Mutant/mutation
The mutant lacks expression of SPM3

Protein (function)
Mature gametocytes of Plasmodium (P.) falciparum display a banana (falciform) shape conferred by a complex array of subpellicular microtubules (SPMT) associated to the inner membrane complex (IMC). Microtubule associated proteins (MAPs) define MT populations and modulate interaction to pellicular components. Several MAPs have been identified in Toxoplasma gondii and homologues can be found in the genome of Plasmodium species, but the function of these proteins for asexual and sexual development of malaria parasites is still unknown. Here we identified a novel subpellicular MAP, termed SPM3, that is conserved within the genus Plasmodium. 
The number of SPMTs varies across life cycle stages. For instance, merozoites of P. falciparum possess 2–4 SPMTs, whereas ookinetes have 60, sporozoites 14 and gametocytes 21 SPMTs

Phenotype
Normal sporozoite formation inside oocysts. Strongly reduced sporozoite numbers in salivary glands. Strongly reduced (aberrant) motility.
Evidence is presented that:
- SPM3 deletion disturbs subpellicular microtubule (SPMT) architecture in sporozoites

Additional information
Conditional knockdown and targeted gene disruption of Pfspm3 in P. falciparum cause severe morphological defects during gametocytogenesis leading to round, non-falciform gametocytes with an aberrant subpellicular microtubules (SPMT) pattern. In contrast, Pbspm3 knockout in P. berghei, a species with round gametocytes, caused no defect in gametocytogenesis, but sporozoites displayed an aberrant motility and a dramatic defect in sporozoite invasion of salivary glands leading to a decreased efficiency in transmission. Electron microscopy revealed a dissociation of the SPMT from the inner membrane complex (IMC) in Pbspm3 knockout parasites suggesting a function of SPM3 in anchoring microtubules (MTs) to the inner membrane complex (IMC).

Analysis of a mutant expressing a C-terminal GFP-tagged version of SPM3 (RMgm-5265) showed expression in oocysts and sporozoites. In sporozoites, the fluorescent signal extended from the apical end towards the rear around the nucleus. Subsequent co-staining with an anti-tubulin antibody revealed co-localization of PbSPM3-GFP with tubulin (Figure 4A) in midgut and salivary gland sporozoites. C-terminal tagging of PbSPM3 with GFP did not affect parasite life cycle progression, as SPM3-GFP parasites showed normal midgut infection and midgut oocyst numbers as well as numbers of both midgut and salivary gland sporozoites comparable to wild-type.

For P. falciparum SPM3 evidence is presented that:
- PfSPM3 is a Plasmodium-specific microtubule-associated protein in P. falciparum merozoites
- PfSPM3 is dispensable for intraerythrocytic development
- PfSPM3 is important for falciform gametocyte morphology

Other mutants