative gene.
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http://dx.doi.org/10.1038/ng.814DOI Listing
May 2011