Background: The ixodid tick Dermacentor marginatus is a vector of many pathogens wide spread in Eurasia. Studies of gene sequence on many tick species have greatly increased the information on tick protective antigen which might have the potential to function as effective vaccine candidates or drug targets for eco-friendly acaricide development. In the current study, RNA-seq was applied to identify D. marginatus sequences and analyze differentially expressed unigenes. Methods: To obtain a broader picture of gene sequences and changes in expression level, RNA-seq was performed to obtain the whole-body transcriptome data of D. marginatus adult female ticks after engorgement and long-term starvation. Subsequently, the real-time quantitative PCR (RT-qPCR) was applied to validate the RNA-seq data. Results: RNA-seq produced 30,251 unigenes, of which 32% were annotated. Gene expression was compared among groups that differed by status as newly molted, starved and engorged female adult ticks. Nearly one third of the unigenes in each group were differentially expressed compared to the other two groups, and the most numerous were genes encoding proteins involved in catalytic and binding activities and apoptosis. Selected up-regulated differentially expressed genes in each group were associated to protein, lipids, carbohydrate and chitin metabolism. Blood-feeding and long-term starvation also caused genes differentially expressed in the defense response and antioxidant response. RT-qPCR results indicated 6 differentially expressed transcripts showed similar trends in expression changes with RNA-seq results confirming that the gene expression profiles in transcriptome data is in consistent with RT-qPCR validation. Conclusions: Obtaining the sequence information of D. marginatus and characterizing the expression pattern of the genes involved in blood-feeding and during starvation would be helpful in understanding molecular physiology of D. marginatus and provides data for anti-tick vaccine and drug development for controlling the tick. Graphical

Li C, et al. J Vet Sci. 2025 Feb;26:e19. https://doi.org/10.4142/jvs.24196

Background: Hyalomma asiaticum , which acts as a vector of zoonotic pathogens, relies on its innate immune system for defense. Methods: Unfed adult female H. asiaticum ticks were injected with Escherichia coli (Gram-negative) or Staphylococcus aureus (Gram-positive), with PBS-injected ticks as controls. After 24 h, RNA sequencing (RNA-Seq) was performed to compare transcriptomic profiles. Differential expression analysis, KEGG pathway enrichment, and phylogenetic characterization of defensin genes were conducted. RT-qPCR was used to validate selected defensin expression levels. Results: Transcriptome assembly yielded 195,132 unigenes. Principal component analysis (PCA) clearly separated the PBS control, E. coli -challenged (EC), and S. aureus -challenged (SA) groups. A total of 4,294 and 4,582 differentially expressed genes (DEGs) were identified in the EC and SA groups, respectively, compared to the PBS control. KEGG pathway enrichment analysis revealed that the MAPK signaling pathway and the Ras signaling pathway were commonly activated in both infection groups. In contrast, the lysosome pathway was significantly enriched among down-regulated DEGs in both EC and SA groups. Fifteen putative defensin genes were identified from the transcriptome, featuring conserved RVRR, CXXXC and CXC motifs. Several of these defensin isoforms were significantly up-regulated following bacterial challenge, indicating their involvement in the antibacterial response. Conclusion: This comparative transcriptomic study provides a comprehensive characterization of the defensin repertoire and immune signaling responses of H. asiaticum to Gram-negative and Gram-positive bacterial challenges. The shared activation of the MAPK pathway, together with significantly enrichment of Ras signaling pathways, reveals both common and distinct antibacterial defense strategies. The strong up-regulation of defensins and the down-regulation of lysosome highlight key transcriptional events. These findings offer a valuable resource for understanding tick innate immunity and may inform future interventions for tick-borne disease control.

Background: Hyalomma anatolicum is an important vector of veterinary and zoonotic pathogens, posing potential threats to livestock production and public health. Against the background of rising antibiotic resistance worldwide, it is necessary to explore new antimicrobial candidates. Tick defensins exhibit stable structures and strong antimicrobial activity, making them a valuable resource for the development of novel antibacterial substances. Methods: This study identified and characterized two defensin genes, Han-Def1 and Han-Def2 , from H. anatolicum that were upregulated upon bacterial challenge. The genes were cloned, recombinantly expressed, and assessed for antimicrobial, hemolytic, and antioxidant activities. Results: Bioinformatic analysis confirmed that Han-Def1 and Han-Def2 are cationic defensins with a conserved cysteine-stabilized α / β fold, clustering phylogenetically with other known ixodid defensins. Both recombinant proteins exhibited potent bactericidal activity against livestock-associated Staphylococcus aureus , Enterococcus faecalis , Bacillus subtilis , with Han-Def1 displaying superior efficacy. Notably, neither peptide inhibited the Gram-negative Pseudomonas aeruginosa and Escherichia coli . At a high concentration of 750 μg/mL (182 μM for rDef1 and 175 μM for rDef2), the hemolytic rate against sheep erythrocytes was <2%, indicating excellent biocompatibility. Both defensins also possessed in vitro antioxidant capacity. Conclusion: Collectively, Han-Def1 and Han-Def2 are low-toxicity, selective antimicrobial peptides with potential for developing therapeutics against drug-resistant Gram-positive infections in livestock.

Xinjiang, located in Northwest China, is characterized by diverse terrain and climates, which provides suitable habitats for many different tick species. To clarify the species composition, distribution, ecological adaptation and phylogenetic relationships of ticks in this region, questing ticks were collected. Morphological identification combined with COI gene sequence analysis was used for species identification and phylogenetic analysis. A total of 836 adult ticks were collected, belonging to three species: Dermacentor marginatus, Hyalomma asiaticum and Rhipicephalus turanicus. COI gene sequence confirmed identification accuracy. Phylogenetic analysis showed D. marginatus formed two clades as Central Asia-China Xinjiang and Europe-West Asia, R. turanicus from Xinjiang, Central Asia and the Middle East clustered into one monophyletic clade, and H. asiaticum formed a monophyletic clade without obvious geographical differentiation. The three species showed obvious niche differentiation related to habitat and host. The close phylogenetic affinity between Xinjiang and neighboring Central Asian tick populations highlights the need for cross-border tick research. This study may provide basic data for tick and tick-borne disease control in Xinjiang and a reference for tick-borne pathogen research.