The Dynamic Changes Of Gene Expression Patterns And Microflora Of Ixodes Persulcatus During The Blood Feeding Process

The tick Ixodes persulcatus is the predominant tick species in Northeastern China, and it is a major vector in transmission of tick-borne diseases. As obligate hematophagous ectoparasites, the blood feeding is critical for ticks to complete their life cycle, and also has an impact on pathogen and microbiome colonization and transmission. Thus far, little is known about the dynamic physiological events and microbiome of I. persulcatus during the blood feeding process. Additionally, the pathogenic mechanisms for tick-borne diseases are as yet unclear.In this study, we performed experiments to resolve these concerned issues, and generate results as follows:(1) A reference transcriptome of I. persulcatus ticks, which was composed of56900unigenes, was obtained by Illuminia sequencing. Additionally, transcriptional data indicated that the I. persulcatus tick might serve as a potential vector of Leishmania protozoa.(2) The gene expression profiles of I. persulcatus at different feeding phases revealed that pronounced changes were induced by a blood meal. We found that12,332unigenes were significantly differentially expressed between unfed and semi-engorged ticks, and3,261unigenes were significantly differentially expressed between semi-engorged and fully engorged ticks. GO enrichment analysis showed that the pronounced changes in gene expression profiles were mainly involved in blood acquisition, nutrient metabolism, respiratory processes, hormone synthesis, egg development, immune responses, ROS detoxification, transcription and translation.(3) By comprehensive analyses of metabolic detoxification and antioxidant systems, we showed that these supergene families contain expanded and species-specific compositions and play crucial roles in responding to xenobiotic detoxification and oxidative stress during the blood-feeding period.(4) By V416S rRNA amplicon Illumina sequencing, we investigated the microbiome of I. persulcatus before and after the blood feeding, as well as the microbiome in rat blood after tick bites. Overall,373,289and441bacterial genera were assigned to unfed ticks, fed ticks and rat blood, respectively. Our data showed that237bacterial genera were suspected to be pathogens of vertebrates because they were commonly detected in all samples.(5) By using tick-borne Lyme spirochaetes (Borrelia burgdorferi B31A3) as an experimental model, we revealed its pathogenic mechanism for mammals. We constructed the BBA68-BBA73mutants via homologous recombination and estimated their infectivity by animal model. Our data showed that BBA68, BBA69and BBA71were essential for mammalian infection by needle inoculation.(6) The antisera against B. burgdorferi B31A3and B. garinii NMJW1were prepared, and then were used to detect the cultured spirochetes and the spirochetes in larvae tick midgut by immunofluorescence. Additionally, we investigated the response of rat antisera, which were collected one month after infested by filed-collected ticks, against two different genospecies spirochetes by immunoblot method and analyzed the frequency of protein bands with different Borrelia.All of the data presented here will deepen our understanding of the physiological responses of ticks, as well as the interactions between microbiome and vectors during the blood feeding process. In addition, it also facilitates the development of surveillance and management strategies for tick-borne diseases.