Mutant/mutation
The mutant expresses a C-terminal HA-tagged version of PbS23/SSP3 and expresses GFP under control of the constitutive hsp70 promoter

Protein (function)
PbS23/SSP3 was identified in SSH screen between salivary gland sporozoites versus merozoites and encode secretory protein having a predicted molecular mass of 50,4 kDa and a putative signal peptide (N-terminus) and transmembrane domain (C-terminus).

Phenotype
The staining of PbS23/SSP3-3XHA with an anti-HA antibody followed by revealing its immunoreactivity with anti-rabbit secondary antibody conjugated Alexaflour 594 confirmed expression in salivary gland sporozoites.

Analyses of a mutant lacking expression of PbS23/SSP3 (RMgm-4647) showed the following: Production of salivary gland sporozoites comparable to wild type. Normal sporozoite gliding motility, cell traversal and hepatocyte infection in vitro. Normal growth (size) of liver stages in vitro at 12, 36 and 62 hour after infection of hepatocytes. Evidence is presented for a significant reduction in the formation of hepatic merozoites in PbS23/SSP3 KO mutants as revealed by DAPI staining. (Strongly) reduced infectivity in vivo (no blood infections or prolonged period after intravenous injection of sporozoites or after mosquito bite).

See also a P. yoelii mutant RMgm-1107 lacking expression of SSP3: this mutant shows a defect in sporozoite motility whereas no defect was detected in sporozoite infectivity

Additional information
Quantitative real-time PCR analysis revealed maximal expression of PbS23/SSP3 in salivary gland sporozoite stage followed by midgut oocyst stages. The expression of PbS23/SSP3 was minimal during different time points of liver stage development and in mixed blood stages.

Other mutants