Biology subjects

Rouard, M.

Publications and source records attributed to Rouard, M..

11 recordsLinked to original sources

bioRxiv2026

SaVanache: indexing and visualizing pangenome variation graphs

With the rapid increase in genome sequencing and the growing availability of genomic resources, genomics is shifting toward pangenome representations that capture intra- and inter-specific diversity by integrating multiple genomes into a single entity. These pangenomes are increasingly modeled as graphs, encoding complex genomic variations in structures such as de Bruijn or variation graphs. However, while genome browsers provide standard and effective solutions for visualizing single or limited numbers of genomes, equivalent interactive tools for graph-based pangenomes remain limited, particularly for variation graph models. We developed SaVanache, a multi-resolution visualization interface designed to explore pangenome variation graphs at various depths. SaVanache enables the exploration of both global diversity and structural variations (SVs) across genomes relative to a user-defined linear pivot genome. Unlike synteny viewers, SaVanache emphasizes variations by representing SV types through a dedicated set of glyphs, facilitating intuitive one-to-many comparisons. To support smooth exploration, SaVanache preprocesses a Graphical Fragment Assembly (GFA) pangenome file into optimized index and data structures, enabling fast, real-time queries on large pangenome graphs. By combining advanced visualization techniques with efficient data handling, SaVanache provides a robust tool for scientists to analyze and visualize genetic variation within genomes and pangenomes, facilitating the identification of genetic determinants associated with phenotypes of interest and fully exploiting current genomic resources. Author summaryWe introduce SaVanache, an innovative tool that transforms the way we explore genomic resources. SaVanache allows visualization and analysis of pangenome variation graphs (PVGs), which capture genomic diversity by integrating structural variants (SV) and single nucleotide polymorphisms (SNPs) across multiple genomes. Unlike traditional genome browsers limited to a few genomes, SaVanache offers a multi-level, user-friendly interface that allows users to explore from whole pangenomes down to individual structural variants, enabling multidimensional research and development. Using a linear pivot genome as a visual reference, SaVanache simplifies complex PVG structures into intuitive comparisons. It efficiently handles large datasets and speeds up data retrieval through internal parsing. The front-end, built with modern JavaScript frameworks, provides interactive and responsive visualization, while the Python/Django backend supports real-time data updates. Users can detect and classify SVs by comparing syntenic segments between genomes, visualized through a novel glyph-based system that uses shapes and colors to represent complex rearrangements. SaVanache supports seamless zooming from chromosome-wide to nucleotide-level views, interactive diversity scatterplots, dynamic pivot genome switching, and grouping genomes by metadata to explore genotype-phenotype links. In addition, export functions bridge visualization with downstream bioinformatics. Developed with user feedback, SaVanache balances biological relevance and computational efficiency, overcoming PVG complexity to empower users with unprecedented insight into genomic diversity and SVs.

bioinformatics↗

bioRxiv2026

Ancestral Musaceae karyotype reconstruction provides insights into chromosome evolution and bract coloration

The banana family (Musaceae) exhibits remarkable diversity in both karyotype structure and bract coloration, yet the evolutionary dynamics of chromosomes and the genomic and regulatory basis underlying color diversification remain poorly understood. Here, we present a telomere-to-telomere (T2T), gap-free genome assembly of Musa exotica, an ornamental species with brightly colored bracts occupying an early-branching lineage within sect. Callimusa (Musa L.). By integrating this high-quality genome with other available Musaceae genomes, we reconstruct the ancestral Musaceae karyotype (AMK) for the first time, inferring a haploid chromosome number of n = 17. Comparative genomic analyses reveal recurrent, highly complex lineage-specific inter-chromosome rearrangements across extant Musaceae lineages, leading to inferred stepwise reductions in chromosome number to n = 11, 10, and 9. Notably, closely related species share similar rearrangement patterns, suggesting conserved evolutionary trajectories shaped by lineage-specific structural remodeling. Strikingly, rearrangement-associated regions are enriched for functionally important genes, particularly structural genes (CHS and F3H) and regulatory transcription factors (MYB and bHLH) involved in the anthocyanin biosynthesis pathway. Integrative transcriptomic and regulatory analyses further demonstrate coordinated activation of anthocyanin biosynthetic genes (CHS, CHI, F3'5'H, and ANS) in bracts, with expression divergence largely decoupled from gene dosage and predominantly driven by transcriptional regulation. Co-expression analyses reveal extensive MYB- and bHLH-enzyme interactions, underscoring their central role in modulating pathway activity and bract coloration diversity. Collectively, our findings suggest a link between genome structural evolution to trait diversification, offering a refined framework for understanding genome evolution and phenotypic diversification in Musaceae and other monocots. SignificanceWe reconstructed the ancestral Musaceae karyotype and revealed extensive lineage-specific chromosome rearrangements underlying karyotype evolution. Rearrangement-associated regions are enriched for anthocyanin biosynthetic and regulatory genes, suggesting that genome structural evolution may have contributed to bract coloration diversification in Musaceae. Integrative transcriptomic analyses further indicate that variation in anthocyanin-mediated bract coloration is more closely associated with transcriptional regulation than with gene dosage alone.

