Integrated transcriptomic and proteomic analyses ofP. falciparumgametocytes: molecular insight into sex-specific processes and translational repression

Abstract

Sexual differentiation of malaria parasites into gametocytes in the vertebrate host and subsequent gamete fertilization in mosquitoes is essential for the spreading of the disease. The molecular processes orchestrating these transitions are far from fully understood. Here, we report the first transcriptome analysis of male and female Plasmodium falciparum gametocytes coupled with a comprehensive proteome analysis. In male gametocytes there is an enrichment of proteins involved in the formation of flagellated gametes; proteins involved in DNA replication, chromatin organization and axoneme formation. On the other hand, female gametocytes are enriched in proteins required for zygote formation and functions after fertilization; protein-, lipid- and energy-metabolism. Integration of transcriptome and proteome data revealed 512 highly expressed maternal transcripts without corresponding protein expression indicating large scale translational repression in P. falciparum female gametocytes for the first time. Despite a high degree of conservation between Plasmodium species, 260 of these ‘repressed transcripts’ have not been previously described. Moreover, for some of these genes, protein expression is only reported in oocysts and sporozoites indicating that repressed transcripts can be partitioned into short- and long-term storage. Finally, these data sets provide an essential resource for identification of vaccine/drug targets and for further mechanistic studies.

Sex-Specific Biology of the Human Malaria Parasite Revealed from the Proteomes of Mature Male and Female Gametocytes

“…In contrast, a number of MG-enriched proteins function in motility and DNA replication. Such sex-biased proteomes were further corroborated by the recent analysis of sorted P. falciparum MG and FG proteomes (52). Furthermore, we confirmed several of these new predictions of sex partitioning by tagging the endogenous genes with GFP.…”

“…These include PfABCG2, two acyl-CoA synthetases, proteins associated with de novo fatty acid synthesis, and enzymes associated with signaling lipid metabolism, which is in agreement with the finding that in P. falciparum there is a high demand for lipids at the gametocyte stage (43,44) and a need of de novo fatty acid synthesis for subsequent development in the free-living environment in a mosquito (42). Comparison with the recent P. falciparum sex-specific/biased proteomes largely confirmed these species-specific differences (supplemental Table S8D) (52).…”

“…Similarly, such type of proteins were also identified in almost all earlier gametocyte proteome work (14,15,18), including the recent P. falciparum sex-specific proteome identified by Lasonder et al (52). Whereas these proteins might be resulted from contaminating asexual stages, it should be rare or impossible in the present and recent studies (52) because both studies used sorted MG and FG that were cultured for an extended period and were supposedly devoid of asexual stages.…”

“…S4D, supplemental Table S9A and S9B). Sex-specific/biased Proteins in Plasmodium -Lasonder et al-recently separated mature MG and FG based on marker expression under the male-specific protein dynein heavy chain (PF3D7_1023100) and the female-specific protein Pfs47 and identified 1960 proteins (at least two unique peptides per protein) (52). This combined FG and MG proteome data set showed a strong correlation (r ϭ 0.77) with our combined proteome.…”

“…An attempt to identify sex-partitioned proteomes of the P. falciparum gametocytes relied heavily on species-species conservation and bioinformatic predictions (51), and thus might have missed important information underlying the true biological differences between these species. Most recently, a comprehensive proteome analysis of separated P. falciparum MG and FG coupled with transcriptome analysis was reported (52). This study identified divergent MG and FG proteomes similar to the sex-specific proteomes in the gametocytes of P. berghei.…”