Biology subjects

Coomer-Blundell, A.

Publications and source records attributed to Coomer-Blundell, A..

3 recordsLinked to original sources

bioRxiv2026

Resistance Breaking in Root-knot Nematodes Carries a Fitness Cost Associated with Defective Feeding Site Development

Root-knot nematodes (RKNs) cause an estimated 157 billion dollars in annual yield losses worldwide. In tomato, resistance to RKNs is conferred by the single dominant resistance gene Mi-1, which has been widely integrated into commercial cultivars. Prolonged and widespread use of Mi-1 has led to the emergence of resistance-breaking populations in tomato fields worldwide; however, the consequences of resistance breaking for nematode performance on susceptible hosts remain poorly understood. Here, we compared infection outcomes of two closely related strains of Meloidogyne javanica, VW4 (Mi-1-avirulent; wild-type) and VW5 (Mi-1-virulent; resistance-breaking), on three susceptible hosts: tomato, cucumber, and rice. Across all hosts, VW5 produced significantly fewer eggs than VW4, revealing a fitness cost associated with Mi-1 virulence. Light and transmission electron microscopy of tomato and cucumber galls revealed impaired feeding site establishment by VW5. Consistent with these observations, transcriptomic profiling showed that VW5 infection induced weaker host transcriptional reprogramming and lacked gene expression signatures associated with effective suppression of plant defense responses. Together, these findings demonstrate that adaptation to Mi-1-mediated resistance incurs a fitness cost on susceptible plants and is accompanied by impaired feeding site formation and altered host reprogramming. Furthermore, these results establish VW4 and VW5 as a powerful resource for understanding nematode genes and pathways required for successful parasitism and feeding site development.

plant biology↗

bioRxiv2025

A Chromosome-scale Reference Genome of Meloidogyne hapla reveals localized recombination hotspots enriched with Effector Proteins

Root-knot nematodes (Meloidogyne spp.) are among the most destructive agricultural pests that cause significant yield losses across a wide range of crops. Meloidogyne hapla, a diploid species, is a valuable model for studying root-knot nematodes due to its parasitic diversity, small genome, and a reproductive strategy that facilitates genetic analysis. Here, we present a high-quality chromosome-scale assembly of M. hapla, generated using multiple sequencing platforms-PacBio HiFi, ONT, Illumina and HiC. The 59 Mb assembly comprises 16 chromosome-length scaffolds, notably lacking canonical telomeric repeats. Instead, we identified a tandem 16-mer repeat mainly present at scaffold ends, suggesting an alternative system for chromosome-end maintenance. Genetic linkage analysis of F2 populations derived from crosses between M. hapla strains validated the assembly but also revealed anomalies indicating chromosome structure differences between parental isolates such as fissions, fusions, and rearrangements. This analysis also revealed sharply delineated zones of high recombination on most chromosome arms. We also identified 1,258 genes encoding putative secreted proteins (PSP), which should be enriched in genes involved in host interaction and pathogenicity. Most of the PSP genes had orthologs in other plant parasitic nematode species, and the majority were pioneers, lacking known functional domains. Notably, we found that PSPs are significantly enriched in high-recombination zones, possibly facilitating their rapid evolution. Overall, our study provides new insights into the genome structure of diploid root-knot nematodes and highlights the interplay between genome architecture, recombination, and parasitism. These findings raise new questions about how genetic and genomic adaptations drive the success of rootknot nematodes as plant parasites.

plant biology↗

bioRxiv2023

Phased chromosome-scale genome assembly of an asexual, allopolyploid root-knot nematode reveals complex subgenomic structure

We present the chromosome-scale genome of the allopolyploid root-knot nematode Meloidogyne javanica. We show that the M. javanica genome is predominantly allotetraploid, comprising two subgenomes, A and B, that most likely originated from hybridisation of two ancestral parental species. The assembly is annotated using full-length non-chimeric transcripts, comparison to reference databases, and ab initio prediction techniques, and the subgenomes are phased using ancestral k-mer spectral analysis. Subgenome B appears to show greater fission of chromosomal contigs, and while there is substantial synteny between subgenomes, we also identify regions lacking synteny that may have diverged in the ancestral genomes prior to or following hybridisation. Indels are common both between alleles within a subgenome, and between the A and B subgenomes, suggesting the M. javanica genome exists in a dynamic hypo-tetraploidy where copy number can vary along the chromosome. This annotated and phased genome assembly forms a significant resource for understanding the origins and genetics of these globally important plant pathogens. Author SummaryRoot-knot nematodes represent one of the most significant crop parasites globally. Despite their agricultural importance, only rudimentary genomic resources have been published to date, leaving a gap in the understanding of genetic mechanisms driving genome evolution and crop virulence. Here, we have used modern genomic and bioinformatic approaches to create a chromosome-scale reference genome to investigate the origins and genomic constitution of the root-knot nematode species Meloidogyne javanica. This species reproduces by ameiotic parthenogenesis and has an allopolyploid genome and is among the most damaging plant parasitic nematodes with a large and evolving plant host range. Utilising modern long-range DNA sequencing and bioinformatics approaches, we successfully phased the genome into its constituent subgenomes, a first for this agriculturally important clade. While we find the genomic landscape is mostly syntenic between subgenomes, we identified regions of minimal similarity, and highlight structural divergence between subgenomes. We demonstrate that this species was originally tetraploid, but insertions and deletions have been the major force in generating diversity, resulting in a hypo-tetraploid genome with local variations in ploidy.

genomics↗