Biology subjects

Kopacek, P.

Publications and source records attributed to Kopacek, P..

4 recordsLinked to original sources

bioRxiv2026

Host-derived lipids license proliferation of sterol-auxotrophic tick cells and promote flavivirus output

Sterol molecules play indispensable roles in the biology of cells and organisms. Yet, arthropods, including ticks, lack the capacity for de novo sterol biosynthesis and must rely on exogenous sources. How these organisms sense and utilise exogenous lipids at the cellular level remains poorly understood. Here, we show that host cholesterol and linoleic acid act as essential external signals that license proliferation of Ixodes ricinus tick cells. In lipid-depleted conditions, cells fail to proliferate despite retaining intracellular cholesterol, indicating that exogenous lipids function as regulatory cues rather than merely structural components. We further demonstrate that tick cells exhibit a non-canonical intracellular distribution of cholesterol, with predominant accumulation in lysosome-associated compartments, and that lipid availability induces a coordinated transcriptional program involving lipid uptake and trafficking machinery. Importantly, we find that limiting host lipid availability significantly reduces extracellular RNA output of tick-borne encephalitis virus (TBEV) from infected tick cells, indicating that viral production is affected by the metabolic state of the host cell. Together, our findings establish host-derived lipids as key regulators of cellular state in a sterol-auxotrophic organism and identify lipid availability as a determinant of flavivirus output. This work provides a conceptual framework linking nutrient sensing, cell proliferation, and vector-pathogen interactions.

microbiology↗

bioRxiv2024

Whole genome sequencing of four Ixodes species expands understanding of tick evolution

Ticks, hematophagous acari, pose a significant threat by transmitting various pathogens to their vertebrate hosts during feeding. Despite advances in tick genomics, high-quality genomes were lacking until recently, particularly in the genus Ixodes, which includes the main vectors of Lyme disease. Here, we present the complete genome sequences of four tick species, derived from a single female individual, with a particular focus on the European species Ixodes ricinus, achieving a chromosome-level assembly. Additionally, draft assemblies were generated for the three other Ixodes species, I. persulcatus, I. pacificus and I. hexagonus. The quality of the four genomes and extensive annotation of several important gene families have allowed us to study the evolution of gene repertoires at the level of the genus Ixodes and of the tick group. We have determined gene families that have undergone major amplifications during the evolution of ticks, while an expression atlas obtained for I. ricinus reveals striking patterns of specialization both between and within gene families. Notably, several gene family amplifications are associated with a proliferation of single-exon genes. The integration of our data with existing genomes establishes a solid framework for the study of gene evolution, improving our understanding of tick biology. In addition, our work lays the foundations for applied research and innovative control targeting these organisms.

genomics↗

bioRxiv2022

Integrative assessment of the transcriptome and virome of the poultry red mite Dermanyssus gallinae.

Dermanyssus gallinae is a blood-feeding mite that parasitises on wild birds and farmed poultry. The D. gallinae mite has a short life cycle of fewer than two weeks from the egg to an egg-laying female. The remarkably swift processing of blood, together with the capacity to blood-feed in most developmental stages, makes this mite a highly debilitating pest. We have constructed developmental stage-specific transcriptomes, through Illumina RNA-seq, to mine the repertoire of protein-encoding mRNA transcripts, products of which participate in key processes that ensure the success of blood digestion, rapid ontogeny, and immunity. As a result of high reproductive capacity, the prevalence of D. gallinae in egg-producing poultry farms globally causes significant economic losses. Acaricides that are used to limit the reproduction of D. gallinae mites target cys-loop ion channels, which are widely shared across the phylogeny of invertebrates. To catalogue a comprehensive list of potential invertebrate-specific ion channels, we have constructed and analysed an additional RNA-seq library of D. gallinae micro-dissected midguts, a tissue with direct exposure to host blood and potential anti-parasitics. We phylogenetically defined groups of cys-loop proteins and probed their sensitivity to selected acaricides. Ultimately, we have catalogued all assembled transcripts and their expression values in a hyper-linked excel sheet with available sequences of individual contigs. The transcriptomic data were complemented by mass-spectrometry (MS)-based metabolite identification and by viability assays using selected inhibitors applied either by microinjection or through artificial membrane feeding. Additionally, we have described the RNA-virome of D. gallinae and identified a novel virus dubbed Red Mite Quaranjavirus 1.

microbiology↗

bioRxiv2018

Tracking Borrelia afzelii from infected Ixodes ricinus nymphs to mice suggests a direct ‘gut-to-mouth’ route of Lyme disease transmission

Quantitative tracking of Borrelia afzelii has shown that its transmission cycle differs from the salivary route of B. burgdorferi transmission by Ixodes scapularis. Borrelia afzelii are abundant in the guts of unfed Ixodes ricinus nymphs and their numbers continuously decrease during feeding. In contrast, spirochetes are not present in the salivary glands. Borrelia afzelii transmission starts during the early stages of feeding, spirochetes could be detected in murine skin within 1 day of tick attachment. Tick saliva is not essential for B. afzelii infectivity, the main requirement for successful host colonization being a change in outer surface protein expression that occurs in the tick gut during feeding. Spirochetes in vertebrate mode are able to survive within the host even if the tick is not present. On the basis of our data we propose that a direct gut-to-mouth route of infection appears to be the main route of B. afzelii transmission.\n\nImportanceLyme borreliosis is the most common vector-borne disease in the USA and Europe. The disease is caused by the Borrelia spirochetes and is transmitted through Ixodes ticks. A better understanding of how Borrelia spirochetes are transmitted is crucial for development of efficient vaccines for preventing Lyme borreliosis. Here we present that the transmission of European B. afzelii spirochetes by I. ricinus ticks significantly differs from the model transmission cycle described for American B. burgdorferi/I. scapularis. We suggest that B. afzelii is not transmitted via salivary glands but most likely through the midgut to mouthpart route. We further demonstrate that tick saliva is not important for B. afzelii transmission and infectivity. Therefore, we support early studies by Willy Burgdorfer, who proposed that Borrelia transmission occurs by regurgitation of infected gut contents. Our findings collectively point to the Borrelia-tick midgut interface as the correct target in our endeavours to combat Lyme borreliosis.

microbiology↗