Lab

Molecular Biology of Ticks

About the lab

Our lab is focused on molecular descriptions of proteins that are key for the successful blood-feeding of ticks (mainly Ixodes ricinus) and the poultry red mite (Dermanyssus gallinae), or play a role in the acquisition&transmission of tick-borne pathogens. We cover a wide range of topics incl. metal biology, description of proteolytic apparatus, systemic and epithelial immunity to experimental infection, functional microbiota integration, and mapping of protein-ligand interactions. Our keystone experimental approaches comprise:
i) ex vivo artificial membrane feeding of all developmental stages of Ixodes ricinus ticks and adults of D. gallinae mites
ii) RNA interference in Ixodes spp. ticks or D. gallinae mites
iii) Acquisition & transmission model for Borrelia sp. and Babesia sp.

Featured research (6)

In addition to being vectors of pathogenic bacteria, ticks also harbor intracellular bacteria that associate with ticks over generations, aka symbionts. The biological significance of such bacterial symbiosis has been described in several tick species but its function in Ixodes ricinus is not understood. We have previously shown that I. ricinus ticks are primarily inhabited by a single species of symbiont, Midichloria mitochondrii, an intracellular bacterium that resides and reproduces mainly in the mitochondria of ovaries of fully engorged I. ricinus females. To study the functional integration of M. mitochondrii into the biology of I. ricinus, an M. mitochondrii-depleted model of I. ricinus ticks was sought. Various techniques have been described in the literature to achieve dysbiosed or apo-symbiotic ticks with various degrees of success. To address the lack of a standardized experimental procedure for the production of apo-symbiotic ticks, we present here an approach utilizing the ex vivo membrane blood feeding system. In order to deplete M. mitochondrii from ovaries, we supplemented dietary blood with tetracycline. We noted, however, that the use of tetracycline caused immediate toxicity in ticks, caused by impairment of mitochondrial proteosynthesis. To overcome the tetracycline-mediated off-target effect, we established a protocol that leads to the production of an apo-symbiotic strain of I. ricinus, which can be sustained in subsequent generations. In two generations following tetracycline administration and tetracycline-mediated symbiont reduction, M. mitochondrii was gradually eliminated from the lineage. Larvae hatched from eggs laid by such M. mitochondrii-free females repeatedly performed poorly during blood-feeding, while the nymphs and adults performed similarly to controls. These data indicate that M. mitochondrii represents an integral component of tick ovarian tissue, and when absent, results in the formation of substandard larvae with reduced capacity to blood-feed. CITATION Guizzo MG, Hatalová T, Frantová H, Zurek L, Kopá č ek P and Perner J (2023) Ixodes ricinus ticks have a functional association with Midichloria mitochondrii.
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.
It has been demonstrated that impairing protein synthesis using drugs targeted against tRNA amino acid synthetases presents a promising strategy for the treatment of a wide variety of parasitic diseases, including malaria and toxoplasmosis. This is the first study evaluating tRNA synthetases as potential drug targets in ticks. RNAi knock-down of all tested tRNA synthetases had a strong deleterious phenotype on Ixodes ricinus feeding. Our data indicate that tRNA synthetases represent attractive, anti-tick targets warranting the design of selective inhibitors. Further, we tested whether these severely impaired ticks were capable of transmitting Borrelia afzelii spirochaetes. Interestingly, biologically handicapped I. ricinus nymphs transmitted B. afzelii in a manner quantitatively sufficient to develop a systemic infection in mice. These data suggest that initial blood-feeding, despite the incapability of ticks to fully feed and salivate, is sufficient for activating B. afzelii from a dormant to an infectious mode, enabling transmission and dissemination in host tissues.
An anti-tick mRNA cocktail vaccine promotes tick detachment and prevents transmission of tick-borne infection in guinea pigs (Sajid et al.).
Ticks, notorious blood-feeders and disease-vectors, have lost a part of their genetic complement encoding haem biosynthetic enzymes and are, therefore, dependent on the acquisition and distribution of host haem. Solute carrier protein SLC48A1, aka haem-responsive gene 1 protein (HRG1), has been implicated in haem transport, regulating the availability of intracellular haem. HRG1 transporter has been identified in both free-living and parasitic organisms ranging from unicellular kinetoplastids, nematodes, up to vertebrates. However, an HRG1 homologue in the arthropod lineage has not yet been identified. We have identified a single HRG1 homologue in the midgut transcriptome of the tick Ixodes ricinus, denoted as Ir HRG, and have elucidated its role as a haem transporter. Data from haem biosynthesis-deficient yeast growth assays, systemic RNA interference and the evaluation of gallium protoporphyrin IX-mediated toxicity through tick membrane feeding clearly show that Ir HRG is the bona fide tetrapyrrole transporter. We argue that during evolution, ticks profited from retaining a functional hrg1 gene in the genome because its protein product facilitates host haem escort from intracellularly digested haemoglobin, rendering haem bioavailable for a haem-dependent network of enzymes.

Lab head

Jan Perner
Department
  • Institute of Parasitology

Members (10)

Petr Kopacek
  • The Czech Academy of Sciences
Radek Síma
  • The Czech Academy of Sciences
Ondrej Hajdusek
  • Institute of Parasitology Biology Centre, ASCR
Daniel Sojka
  • Biology Centre CAS
Veronika Urbanová
  • Institute of Parasitology Biology Centre, ASCR
David Hartmann
  • Institute of Parasitology Biology Centre, ASCR
Helena Frantová
  • Institute of Parasitology Biology Centre, ASCR
Tereza Hatalová
  • Institute of Parasitology Biology Centre, ASCR
Petr Kopáček
Petr Kopáček
  • Not confirmed yet
Iva Hánová
Iva Hánová
  • Not confirmed yet