Abstract
MicroRNAs act as mRNA post-transcriptional regulators, playing important roles in cell differentiation, transcriptional regulation, growth, and development. In this study, microRNA expression profiles of Hyalomma anatolicum anatolicum ticks at different developmental stages were detected by high-throughput sequencing and functionally assessed. In total, 2,585,169, 1,252,678, 1,558,217, and 1,155,283 unique reads were obtained from eggs, larvae, nymphs, and adults, respectively, with 42, 46, 45, and 41 conserved microRNAs in these stages, respectively. Using eggs as a control, 48, 43, and 39 microRNAs were upregulated, and 3, 10, and 9 were downregulated in larvae, nymphs, and adults, respectively. MicroRNA-1 (miR-1) was expressed in high abundance throughout Ha. anatolicum development, with an average of nearly one million transcripts, and it is highly conserved among tick species. Quantitative real-time PCR (qPCR) showed that miR-1 expression gradually increased with tick development, reaching the highest level at engorgement. Differential tissue expression was detected, with significantly higher levels in the salivary glands and epidermis than in the midgut. Inhibition assays showed no significant change in body weight or spawning time or amount between experimental and control groups, but there was a significant difference (p < 0.01) in engorgement time. With miR-1 inhibition, ticks displayed obvious deformities during later development. To more fully explain the microRNA mechanism of action, the miR-1 cluster was analyzed according to the target gene; members that jointly act on Hsp60 include miR-5, miR-994, miR-969, and miR-1011. Therefore, microRNAs are critical for normal tick development, and the primary structure of the mature sequence of miR-1 is highly conserved. Nonetheless, different developmental stages and tissues show different expression patterns, with a certain role in prolonging feeding. miR-1, together with other cluster members, regulates mRNA function and may be used as a molecular marker for species origin, evolution analysis, and internal reference gene selection.
Highlights
Hyalomma anatolicum anatolicum belongs to the taxa Parasitiformes, Ixodoidea, Ixodidae, and Hyalomma
The molecular mechanisms were investigated, and the biological function of miR-1 in tick development was explored. This is the first report on the function of miR-1 in ticks, and we present the characteristics of tick development upon abnormal expression of miR-1
To identify microRNAs involved in different stages of Ha. anatolicum development, four small RNA (sRNA) libraries pooled from eggs, larvae, nymphs, and adults were constructed and sequenced using an Illumina HiSeq2000 high-throughput sequencer
Summary
Hyalomma anatolicum anatolicum belongs to the taxa Parasitiformes, Ixodoidea, Ixodidae, and Hyalomma. Ticks are only reported in the semidesert areas of Xinjiang Uyghur Autonomous Region in China (Ghosh et al, 2017). Ticks are distributed worldwide, including the former Soviet Union, India, Nepal, Pakistan and Central Asia, North Africa, and in eastern European countries. Sheep, camels, horses, donkeys, and a few wild animals; serve as a transmission vector of the Crimean–Congo hemorrhagic fever (Xinjiang hemorrhagic fever); can be naturally infected with Coxiella burnetii (Q fever); and can spread brucellosis and piriformis disease (Luo et al, 2003; Guan et al, 2009). Ticks cause serious harm to the livestock industry and public health. The quest for vaccine candidates to control these arthropod vectors remains a pivotal and rational approach to controlling these diseases. The 4D8 tick protective antigen has shown promising results in controlling ixodid tick infestations (Ghosh et al, 2019)
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