Amblyomma americanum Third Party assembly. Amblyomma americanum

The immune response of ticks plays a crucial role in their ability to survive and transmit pathogens. Hemocytes, the primary immune cells in arthropods, are key mediators of the tick's immune defense and provide insights into their immune responses. However, tick hemocytes' cellular complexity and heterogeneity have posed challenges for comprehensive characterization. This study employed single-cell RNA sequencing (scRNA-seq) to profile tick hemocytes and elucidate their transcriptional diversity. In the absence of a public genomic database for A. americanum, we assembled over 10 billion reads from A. americanum available on the SRA database, and created a pseudo-genome fasta and gff files by "stiching" the transcripts with 50 N's. The resulting transcriptome had a value of 89.0% complete BUSCOs, allowing the analysis of the scRNA-seq results using the 10x Genomics Cell Ranger software. We identified distinct subpopulations of hemocytes and characterized their unique gene expression profiles. We observed significant variation in immune-related gene expression between hemocyte subpopulations during hematophagy and in response to Ehrlichia infection, suggesting specialized functional roles. Our analysis revealed potential marker genes associated with specific hemocyte functions. Our study provides the first comprehensive single-cell atlas of tick hemocytes, shedding light on these cells' molecular diversity and immune functions. The findings enhance our understanding of tick-host interactions and offer a step toward our understanding of arthropod immunobiology.