Biology subjects

McVey, A.

Publications and source records attributed to McVey, A..

5 recordsLinked to original sources

bioRxiv2026

Distinct modes of sequence evolution and epigenetic modifications underpin the origins of Starship-mediated variation in Pyricularia fungal plant pathogens

Fungal pathogens display remarkable variation in genome content and organization that directly impacts their survival and host interactions. Although numerous models have been proposed to explain the origins of this variation, they generally fail to explain or predict the mechanisms that generate the genome variation observed in natural populations. Starships are a recently discovered group of giant fungal transposons that carry dozens of genes as cargo and horizontally transfer both within and between species. Here, we identify the features of a newly defined "Starship compartment" in the major fungal plant pathogen Pyricularia oryzae. We test the hypothesis that the Starship compartment makes distinct contributions to fungal genome evolution by explicitly comparing its transferability, mutability, and epigenetic modifications with those of the canonical core and accessory compartments. To enable this, we developed an updated and user-friendly version of the annotation tool stargraph for the comprehensive annotation of Starships and Starship-like regions. Using this approach, we identified two distinct families of Starships and related Starship-like regions in P. oryzae that differ in their activity, impacts on genome organization, modes of sequence evolution, and epigenetic modifications. Elements from the more active family exhibit higher rates of structural variation than all other genomic compartments in the predominantly clonal isolates infecting rice. Both families of Starships encode specific suites of known effector sequences that contribute to plant disease and Starship activity accounts for avirulence gene turnover, which suggests that evolutionary change within the Starship compartment may subsequently impact the evolution of plant-fungal interactions. Starships from the more active family have repeatedly transferred across the Pyricularia genus and tend to be depleted in heterochromatic histone modifications and repeat-induced point mutations. However, contrasting histone modification profiles in this family suggests a genomic conflict between silencing or maintaining Starship activity. Our findings demonstrate that variation in the mode of sequence diversification and epigenetic modification within the Starship compartment underpins the impacts of these giant transposons on fungal genome evolution. We argue for the explicit consideration of not only the Starship compartment but of element-specific dynamics when investigating the evolution of host-fungal interactions.

genomics↗

bioRxiv2022

The rise and fall of SARS-CoV-2 variants and the emergence of competing Omicron lineages

In late December of 2019, high throughput sequencing technologies enabled rapid identification of SARS-CoV-2 as the etiological agent of COVID-19, and global sequencing efforts are now a critical tool for monitoring the ongoing spread and evolution of this virus. Here, we analyze a subset (n=83,204) of all publicly available SARS-CoV-2 genomes (n=~5.6 million) that were randomly selected, but equally distributed over the course of the pandemic. We plot the emergence and extinction of new variants of concern (VOCs) over time and show how this corresponds to the ongoing accumulation of mutations in SARS-CoV-2 genomes and individual proteins. While the accumulation of mutations generally follows a linear regression, non-synonymous mutations are significantly greater in Omicron viruses than in previous variants-especially in the spike and nucleoproteins-and these differences are more pronounced in a recently identified sub-lineage (BA.2) of Omicron. ImportanceOmicron is the fifth SARS-CoV-2 variant to be designated a Variant of Concern (VOC) by the World Health Organization (WHO). Here we provide a retrospective analysis of SARS-CoV-2 variants and explain how the Omicron variant is distinct. Our work shows that the spike and nucleoproteins have accumulated the most mutations in Omicron variants, but that the accessory proteins of SARS-CoV-2 sequences are changing most rapidly relative to their size. Collectively, this "Observation" provides a concise overview of SARS-CoV-2 evolution, reveals mutational differences between two Omicron lineages, and highlights changes in the SARS-CoV-2 proteome that have been under reported.

