Transcriptional heterogeneity and tightly regulated changes in gene expression during Plasmodium berghei sporozoite development

Despite the critical role of Plasmodium sporozoites in malaria transmission, we still know little about the mechanisms underlying their development in mosquitoes. Here, we use single-cell RNA sequencing to characterize the gene expression profiles of 16,038 Plasmodium berghei sporozoites isolated throughout their development from midgut oocysts to salivary glands, and from forced salivation experiments. Our results reveal a succession of tightly regulated changes in gene expression occurring during the maturation of sporozoites and highlight candidate genes that could play important roles in oocyst egress, sporozoite motility, and the mechanisms underlying the invasion of mosquito salivary glands and mammalian hepatocytes. In addition, the single-cell data reveal extensive transcriptional heterogeneity among parasites isolated from the same anatomical site, suggesting that Plas-modium development in mosquitoes is asynchronous and regulated by intrinsic as well as environmental factors. Finally, our analyses show a decrease in transcriptional activity preceding the translational repression observed in mature sporozoites and associated with their quiescent state in salivary glands, followed by a rapid reactivation of the transcriptional machinery immediately upon salivation.

Automated summary

This study used single-cell RNA sequencing to characterize the gene expression profiles of Plasmodium berghei sporozoites throughout their development in mosquitoes. The results revealed tightly regulated changes in gene expression and highlighted candidate genes involved in various functions. Additionally, the study showed transcriptional heterogeneity among parasites and suggested that Plasmodium development in mosquitoes is asynchronous and regulated by intrinsic and environmental factors. Finally, the analysis demonstrated a decrease in transcriptional activity followed by rapid reactivation upon salivation in mature sporozoites.