Biology subjects

Wolstenholme, A.

Publications and source records attributed to Wolstenholme, A..

3 recordsLinked to original sources

bioRxiv2025

Ghosts of symbionts past: The hidden history of the dynamic association between filarial nematodes and their Wolbachia endosymbionts

Many, but not all, parasitic filarial nematodes (Onchocercidae) carry intracellular, maternally-transmitted Wolbachia symbionts, and these alphaproteobacteria are targets for anti-filarial chemotherapeutic interventions for human disease. The symbionts of Onchocercidae derive from four of the major supergroups (C, D, F and J) defined within the genus Wolbachia. Using twenty-two whole genome sequences of filarial nematodes and genome sequences of their Wolbachia partners, we have explored the evolutionary history of the nematode-Wolbachia symbiosis. We screened the nuclear genome sequences of all the nematodes for nuclear Wolbachia transfers (NUWTs), fragments of the Wolbachia genome that have been integrated into the nuclear genome. Six species have no current Wolbachia infection. Setaria labiatopapillosa had no validated NUWTs and we interpret this to mean that this species was never infected with Wolbachia. In the other five species (Acanthocheilonema viteae, Cercopithifilaria (Ce.) johnstoni, Elaeophora elaphi, Loa (Lo.) loa and Onchocerca flexuosa) we found NUWTs, implying they have previously had and have now lost Wolbachia infections. For each NUWT locus, we identified the supergroup membership of the Wolbachia from which it originated, and found that the five Wolbachia-free species carried NUWTs derived from multiple supergroups, including a high shared rate of sequences derived from supergroup C. In Dirofilaria repens we identified a sample that carried two Wolbachia symbionts, one from supergroup C and one from supergroup F. In Dirofilaria immitis where live infection with a supergroup C Wolbachia is found, we identified NUWTs derived from an F Wolbachia, confirming that the F association predated the divergence of these Dirofilaria species. The supergroup D lineage of Wolbachia, as present in the human parasites Wuchereria bancrofti and Brugia malayi, derives from a replacement event. Madathamugadia (Md.) hiepei shows signs of multiple recent repeated endosymbiont replacement. From these data we infer that the history of Wolbachia in onchocercid nematodes includes not only cospeciation (as present in the Onchocerca-Dirofilaria group in association with supergroup C Wolbachia) and loss (in the five Wolbachia-free species), but also frequent symbiont replacement and dual infection. This dynamic pattern is challenging to models that assume host-symbiont mutualism.

genomics↗

bioRxiv2023

The nuclear basket regulates distribution and mobility of nuclear pore complexes in budding yeast

Nuclear pore complexes (NPCs) mediate all traffic between the nucleus and the cytoplasm and are among the most stable protein assemblies in cells. Budding yeast cells carry two variants of NPCs which differ in the presence or absence of the nuclear basket proteins Mlp1, Mlp2 and Pml39. The binding of these basket proteins occurs very late in NPC assembly and Mlp-positive NPCs are excluded from the region of the nuclear envelope that borders the nucleolus. Here, we use recombination-induced tag exchange (RITE) to investigate the stability of all the NPC subcomplexes within individual NPCs. We show that the nuclear basket proteins Mlp1, Mlp2 and Pml39 remain stably associated with NPCs through multiple cell-division cycles, and that Mlp1/2 are responsible for the exclusion of NPCs from the nucleolar territory. In addition, we demonstrate that binding of the FG-nucleoporins Nup1 and Nup2 depletes also Mlp-negative NPCs from this region by an independent pathway. We develop a method for single NPC tracking in budding yeast and observe that NPCs exhibit increased mobility in the absence of nuclear basket components. Our data suggest that the distribution of NPCs on the nucleus is governed by multiple interaction of nuclear basket proteins with the nuclear interior. Significance StatementO_LIA subset of yeast nuclear pore complexes have a basket structure at their nuclear face. The stoichiometry, architecture and molecular functions of the basket are not clear. C_LIO_LIThe authors use a tag exchange method to show stable binding of nuclear basket proteins through multiple generations. They also find that multiple nuclear basket proteins disfavour localization of NPCs proximal to the nucleolus. C_LIO_LIThese findings demonstrate that having a nuclear basket is a final and stable state for yeast NPCs. The methods developed can be applied to gain more insight into the properties of NPCs and other stable complexes as they age. C_LI

cell biology↗

bioRxiv2023

Genome structure and population genomics of the canine heartworm Dirofilaria immitis

The heartworm, Dirofilaria immitis, is a filarial parasitic nematode responsible for significant morbidity and mortality in wild and domesticated canids. Resistance to macrocyclic lactone drug prevention represents a significant threat to parasite control and has prompted investigations to understand the genetic determinants of resistance. This study aimed to improve the genomic resources of D. immitis to enable a more precise understanding of how genetic variation is distributed within and between parasite populations worldwide, which will inform the likelihood and rate by which parasites, and in turn, resistant alleles, might spread. We have guided the scaffolding of a recently published genome assembly for D. immitis (ICBAS_JMDir_1.0) using the chromosomal-scale reference genomes of Brugia malayi and Onchocerca volvulus, resulting in an 89.5 Mb assembly composed of four autosomal- and one X-linked chromosomal-scale scaffolds representing 99.7% of the genome. Publicly available and new whole-genome sequencing data from 32 D. immitis samples from Australia, Italy and the USA were assessed using principal component analysis, nucleotide diversity (Pi) and absolute genetic divergence (Dxy) to characterise the global genetic structure and measure within- and between population diversity. These population genetic analyses revealed broad-scale genetic structure among globally diverse samples and differences in genetic diversity between populations; however, fine-scale subpopulation analysis was limited and biased by differences between sample types. Finally, we mapped SNPs previously associated with macrocyclic lactone resistance in the new genome assembly, revealing physical linkage of high-priority variants on chromosome 3, and determined their frequency in the studied populations. This new chromosomal assembly for D. immitis now allows for a more precise investigation of selection on genome-wide genetic variation and will enhance our understanding of parasite transmission and the spread of genetic variants responsible for resistance to treatment.

genomics↗