evolutionary biology↗

bioRxiv2021

The rise and fall of SARS-CoV-2 variants and the mutational profile of Omicron

In late December of 2019, high throughput sequencing technologies enabled rapid identification of SARS-CoV-2 as the etiological agent of COVID-19, and global sequencing efforts are now a critical tool for monitoring the ongoing spread and evolution of this virus. Here, we analyze a subset (n=87,032) of all publicly available SARS-CoV-2 genomes (n=[~]5.6 million) that were randomly selected, but equally distributed over the course of the pandemic. We plot the appearance of new variants of concern (VOCs) over time and show that the mutation rates in Omicron viruses are significantly greater than those in previously identified SARS-CoV-2 variants. Mutations in Omicron are primarily restricted to the spike protein, while 25 other viral proteins-- including those involved in SARS-CoV-2 replication--are highly conserved. Collectively, this suggests that the genetic distinction of Omicron primarily arose from selective pressures on the spike, and that the fidelity of replication of this variant has not been altered. ImportanceOmicron is the fifth SARS-CoV-2 variant to be designated a Variant of Concern (VOC) by the World Health Organization (WHO). Here we provide a retrospective analysis of SARS-CoV-2 variants and explain how the Omicron variant is distinct. Our work shows that the spike protein is a hotspot for viral evolution in all variants, suggesting that existing vaccines and diagnostics that target this protein may become less effective against Omicron and that our therapeutic and public health strategies will have to evolve along with the virus.

evolutionary biology↗

bioRxiv2021

Growth-dependent heterogeneity in the DNA damage response in Escherichia coli

In natural environments bacteria are frequently exposed to sub-lethal levels of DNA damage which leads to the induction of a stress response (the SOS response in Escherichia coli). Natural environments also vary in nutrient availability, resulting in distinct physiological changes in bacteria which may have direct implications on their capacity to repair their chromosomes. Here, we evaluated the impact of varying the nutrient availability on the expression of the SOS response induced by chronic sub-lethal DNA damage in E. coli. The expression of the SOS regulon was found to be highly heterogeneous at the single-cell level in all growth conditions. Surprisingly, we observed a larger fraction of high SOS-induced cells in slow growth as compared with fast growth, despite a higher rate of SOS induction in fast growth. This counter-intuitive result can be explained by the dynamic balance between the rate of SOS induction and the division rates of cells exposed to DNA damage. Taken together, our data illustrates how cell division and physiology come together to produce growth-dependent heterogeneity in the DNA damage response.

cell biology↗

bioRxiv2017

Dynamic protein aggregation regulates bacterial dormancy depth critical for antibiotic tolerance

The ability of some bacteria within a population to tolerate antibiotic treatment is often attributed to prolonged bacterial infection1-3. Unlike antibiotic resistance, which generally results from genetic mutations or plasmid transfer4,5, antibiotic tolerance usually refers to the phenomenon that a subgroup of cells can survive high dose antibiotic treatment as a result of phenotypic heterogeneity6,7. Previous studies mainly associate antibiotic tolerance with cell dormancy, by hypothesizing that the lethal effects of antibiotics are disabled due to the extremely slow metabolic and proliferation rates in dormant bacteria 8,9. However, less is known about how surviving bacteria subsequently escape from the dormant state and resuscitate, which is equally important for disease recurrence. Here we monitored the process of bacterial antibiotic tolerance and regrowth at the single-cell level, and found that each individual survival cell shows different dormancy depth, which in return regulates whether and when it can resume growth after removal of antibiotic. The persister cells are considered to be in shallow dormancy depth, while the viable but non-culturable cells (VBNC cells) are in deep dormancy depth. We further implemented time-lapse fluorescent imaging and biochemical analysis to establish that dynamic endogenous protein aggregation is an important indicator of bacterial dormancy depth. For cells to leave the dormant state and resuscitate, clearance of cellular protein aggregates and recovery of proteostasis are required. Through additional mutagenesis studies, we found the ability to recruit functional DnaK-ClpB machineries, which facilitate protein disaggregation in an ATP-dependent manner, determines the timeline (whether and when) for bacterial regrowth. Better understanding of the key factors regulating bacterial regrowth after surviving antibiotic attack could lead to new therapeutic strategies for combating bacterial antibiotic tolerance.

microbiology↗