evolutionary biology↗

bioRxiv2024

Painting the diversity of a world's favourite fruit: A next generation catalogue of cultivated bananas

Societal impact statementBananas are nutritious fruits of major importance in the tropics and subtropics. Characterizing their diversity is essential to ensure their conservation and use. A catalogue showcasing cultivated bananas genomic diversity was compiled and is to be used as a tool to support the classification of banana cultivars. This research revealed that cultivated banana groups are not all made of identical clones. Materials from recent collecting missions indicated that more banana diversity is expected to be found as the exploration of the banana gene pool continues. These discoveries will drive dynamic conservation strategies for banana genetic resources and will increase their use. SummaryO_LIBanana is an important food crop cultivated in many tropical and subtropical regions around the world. Due to their low fertility, banana landraces are clonally propagated. However, different factors, such as synonymy and the effects of environment, make their assignment to described sets of clones, or cultivar groups, difficult. Consequently, passport data of accessions in genebanks is often uncomplete and sometimes inaccurate. C_LIO_LIWith the recent advances in genomics, a new powerful tool was developed enabling the fine-scale characterization of bananas ancestry along chromosomes, i.e. in silico chromosome painting. We applied this method to a high-throughput genotyping data set obtained from 317 banana accessions spanning most of the known cultivar groups. This set included both genebank and new uncharacterized materials. C_LIO_LIBy comparing curated morphological assignation to the genomic patterns resulting from in silico chromosome painting, we were able to compile a catalogue referencing the chromosome painting patterns of most of the described cultivar groups. C_LIO_LIExamining the genomic patterns obtained, we discovered intra-cultivar group variability. In some cultivar groups, mitotic recombination or deletions were clonally accumulated in cultivars. In addition, we identified at least 4 cultivar groups in which cultivars likely resulting from distinct sexual events co-existed, notably Pisang Awak in which 5 distinct genomic patterns of two ploidy levels were identified. New patterns were also discovered in the newest materials of the set, showing that a wider diversity of clones still exist on farm. C_LI

genomics↗

bioRxiv2023

Pangenomic exploration of Theobroma cacao: new insights into gene content diversity and selection during domestication

The Cacao tree (Theobroma cacao L.) is a major cash crop and an important source of income for millions of farmers across Africa, Asia and Latin America. However, cacao farmers and producing countries are facing multiple challenges including pest and disease management, sustainable production under threat of climate changes and diversification of cocoa flavor profiles. Addressing these challenging requires a deeper understanding of the existing genetic diversity of the species. Yet, very little is known about the intraspecific gene content variation. In this study, we used the genome of 216 accessions of T. cacao (including 185 newly re-sequenced) covering a broad genetic diversity of the species to construct the first pan-genome of the cacao tree. As a result, we predicted a total of 30,489 pan-genes, enriching the reference Criollo genome with 1,407 new genes. Our analysis revealed that only a small fraction of these genes (9.2%) is dispensable, being absent in some individuals. However, these genes could represent a valuable resource for breeding efforts aimed at improving disease resistance in the species. We used this new pangenome resource to gain insights into how diversification and domestication processes have influenced genomic variability within the species. Notably, we observed a significant loss of genes within the domesticated Criollo genetic group. Furthermore, we found evidences suggesting that domestication processes have had an impact on the vigor and disease tolerance of Criollo accessions. In summary, our research has contributed to a better understanding of the cacao trees genome diversity. These findings offer new avenues for biological discovery and breeding, ultimately addressing the challenges faced by cacao farmers and producing countries.

genomics↗

bioRxiv2022

Wheat Panache - a pangenome graph database representing presence/absence variation across 16 bread wheat genomes

