Mutant/mutation
The mutant lacks expression of Chitinase (CHT1; Genbank accession number: AJ305256).

Protein (function)
CHT1, a secreted protein, is expressed in the ookinete stage and located in the micronemes. It contains putative proenzyme and chitin-binding domains. Chitinases are enzymes that hydrolize chitin, a (1-4)-β homopolymer of N-acetylglucosamine.

Phenotype
The phenotype analyses indicate a role during the transition of the ookinete into the oocyst stage (see also 'Additional information'). However, CHT1 is not essential for mosquito infectivity.

Additional information
Chitinase activity is thought to be critical for ookinetes to penetrate the chitin-containing peritophic matrix and midgut epithelial cells.
Feeding of in vitro cultured mature mutant ookinetes to A. stephensi resulted in the same reduction in oocyst formation as was found after feeding mutant gametocytes. In the ookinete feeds, the ookinetes invade the midgut cells before a perithrophic membrane is formed, suggesting that P. berghei chitinase is not involved in penetration of the perithrophic membrane.
The  chitinase inhibitor allosamidin effectively abolished oocyst development of P. falciparum and P. gallinaceum. This inhibitor did not affect P. berghei infectivity in A. stephensi as measured by oocyst production, suggesting that allosamidin does not affect P. berghei CHT1.
CHT1 of P. falciparum is significantly different from P. berghei CHT1, in that the P. falciparum protein does not appear to be a pro-enzyme, nor does it appear to have a chitin-binding domain.
In P. falciparum a mutant has been generated with a disrupted gene encoding pfCHT1 (Y. Tsai et al., 2001, Infect. Immun. 69, 4048-54). This mutant  had normal gametocytogenesis, exflagellation, and ookinete formation but was markedly impaired in its ability to form oocysts in Anopheles freeborni midguts.

Other mutants