Single-cell RNA sequencing reveals developmental heterogeneity among P. berghei sporozoites Gene expression profiles of P. berghei midgut and salivary gland sporozoites at single-cell resolution

In the malaria-causing parasite's life cycle, Plasmodium sporozoites must travel from the midgut of a mosquito to the salivary glands before they can infect a mammalian host. Only a fraction of sporozoites complete the journey. Since salivary gland invasion is required for transmission of sporozoites, insights at the molecular level can contribute to strategies for malaria prevention. In this study, we use a droplet-based single-cell RNA sequencing workflow to analyze the transcriptomes of over 8000 Plasmodium berghei sporozoites derived from the midguts and salivary glands of Anopheles stephensi mosquitoes. Our analysis corroborates findings from previous transcriptomic studies as we identify many of the known markers associated with sporozoite infectivity and motility. Additionally, we identify new markers, providing new insights to gene usage in sporozoites residing in different anatomical sites of the mosquito. Together, our work resolves the developmental time-course of P.berghei sporozoites as it develops in the mosquito and provides a clearer picture of gene expression profiles of late-stage midgut sporozoites. In highlighting transcriptomic differences among sporozoites, we establish the utility of droplet-based single-cell technology for genome-wide transcriptomic profiling of Plasmodium sporozoites.