Proteomic analysis of zygote and ookinete stages of the avian malaria parasite Plasmodium gallinaceum delineates the homologous proteomes of the lethal human malaria parasite Plasmodium falciparum

Abstract

Delineation of the complement of proteins comprising the zygote and ookinete, the early developmental stages of Plasmodium within the mosquito midgut, is fundamental to understand initial molecular parasite-vector interactions. The published proteome of Plasmodium falciparum does not include analysis of the zygote/ookinete stages, nor does that of P. berghei include the zygote stage or secreted proteins. P. gallinaceum zygote, ookinete, and ookinete-secreted/released protein samples were prepared and subjected to Multidimensional protein identification technology (MudPIT). Peptides of P. gallinaceum zygote, ookinete, and ookinete-secreted proteins were identified by MS/MS, mapped to ORFs (> 50 amino acids) in the extent P. gallinaceum whole genome sequence, and then matched to homologous ORFs in P. falciparum. A total of 966 P. falciparum ORFs encoding orthologous proteins were identified; just over 40% of these predicted proteins were found to be hypothetical. A majority of putative proteins with predicted secretory signal peptides or transmembrane domains were hypothetical proteins. This analysis provides a more comprehensive view of the hitherto unknown proteome of the early mosquito midgut stages of P. falciparum. The results underpin more robust study of Plasmodium-mosquito midgut interactions, fundamental to the development of novel strategies of blocking malaria transmission.

Figure 1

The bar diagram shows the percentage of P. falciparum orthologous proteins with secretory/cell surface associated domains among the different functional class of proteins. The P. falciparum orthologs were identified in the zygote, ookinete, and ookinete secretomes of P. gallinaceum.

Figure 2

Venn Diagram showing the unique and shared orthologs of P. falciparum found in zygotes (Z), ookinetes (O), and ookinete-secreted proteins (S) of P. gallinaceum by MudPIT analysis.

Figure 3

Pie chart showing distribution of different functional classes of P. falciparum ortholog proteins in zygote, ookinete, and ookinete-secreted proteins of P. gallinaceum. (A, zygote; B, ookinete; C, secretome).