Bread wheat is one of humanitys most important staple crops, characterized by a large and complex genome with a high level of gene presence/absence variation between cultivars, hampering genomic approaches for crop improvement. With the growing global population and the increasing impact of climate change on crop yield, there is an urgent need to apply genomic approaches to accelerate wheat breeding. With recent advances in DNA sequencing technology, a growing number of high-quality reference genomes are becoming available, reflecting the genetic content of a diverse range of cultivars. However, information on the presence or absence of genomic regions has been hard to visualize and interrogate due to the size of these genomes and the lack of suitable bioinformatics tools. To address this limitation, we have produced a wheat pangenome graph maintained within an online database to facilitate interrogation and comparison of wheat cultivar genomes. The database allows users to visualize regions of the pangenome to assess presence/absence variation between bread wheat genomes. Database URL: http://www.appliedbioinformatics.com.au/wheat_panache

bioinformatics↗

bioRxiv2021

A chromosome-level reference genome of Ensete glaucum gives insight into diversity, chromosomal and repetitive sequence evolution in the Musaceae

BackgroundEnsete glaucum (2n = 2x = 18) is a giant herbaceous monocotyledonous plant in the small Musaceae family along with banana (Musa). A high-quality reference genome sequence of E. glaucum offers a vital genomic resource for functional and evolutionary studies of Ensete, the Musaceae, and more widely in the Zingiberales. FindingsUsing a combination of Illumina and Oxford Nanopore Technologies (ONT) sequencing, genome-wide chromosome conformation capture (Hi-C), and RNA survey sequence, we report a high-quality assembly of the 481.5Mb genome with 9 pseudochromosomes and 36,836 genes (BUSCO 94.7%). A total of 55% of the genome is composed of repetitive sequences with LTR-retroelements (37%) and DNA transposons (7%) predominant. The 5S and 45S rDNA were each present at one locus, and the 5S rDNA had an exceptionally long monomer length of c.1,056 bp, contrasting with the c. 450 bp monomer at multiple loci in Musa. A tandemly repeated c. 134 bp satellite, 1.1% of the genome (with no similar sequence in Musa), was present around all nine centromeres, with a LINE retroelement also found at Musa centromeres. The assembly, including centromeric positions, enabled us to characterize in detail the chromosomal rearrangements occurring between the x = 9 species and x = 11 species of Musa. Only one chromosome has the same gene content as M. acuminata (ma). Three ma chromosomes represent part of only one E. glaucum (eg) chromosome, while the remaining seven ma chromosomes are fusions of parts of two, three, or four eg chromosomes, demonstrating complex and multiple evolutionary rearrangements in the change between x = 9 and x = 11. ConclusionsThe advance towards a Musaceae pangenome including E. glaucum, tolerant of extreme environments, makes a complete set of gene alleles available for crop breeding and understanding environmental responses. The chromosome-scale genome assembly show how chromosome number evolves, and features of the rapid evolution of repetitive sequences.

plant biology↗

bioRxiv2021

Phylogenetic analyses for orthogroup-based classification of GDSL-type esterase/lipase (GELP) family in angiosperms

GDSL-type esterase/lipase (GELP) enzymes have multiple functions in plants, spanning from developmental processes to the response to biotic and abiotic stresses. Genes encoding GELP belong to a large gene family with several tens to more than hundred members per angiosperm species. Here, we applied iterative phylogenetic analyses to identify 10 main clusters subdivided into 44 expert-curated reference orthogroups (OGs) using three monocot and five dicot genomes. Our results show that some GELP OGs expanded while others were maintained as single copy genes. This semi-automatic approach proves to be effective to characterize large gene families and provides a solid classification framework for the GELP members in angiosperms. The orthogroup-based reference will be useful to perform comparative studies, infer gene functions and better understand the evolutionary history of this gene family.

genomics↗

bioRxiv2021

Panache: a Web Browser-Based Viewer for Linearized Pangenomes

MotivationPangenomics evolved since its first applications on bacteria, extending from the study of genes for a given population to the study of all of its sequences available. While multiple methods are being developed to construct pangenomes in eukaryotic species there is still a gap for efficient and user-friendly visualization tools. Emerging graph representations comes with their own challenges, and linearity remains a suitable option for user-friendliness. ResultsWe introduce Panache, a tool for the visualization and exploration of linear representations of gene-based and sequence-based pangenomes. It uses a layout similar to genome browsers to display presence absence variations and additional tracks along a linear axis with a pangenomics perspective. AvailabilityPanache is available at github.com/SouthGreenPlatform/panache under the MIT License. Contacteloi.durant@ird.fr, m.rouard@cgiar.org

bioinformatics↗

bioRxiv2021

Wild to domesticates: genomes of edible diploid bananas hold traces of several undefined genepools

