Mutant/mutation
The mutant lacks expression of glutathione reductase (GR).

Protein (function)
Plasmodium species have a fully functional glutathione (GSH) redox system. GSH is synthesized by the sequential action of gamma-glutamylcysteine synthase (γ-GCS) and GSH synthase; both of the genes encoding these enzymes are present in the Plasmodium. In addition, GSH is  generated by recycling GSSG back to GSH via glutathione reductase (GR). De novo synthesis of GSH is not essential for survival of  P. berghei blood stages. Blood stages of parasites lacking the enzyme γ-GCS (Δγ-gcs; RMgm-204) showed only a minor reduction in growth rate compared to wild type parasites.  In contrast, Δγ-gcs parasites show a complete block in oocyst development and were unable to produce infectious sporozoites. These results indicate that de novo synthesis of GSH is pivotal for development in the mosquito.

Phenotype
The phenotype analyses indicate that GR is not essential for blood stage development. In contrast, a dramatic effect of the lack of GR expression was observed on development of the parasites in the mosquito. Infection of mosquitoes resulted in (reduced numbers of) small oocysts that did not produce sporozoites.

Through disruption of the gene encoding γ-GCS it has been shown that de novo GSH synthesis is not critical for P. berghei blood stage multiplication but is essential for oocyst development. The phenotype analyses of mutant parasites lacking expression of GR confirms that GSH metabolism is critical for the mosquito oocyst stage.

See also the P. berghei mutants RMgm-403 and RMgm-404 which also lack the expression of GR and which show a similar phenotype as the mutant described here.

Additional information

Other mutants
RMgm-403: An independent mutant lacking expression of GR
RMgm-404: An independent mutant lacking expression of GR
RMgm-204: A mutant lacking expression of gamma-glutamylcysteine synthetase (γ-GCS).