BioProject

Malarial parasite pathogenicity results from its ability to invade and remodel red blood cells (RBCs), expressing antigenic variant proteins for immune evasion and survival, and then to egress from the host cell. More...

Malarial parasite pathogenicity results from its ability to invade and remodel red blood cells (RBCs), expressing antigenic variant proteins for immune evasion and survival, and then to egress from the host cell. These sequential processes require concerted actions of a large number of proteins during the intraerythrocytic developmental cycle (IDC), but the molecular basis of the required regulation is only partially understood. Here, we have characterized an essential Apicomplexan AP2 (ApiAP2) transcription factor (we refer to it as PfAP2-P; Pathogenesis) that shows two peaks of expression during the IDC at 16- and 40-hour post invasion (h.p.i.). When expression of PfAP2-P at 40 h.p.i. was disrupted using an inducible gene knockout approach, ∆PfAP2-P parasites unable to form mature merozoites and egress from the host RBCs owing to strong down-regulation of several known egress- and invasion-associated genes, in addition to several novel hypothetical genes of thought to be involved in these key life cycle processes during the IDC. Disruption of PfAP2-P expression at 16 h.p.i. results in transcriptional activation of virtually majority of silenced var genes observed at both bulk and single cell level. This is also reflected by significantly higher level of recognition of the exported proteins on the ∆PfAP2-P parasite-infected RBCs by pooled sera from malaria-exposed individuals from endemic region. In addition, over-expression of many early gametocyte marker genes was also observed in ∆PfAP2-P parasites at both 40 h.p.i., and at 16 h.p.i. PfAP2-P directly regulates these genes by binding to their promoter region or indirectly through 14 other down-stream AP2 transcription factors. Taken together, we conclude that PfAP2-P is an upstream transcriptional regulator that participates in mutually exclusive expression pattern shown by the var family of genes and a critical determinant of parasite’s growth during the IDC. Overall design: Single-cell RNA-seq was conducted on parasites from two stages i.e. 16 h.p.i. and 40 h.p.i. Conditional knockout of PfAP2-P was carried out by adding 10nM of Rapamycin to the culture and as a control same volume of DMSO was added to the culture. For 40 h.p.i. parasites, DMSO (control) or Rapamycin (to induce PfAP2-P knockout) was added to culture at 16 h.p.i. in the same cycle of sample collection. For 16 h.p.i. parasites, DMSO (control) or Rapamycin (to induce PfAP2-MRP knockout) was added to cultures at 35 h.p.i. in cycle 0 and parasites were collected at 16 h.p.i. in cycle 1. Less...