Biology subjects

Sikora, E.

Publications and source records attributed to Sikora, E..

3 recordsLinked to original sources

bioRxiv2024

Climatic fluctuations modulate eco-evolutionary processes associated with pathogen dynamics and continue to fuel bacterial spot epidemics in tomato

Recurring outbreaks caused by endemic pathogens continue to pose problems in managing plant, wildlife, livestock and human health. Understanding how these outbreaks unfold and what drives the variability in disease epidemics across space and time is less understood, especially in the agricultural settings. In this study, we investigated the contribution of pathogen genetic diversity, climatic variation and their interaction towards disease dynamics, with an integrative approach grounded on multitype, high resolution sequencing data and analysis techniques. This investigation was carried out for bacterial spot disease epidemic by surveying tomato fields for bacterial pathogen (Xanthomonas perforans) across southeastern US over a span of three years. The strength of epidemic severity varied across space and time in the agricultural fields. Disease severity was positively associated with strain diversity, and was linked to environmental fluctuations, specifically, large variation and extreme changes in certain climatic factors. Strain-resolved metagenomics approach revealed that co-existence of multiple pathogen lineages was common in the individual fields, although accompanied by differential lineage dynamics. The co-occurring lineages displayed environmentally dependent fitness contributions. By tracing allelic frequencies in pathogen populations across temporal scales, we find evidence for asynchronous allele cycling across seasons, hinting at the presence of adaptive single-nucleotide polymorphisms (SNPs) being polymorphic in space in response to seasonality. Despite this pathogen heterogeneity, we identified positively selected loci under parallel evolution, which may explain the nature of selection pressures experienced by the pathogen. While single pathogen lineage is assumed to dominate the host in the agricultural settings, our findings challenge this notion by demonstrating genetic diversity in the pathogen population observed within a single field and linking it to the disease dynamics. Our results explain the role of pathogen genetic diversity, climate-dependent compositional dynamics, and differential fitness contributions in dictating the variability of disease epidemics in the agricultural settings. Such findings will be invaluable for building predictive models in disease epidemiology. Our high-resolution combinatorial approach exploiting high- resolution sequence data, metadata types and analysis tools, is general enough to finely investigate disease epidemics at large scales in diverse case-studies concerning plant, animal and human health.

microbiology↗

bioRxiv2019

Cholesterol and matrisome pathways dysregulated in human APOE ε4 glia

Apolipoprotein E (APOE) {varepsilon}4 is the strongest genetic risk factor for Alzheimers disease (AD). Although its association with AD is well-established, the impact of APOE {varepsilon}4 on human brain cell function remains unclear. Here we investigated the effects of APOE {varepsilon}4 on several brain cell types derived from human induced pluripotent stem cells and human APOE targeted replacement mice. Gene set enrichment and pathway analyses of whole transcriptome profiles showed that APOE {varepsilon}4 is associated with dysregulation of cholesterol homeostasis in human but not mouse astrocytes and microglia. Elevated matrisome signaling associated with chemotaxis, glial activation and lipid biosynthesis in APOE {varepsilon}4 mixed neuron/astrocyte cultures parallels altered pathways uncovered in cell-type deconvoluted transcriptomic data from APOE {varepsilon}4 glia and AD post-mortem brains. Experimental validation of the transcriptomic findings showed that isogenic APOE {varepsilon}4 is associated with increased lysosomal cholesterol levels and decreased cholesterol efflux, demonstrating decoupled lipid metabolism. APOE {varepsilon}4 glia also secrete higher levels of proinflammatory chemokines, cytokines and growth factors, indicative of glial activation. Thus, APOE {varepsilon}4 induces human glia-specific dysregulation that may initiate AD risk.

neuroscience↗

bioRxiv2019

Recently emerged and diverse lineages of Xanthomonas perforans have independently evolved through plasmid acquisition and homologous recombination originating from multiple Xanthomonas species

Xanthomonas perforans is the predominant pathogen responsible for bacterial leaf spot of tomato and X. euvesicatoria of pepper in the southeast United States. Previous studies have indicated significant changes in the X. perforans population collected from Florida tomato fields over the span of two decades including a shift in race, diversification into three genetic groups, and host range expansion to pepper. Recombination originating from X. euvesicatoria was identified as the primary factor driving the diversification of X. perforans in Florida. The aim of this study was to genetically characterize X. perforans strains that were isolated from tomato and pepper plants grown in Alabama and compare them to the previously published genomes available from GenBank. Surprisingly, a maximum likelihood phylogeny coupled with a Bayesian analysis of population structure revealed the presence of two novel genetic groups in Alabama, which each harbored a different transcription activation-like effector (TALE). While one TALE, avrHah1, was associated with adaptation of X. perforans to pepper, the other was identified as a new class within the avrBs3 family, designated here as pthXp1. Examination of patterns of homologous recombination between X. perforans and other closely related Xanthomonas spp. indicated that the lineages identified here emerged in part through recent recombination events originating from xanthomonads associated with diverse hosts of isolation. Our results also suggest that the evolution of pathogenicity to pepper has likely emerged independently within X. perforans and in one lineage, was associated with the recombination-mediated remodeling of the Xps type II secretion and TonB transduction systems.\n\nImportanceThe emergence of novel pathogen lineages has important implications in the sustainability of genetic resistance as a disease management tool in agricultural ecosystems. In this study, we identified two novel lineages of X. perforans in Alabama. While one lineage was isolated from symptomatic pepper plants, confirming the host range expansion of X. perforans, the other lineage was isolated from tomato and acquired a novel transcription activation-like effector, pthXp1. Unlike AvrBs4, PthXp1overcomes Bs4-mediated resistance in tomato, indicating the evolution of this novel lineage towards fitness on this host. Our findings also show that different phylogenetic groups of the pathogen have experienced independent recombination events originating from multiple Xanthomonas species. This suggests a continuous gene flux between related xanthomonads associated with diverse plant hosts which results in the emergence of novel pathogen lineages and associated phenotypes, including host range expansion.

genomics↗