Single cell RNA-seq analysis of oral tissues from independent dataset. a Seven-cell types were identified by the cell markers; cells were clustered by UMAP method. b Heatmap of cell markers for identifying cell types. c Scatter plots of all the cells with ACE2 expression. d Violin plot of ACE2 expression across different oral sites. e Violin plot of ACE2 expression across different cell types. f Scatter plots of tongue epithelial cells with ACE2 expression