Mutant/mutation
In the 'promoter swap mutant': the promoter of icm1 has been replaced with the asexual blood stage promoter clag9 (PBANKA_140060). This promoter is active in asexual blood stages but not in gametocytes.

Protein (function)
See additional information below.

Phenotype
RT-PCR analysis confirmed a two-fold reduction in pbicm1 expression in purified P^clagCM1 gametocytes. Although P^clagICM1 gametocytes were microscopically indistinguishable from their wild-type (WT) counterparts, they did not form active exflagellation centers upon activation. PbICM1 down-regulation led to significant decreases in axoneme formation, egress from the host RBC, and DNA replication, indicating an early requirement for PbICM1 in male gametogenesis.
A strongly attenuated calcium mobilization was consistently observed in P^clagICM1

Additional information
From the paper:
'We identify a multipass membrane protein, termed important for calcium mobilization-1 (ICM1; Pf3D7_1231400) that interacts with and is phosphorylated by PKG in two different Plasmodium developmental stages and species. Through stage-specific knockdown and reverse genetic approaches, we show that ICM1 is essential for calcium mobilization in both the clinically relevant asexual blood stages and in gametocytes that mediate transmission to mosquitoes. Our findings highlight this putative transporter or channel as a crucial link between PKG function and calcium signaling'.
PKG is involved in release of merozoites from red blood cells and hepatocytes, induction of gametogenesis and parasite transmission upon ingestion of gametocytes by a blood-feeding mosquito, and sustaining cellular motility necessary for parasite dissemination. A major function of PKG in all these processes is the tightly regulated mobilization of calcium from intracellular stores within seconds of activation

In the paper evidence is presented that:
- ICM1 may represent a structurally divergent polytopic membrane protein with architectural similarities to mammalian channels, transporters, and IP3 receptors. 
- ICM1 is phosphorylated in a PKG-dependent manner 
- Stage-specific knockdown of PbICM1 reveals a crucial role in early calcium mobilization required to initiate gametogenesis

Analysis of a mutant expressing HA-tagged ICM1 (RMgm-4993) showed the following:
No signal was observed for PbICM1-HA3 in Western blot analysis of schizont or gametocyte extracts from this line, possibly due to low abundance of PbICM1. Consistent with this observation, no specific immunofluorescence signal could be observed in both schizonts and gametocytes. Nevertheless, immunoprecipitation (IP) of PbICM1-HA3 from extracts of both schizonts and gametocytes recovered multiple peptides, identified by MS to encompass up to 28% coverage of PbICM1. As expected, based on the PbPKG IPs, PbPKG was the most enriched protein coimmunoprecipitated with PbICM1-HA3 in both stages. Notably, no peptides from PbCDPK1 or PbCDPK4 were recovered from either immuno-precipitate, confirming that these kinases do not interact with PbPKG or PbICM1 as previously suggested.

Other mutants