Single‐cell transcriptomic landscape of peripheral blood cells provides insights into adaptation of red‐eared sliders (Trachemys scripta elegans)

Abstract Red‐eared sliders ( Trachemys scripta elegans ), as one of the 100 most threatening aliens, have stronger immunity than the native species in response to environmental stress. Blood cells are an important component of immunity in the body. However, the blood cell researches of turtle are still in the traditional blood cell classification and morphological structure observation. Furthermore, turtle granulocytes cannot be accurately identified using traditional methods. Single‐cell RNA sequencing techniques have been successfully implemented to study cells based on the mRNA expression patterns of each cell. The present study profiled the transcriptomes of peripheral blood cells in red‐eared sliders to construct a single‐cell transcriptional landscape of the different cell types and explored environmental adaptation mechanism from the perspective of hematology. All 14 transcriptionally distinct clusters (platelets, erythrocytes1, erythrocytes2, CSF1R monocytes, POF1B monocytes, neutrophils, GATA2high basophils, GATA2low basophils, CD4 T cells, CD7 T cells, B cells, ACKR4 cells, serotriflin cells, and ficolin cells) were identified in the peripheral blood cells of the red‐eared sliders. In particular, a subtype of erythrocytes (erythrocytes1) that expressed immune signals was identified. Peripheral blood cells were grouped into three lineages: platelet, erythroid/lymphoid, and myeloid cell lineages. Furthermore, based on differentiation trajectory and up‐regulated gene expression, ACKR4 cells were newly identified as lymphocytes, and serotriflin and ficolin cells as granulocytes. The single‐cell transcriptional atlas of the peripheral blood cells in red‐eared sliders provided in the present study will offer a comprehensive transcriptome reference for the exploration of physiological and pathological hematology in this species.