The “sialome switch” of Ixodes scapularis at the single-cell resolution

Authors

• SA Bryant
• W Becker
• JA Berzofsky
• PB Olkhanud

Abstract

Tick salivary glands (SGs) secrete a complex saliva, assisting the blood feeding. Transcriptomic studies revealed salivary transcription profile switches at intervals, characterizing the phenomenon of "sialome switch". Here, using a transcriptomic approach, we explored the sialome of Ixodes scapularis adult female ticks fed on rabbits for different periods. Ticks were sorted in seven groups based on their weight. Groups categorized here represent the unfed, slow-feeding, and the rapid-feeding phases of tick feeding. Transcriptomic analysis showed dynamic expression with remarkable signatures for each phase, confirming the “sialome switch”. As a SG is composed of different types of acini which differ both morphologically and functionally, we performed a transcriptome at the single-cell level as well and validated the “sialome switch”. Interestingly, the analysis of scRNA-seq data revealed a substantial upregulation of mitochondrial genes in the fed groups, which can be attributed to the cellular hypertrophy observed when feeding progresses. A total of ten cellular clusters was observed and its distribution was influenced by the feeding. Notably, one cluster consisting of undifferentiated cells was found to be enriched in the SGs of unfed ticks. As feeding progresses, this cluster diminished, giving rise to different cell populations that expressed classical salivary genes. This cluster was identified as the trajectory root and the origin of all other clusters. Nuclei counting and PH3 staining indicated absence of cellular proliferation, supporting the idea that these undifferentiated cells differentiate into specialized cells when feeding starts. These findings offer a potential explanation for the plasticity observed in SG expression.

Scientific Focus Area: Cell Biology

This page was last updated on Monday, September 25, 2023