This study is an unprecedent exploration of the diversity of 226 diploid bananas genotyped with restriction-site-associated DNA sequencing data (RADseq) to clarify the processes that led to the creation of edible diploid AA bananas. This wide set included 72 seedy bananas, mostly M. acuminata from different genepools, and 154 edible, i.e. parthenocarpic and sterile, AA accessions obtained from genebanks and recent collecting missions. We highlighted the geographic organisation of the diversity of edible AAs and confirmed the admixed nature of many and further conducted introgressions tests within AAs from South East Asia and New Guinea. Lastly, taking advantage of the presence of an important number of M. acuminata ssp. banksii (22) and of AA from Papua New Guinea (76) in the set, we investigated the patterns of differentiation between wild and cultivated bananas seemingly belonging to the same genepool. We discovered a few cultivated AAs that may be of pure origins both in South-East Asia and in New Guinea. We also detected two undefined parental genepools in South East Asia for which regions of origin could be Thailand and a region between north Borneo and the Philippines, respectively. Finally, we suggest the existence of a third genepool in New Guinea island that might be a source population for both edible AAs and the local M. acuminata ssp. banksii.

plant biology↗

bioRxiv2019

Unraveling the complex story of intergenomic recombination in ABB allotriploid bananas

Background and AimsBananas (Musa spp.) are a major staple food for hundreds of millions of people in developing countries. The cultivated varieties are seedless and parthenocarpic clones of which the ancestral origin remains to be clarified. The most important cultivars are triploids with an AAA, AAB, or ABB genome constitution, with A and B genomes provided by M. acuminata and M. balbisiana, respectively. Previous studies suggested that inter-genome recombinations were relatively common in banana cultivars and that triploids were more likely to have passed through an intermediate hybrid. In this study, we investigated the chromosome structure within the ABB group, composed of starchy cooking bananas that play an important role in food security.\n\nMethodsUsing SNP markers called from RAD-Seq data, we studied the chromosome structure of 36 ABB genotypes spanning defined taxonomic subgroups. To complement our understanding, we search for similar events within nine AB hybrid genotypes.\n\nKey ResultsRecurrent Homoeologous Exchanges (HEs), i.e. chromatin exchanges between A and B subgenomes were unraveled with at least 9 founding events at the origin of the ABB bananas prior to the clonal diversification. The discovery of this nine founding events allows discussing the possible routes that led to the creation of the different subgroups and formulate new hypotheses. Based on our observations, we suggest different routes that gave rise to the current diversity in the ABB cultivars. Routes involving primary AB hybrids, routes leading to shared HEs and routes leading to a B excess ratio. Genetic fluxes took place between M. acuminata and M. balbisiana, particularly in India, where these unbalanced AB hybrids and ABB allotriploid originated and where cultivated M. balbisiana are abundant.\n\nConclusionsThe result of this study clarifies the classification of ABB cultivars and leading possibly to the revision of the classification of this subgroup. This is an important step to unravel the origin of polyploid bananas, and contributes to possible scenarios on the origin. ABB bananas are hypothesized to be more drought tolerant. Knowing the origin of our current cultivars and so their potential parents will help breeders to make the right choices for future crosses. The M. balbisiana genome is a good source to create new cultivars able to answer the numerous challenges of banana breeding.

genomics↗

bioRxiv2018

Three new genome assemblies support a rapid radiation in Musa acuminata (wild banana)

Edible bananas result from interspecific hybridization between Musa acuminata and Musa balbisiana, as well as among subspecies in M. acuminata. Four particular M. acuminata subspecies have been proposed as the main contributors of edible bananas, all of which radiated in a short period of time in southeastern Asia. Clarifying the evolution of these lineages at a whole-genome scale is therefore an important step toward understanding the domestication and diversification of this crop. This study reports the de novo genome assembly and gene annotation of a representative genotype from three different subspecies of M. acuminata. These data are combined with the previously published genome of the fourth subspecies to investigate phylogenetic relationships and genome evolution. Analyses of shared and unique gene families reveal that the four subspecies are quite homogenous, with a core genome representing at least 50% of all genes and very few M. acuminata species-specific gene families. Multiple alignments indicate high sequence identity between homologous single copy-genes, supporting the close relationships of these lineages. Interestingly, phylogenomic analyses demonstrate high levels of gene tree discordance, due to both incomplete lineage sorting and introgression. This pattern suggests rapid radiation within Musa acuminata subspecies that occurred after the divergence with M. balbisiana. Introgression between M. a. ssp. malaccensis and M. a. ssp. burmannica was detected across a substantial portion of the genome, though multiple approaches to resolve the subspecies tree converged on the same topology. To support future evolutionary and functional analyses, we introduce the PanMusa database, which enables researchers to exploration of individual gene families and trees.

evolutionary biology↗