A BAC-guided haplotype assembly pipeline increases the resolution of the virus resistance locus CMD2 in cassava

Cornet, L.; Zaidi, S. S.-e.-A.; Li, J.; ngapout, Y.; Shakir, S.; Meunier, L.; callot, C.; marande, w.; Hanikenne, M.; Rombauts, S.; Van De Peer, Y.; Vanderschuren, H.

doi:10.1101/2023.10.19.563145

bioRxiv · 10.1101/2023.10.19.563145

A BAC-guided haplotype assembly pipeline increases the resolution of the virus resistance locus CMD2 in cassava

Cornet, L.·Zaidi, S. S.-e.-A.·Li, J.·ngapout, Y.·Shakir, S.·Meunier, L.·callot, C.·marande, w.·Hanikenne, M.·Rombauts, S.·Van De Peer, Y.·Vanderschuren, H.

View original source ↗Export metadata ↓

Abstract

Cassava is an important crop for food security in the tropics where its production is jeopardized by several viral diseases, including the cassava mosaic disease (CMD) which is endemic in Sub-Saharan Africa and the Indian subcontinent. Resistance to CMD is linked to a single dominant locus, namely CMD2. The cassava genome contains highly repetitive regions making the accurate assembly of a reference genome challenging. In the present study, we generated BAC libraries of the CMD- susceptible cassava cultivar (cv.) 60444 and the CMD-resistant landrace TME3. We subsequently identified and sequenced BACs belonging to the CMD2 region in both cultivars using high-accuracy long-read PacBio circular consensus sequencing (ccs) reads. We then sequenced and assembled the complete genomes of cv. 60444 and TME3 using a combination of ONT ultra-long reads and optical mapping. Anchoring the assemblies on cassava genetic maps revealed discrepancies in our, as well as in previously released, CMD2 regions of the cv. 60444 and TME3 genomes. A BAC guided approach to assess cassava genome assemblies significantly improved the synteny between the assembled CMD2 regions of cv. 60444 and TME3 and the CMD2 genetic maps. We then performed repeat-unmasked gene annotation on CMD2 assemblies and identified 81 stress resistance proteins present in the CMD2 region, amongst which 31 were previously not reported in publicly available CMD2 sequences.

Explore related subjects

genomics Preprint

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Cornet, L., Zaidi, S. S.-e.-A., Li, J., ngapout, Y., Shakir, S., Meunier, L., callot, C., marande, w., Hanikenne, M., Rombauts, S., Van De Peer, Y., Vanderschuren, H.. 2023-10-19. A BAC-guided haplotype assembly pipeline increases the resolution of the virus resistance locus CMD2 in cassava. https://doi.org/10.1101/2023.10.19.563145

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

Contig-Resolved Genetic Context of Antimicrobial Resistome in Sediments of Two Contrasting Wastewater-Impacted Rivers

River sediments harbor diverse antimicrobial resistance (AMR) determinants; however, gene abundance alone provides limited insight into their genomic context, mobility potential, and associated bacterial hosts. This study employed an assembly- and read-mapping metagenomic framework to surface-sediment metagenomes (40.78 Gb clean data) from two contrasting wastewater-impacted Indian rivers, Adyar (Chennai) and Musi (Hyderabad), retaining sample-, contig- and open reading frame level provenance. ARG-carrying contigs (ACCs; n = 2,402) were annotated for mobile genetic elements (MGEs), biocide/metal resistance genes (BMRGs), virulence factor genes (VFGs), nitrogen-cycling genes (NCycGs), and putative host taxonomy. The resistomes exhibited substantial diversity (264 ARG subtypes) and spatial heterogeneity, with subtype richness in the Adyar (up to 171 subtypes) than in the Musi, where richness progressively declined downstream. Rank IV determinants dominated ARG abundance (77.82%), whereas Rank I determinants accounted for only 9.89%. MGEs were detected on just 3.12% (75/2,402) of ACCs, predominantly comprising plasmid-like contigs and proximal ARG-MGE associations. Co-occurrence with BMRGs was observed on 386 ACCs, whereas VFGs were uncommon (26 ACCs) and primarily represented dual-annotated efflux and envelope-integrity determinants rather than independent virulence loci. NCyc annotations were sparse (12 ACCs), with no evidence of complete nitrification or denitrification pathways. Taxonomic classification resolved 217 ACCs to the species level, with no matches to curated human pathogenic bacteria. Only two Acinetobacter-assigned ACCs exhibited both genus-level pathogenicity and mobility evidence. These findings highlight the importance of integrating mobility and host-taxonomic information to distinguish baseline environmental resistance from potential priorities for AMR surveillance.

genomics↗

bioRxiv2026

Time-resolved single-cell screening reveals the dynamic regulatory architecture of human cardiogenesis

Congenital heart disease (CHD) originates during early embryogenesis, yet when disease genes act cannot be determined from existing data. Human fetal heart atlases lack critical time points, and perturbation screens that systematically assess gene function currently profile at most a few time points. Here we combined single-cell CRISPR screening of 400 disease-relevant genes in cardioids, sampled daily over seven developmental days (~975,000 cells), with a matched multiome atlas. Perturbation phenotypes were strongly dependent on developmental stage. Perturbations that reshaped cell-fate allocation or gene expression were enriched for CHD-linked genes, and most acted already during progenitor stages. Timing was largely independent of the target gene's own expression, marking instead when a cell state became functionally dependent on it, and some effects persisted after expression declined. Consensus gene regulatory networks integrating perturbation and multiome data recovered stage-specific regulators and nominated HOXB2 and HOXB3 as candidate cardiac regulators. Many perturbations converged on shared downstream programmes, which were reorganised through differentiation. Effects correlated in progenitors were maintained in differentiated cells, split into distinct programmes, converged with other perturbations or disappeared entirely, indicating that gene function is highly context dependent. Beyond advancing our understanding of the developmental regulatory logic underlying CHD, our work provides a resource for developing context-dependent models for in silico prediction of perturbation effects.

genomics↗

bioRxiv2026

A Y-specific translocated gsdf copy is a candidate master sex-determining gene in common dab (Limanda limanda)

Sex-determining systems in flatfishes are highly diverse, and even closely related species can differ in both sex-determining loci and heterogametic systems. In common dab (Limanda limanda), the genetic basis of sex determination has not yet been established. Here, we investigated sex determination using pooled whole-genome sequencing combined with long-read genome sequencing of females and males from Iceland and Norway. Genome-wide allele-frequency analyses identified sex-associated regions consistent with male heterogamety (XX/XY), with the strongest signal on chromosome 16. Comparison of the existing reference assembly, which represents an X haplotype at this locus, with a haplotype-resolved male PacBio HiFi assembly revealed a [~]21.5 kb Y-specific insertion on chromosome 16. The insertion showed complete coverage in male pools but little or no coverage in female pools from either population. It contained a translocated genomic segment including a copy of gonadal soma-derived factor (gsdf) and a predicted gene of unknown function. Comparative genomic analyses were consistent with this segment originating from an autosomal gsdf-containing region on chromosome 1. Given the recurrent recruitment of gsdf as a sex-determining factor in teleosts, we designate the Y-linked copy gsdfY and identify it as the strongest candidate for the master sex-determining gene in common dab. Additional broad sex-associated differentiation on chromosome 19 was restricted to the Icelandic samples and may reflect population-specific expansion of the sex-linked region, although its structural basis remains unresolved. Together, these findings provide the first genomic characterization of sex determination in common dab and demonstrate how gene duplication and translocation can contribute to the evolution of novel sex-determining systems in flatfishes.

genomics↗