Mutant/mutation
The mutant lacks expression of aquaglyceroporin (AQP).

Protein (function)
Aquaporins constitute a family of cellular water and solute channels. They are functionally divided into two groups, the aquaporins, which are water-specific channels, and aquaglyceroporins, which are highly permeated by glycerol and other solutes and variably permeated by water. Aquaglyceroporins are the only glycerol channels identified in mammals. A single aquaglyceroporin is present in the genome of  P. falciparum (PfAQP). PfAQP has significant homology with the Escherichia coli glycerol facilitator GlpF, and is expressed during various intraerythocytic stages of the parasite where it is localized to the parasite plasma membrane.

Phenotype
Phenotype analyses have been reported in the two references mentioned above
The phenotype analyses indicate that AQP is not essential for blood stage development. Blood stages were viable and morphologically indistinguishable from WT parasites in Giemsa-stained blood smears. Mutant parasites had a slightly reduced growth rate in 4-week-old naïve female Swiss–Webster mice and mice infected with mutant parasites exhibited a more prolonged survival as compared with wild type parasites.

Compared to wild-type parasites, PbAQP-null sporozoites exhibit a delay in blood stage infection due to slower replication in hepatocytes, resulting in retardation of merosome production. Furthermore, PbAQP disruption results in a significant reduction in erythrocyte infectivity by hepatocyte-derived merozoites

Additional information
Expression of AQP was analysed by Western and IFA using a rabbit polyclonal antibody against a synthetic peptide corresponding to the last 17 amino acids of the C terminus of AQP. AQP was expressed in all blood stages with a clear increase in expression in trophozoite and schizont stages. AQP was localized at the parasite plasma membrane in all of the intraerythrocytic forms. There was no PbAQP staining observed at the erythrocyte plasma membrane or in the erythrocyte cytosol.

The uptake of the radiolabeled glycerol into the erythrocytes infected with mutant parasites was low compared with erythrocytes infected with wild type parasites and similar to that observed in uninfected erythrocytes.

RT-PCR analyses show: PbAQP is expressed in the sporozoite mosquito stage and is detected at low levels in intrahepatic parasites at the onset of hepatocyte infection. As the parasites progress to late hepatic stages, PbAQP transcription increases and PbAQP localizes to the plasma membrane of hepatic merozoites (as shown by IFA using anti-PbAQP antibodies).

Evidence is presented that: 'Hepatic merozoites incorporate exogenous glycerol into glycerophospholipids and PbAQP-null merozoites contain less phosphatidylcholine than wild-type merozoites, underlining the contribution of Plasmodium AQP to phospholipid syntheses'.

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