Mutant/mutation
The mutant c57::gfp expresses a C-terminal GFP-tagged version of PIMMS57

Protein (function)
PfPIMMS57 encodes a 810 amino acid-long (94 kDa) protein with a predicted signal peptide (aa 1–26) that overlaps with a putative transmembrane domain albeit with low probability according to Phobius (0.343). A second transmembrane domain close to the carboxy terminus of PfPIMMS57 (aa 677–697) is predicted with very high probability (0.874). The P. berghei orthologue, PbPIMMS57, encodes a protein of 774 amino acid-long (90 kDa) protein with two putative transmembrane domains (aa 6–23 and aa 633–653) predicted with high probability (0.984 and 0.967, respectively). These data suggest that both proteins are putatively membrane-bound. Higher sequence conservation between PIMMS57 orthologues is observed in the second half of the proteins compared to the first half, pointing to a conserved functional role served by this region. A previous in silico analysis identified in PfPIMMS57, two P. falciparum serine/threonine protein phosphatase type I catalytic (PfPP1c) binding motifs, the RVxF motif, RRKVNF (aa 347–352) and the Fxx[RK] x[RK] motif, FNKILKR (aa 488–494). These motifs are not conserved in the other PIMMS57 orthologues   

Phenotype
Severely reduced sporozoite numbers, suggesting that insertion of GFP compromises the function of the  protein. Also HA-tagging resulted in reduced oocyst and sporozoite numbers.
See RMgm-4998 for a mutant lacking expression of PIMMS57, showing reduced oocyst and sporozoite formation

Additional information
Three genes were selected for analysis that exhibit highly abundant transcripts 24 h post blood feeding in the midguts of Anopheles coluzzii mosquitoes.
 
PIMMS01: PF3D7_0112100; PBANKA_0201700 
PIMMS57: PF3D7_1244500; PBANKA_1457700
PIMMS22: PF3D7_0814600; PBANKA_1422900 
((PIMMS: Plasmodium Infection of the Mosquito Midgut Screen)

PbPIMMS01 and PbPIMMS57 transcripts were highly abundant in purified mature ookinetes and not detectable in mixed blood stages and purified gametocytes. While PbPIMMS57 appears to be specific for ookinetes, low levels of PbPIMMS01 transcripts are also detected in mature oocysts and midgut sporozoites at 10 days and 15 days post blood-feeding. Like PfPIMMS22, expression of PbPIMMS22 starts in gametocytes and continues at high levels at 24 hour and peaks in midgut sporozoites at day 15.

Using the non-functional c57::gfp parasite line and the α-GFP antibody in western blot analysis, high levels of the PbPIMMS57::GFP fusion protein were detected in mature ookinetes, at the expected molecular weight of 117 kDa. This band was not detected in MBS or gametocytes or in the ANKA 2.34 background parasite line. Similarly, western blot analysis using the c57::3xha transgenic line and the α-HA antibody confirmed  expression of the PbPIMMS57::3xHA protein in the ookinete at the expected molecular weight and its absence from gametocytes. The protein was mostly detected in the Triton insoluble fraction, indicating membrane association. No band was detected in the c507 reference line. To validate the ookinete expression of PbPIMMS57, the αPbc57 peptide antibody was utilized. In westerns, the α-Pbc57 antibody detected in ookinetes a band at about 90 kDa, close to the predicted molecular weight of PbPIMMS57. This band was not seen in blood stages, gametocytes. Fractionation assays revealed that, in ookinetes, PbPIMMS57 is mostly found in the Triton X-100 insoluble fraction with low amounts also seen in the Triton X-100 soluble fraction, suggesting that Pbc57 is membrane associated. These results agree with the prediction of transmembrane domains in this protein. The α-Pbc57 peptide antibody did not work in IFAs. IFAs on the developmentally compromised c57::gfp and c57::3xha transgenic lines revealed cytoplasmic localization of the PbPIMMS57::GFP and PbPIMMS57::3xHA fusion proteins with bias for the ookinete convex side, especially for the former, pointing to a possible involvement of the protein with ookinete motility or invasion machinery. However, given that both types of fusions lead to developmentally compromised parasites, these data must be interpreted with caution.

From the abstract:
PIMMS01 and PIMMS57 are specifically and highly expressed in ookinetes, while PIMMS22 transcription starts already in gametocytes and peaks in sporozoites. All three genes show strong phenotypes associated with the ookinete to oocyst transition, as their disruption leads to very low numbers of oocysts and complete abolishment of transmission. PIMMS22 has a secondary essential function in the oocyst. 

Other mutants