PbAP2-FG2 and AP2R-2 function together as a transcriptional repressor complex essential for Plasmodium female development

Gametocyte development is a critical step in the life cycle of Plasmodium. Despite that numbers of studies in the gametocyte development have been conducted, the molecular mechanisms regulating this process remains to be fully understood. This study investigates the functional roles of two female-specific transcriptional regulators, PbAP2-FG2 and AP2R-2, in P. berghei. Knockout of pbp2-fg2 or ap2r-2 impairs female gametocyte development, resulting in developmental arrest during ookinete development. ChIP-seq analyses of these two factors indicated their colocalization on the genome, suggesting they function as a complex. These analyses also revealed that their target genes contained a variety of genes, including both male and female-enriched genes. Moreover, differential expression analyses showed that these target genes were upregulated through the disruption of pbp2-fg2 or ap2r-2, indicating that these two factors function as a transcriptional repressor complex in female gametocytes. Further target analysis demonstrated a significant overlap between the target genes of PbAP2-FG2 and AP2-G, suggesting that repression of early gametocyte genes activated by AP2-G is one of the key roles for this female transcriptional repressor complex. Our results indicate that the PbAP2-FG2-AP2-R2 complex-mediated repression of the target genes supports the female differentiation from early gametocytes. Author SummaryGametocyte development in Plasmodium parasites, a causative agent of malaria, is an essential step for their transmission from vertebrate hosts to mosquitoes. Gametocytes are sexual precursor cells produced from a subpopulation of asexual blood-stage parasites. Upon uptake by mosquitoes through blood feeding, the male and female gametocytes become microgametes and macrogametes, respectively, and then they fertilize and develop into the mosquito midgut invasive stage, called ookinete. Therefore, it is crucial to understand the underlying mechanisms regulating this developmental process. This study revealed that the two female transcriptional regulators, PbAP2-FG2 and AP2R-2, function together as an essential transcriptional repressor complex in P. berghei, the target genes of which include male, female, and early gametocyte genes activated by AP2-G. Our findings suggest that PbAP2-FG2 and AP2R-2 play multiple roles in supporting the development of female gametocytes from early gametocytes.