Mutant/mutation
The mutant lacks expression of DOZI (protein development of zygote inhibited; ATP-dependent RNA helicase, putative) and expresses GFP under control of a male and RFP under control of a female gametocyte specific promoter.

Protein (function)
DOZI is an RNA helicase that is highly up-regulated in female gametocytes and shows high sequence homology to the DDX6 family of RNA helicases.  It contains domains involved in RNA-binding and RNA-unwinding activity.  In other eukaryotes the DDX6 family of DEAD-box RNA helicases is tightly linked both to storage of mRNAs encoding proteins associated with progression through meiosis into translationally silent mRNPs and with the transport of mRNA to degradation centers in the cell (P-bodies). These helicases are found in organisms as diverse as yeast (e.g., Dhh1p) and humans (e.g., RCK/p54).

Phenotype
The phenotype analyses indicate an essential role of DOZI in the development of fertilized female gametes (zygotes).
The phenotype analyses indicate that DOZI has a central role in the silencing and maintenance of steady-state levels of a population of gametocyte-specific transcripts. The loss of DOZI severely affected the capacity of the parasite to store and stabilize a discrete subset of mRNAs in the female gametocyte, resulting in a failure to synthesize specific proteins and to complete normal zygote development.  Translational repression of transcripts encoding these proteins in Plasmodium may function to specifically regulate gene expression during meiosis in the zygote.

Additional information
The dozi gene has been disrupted in a reporter line (RMgm-164) expressing GFP under control of a male and RFP under control of a female gametocyte specific promoter. This reporter line mutant can used to determine fertilisation of female gametes and meiosis in zygotes by FACS analysis. Female gametes/zygotes express RFP allowing for FACS selection of the RFP-positive females to be analysed. Before FACS analysis live cells are stained with the DNA specific dye Hoechst 32258 to measure DNA content and determine the ploïdy of female cells by FACS analysis (Ponzi, M. et al., 2009, Cell. Microbiol 11, 1272-88).

DOZI is also produced in male gametocytes, although in much lower abundance than in females. Male and female gametes of pbdozi^– have been crossed with gametes of mutant parasite lines that are defective in male or in female gamete production (see RMgm-100). These cross-fertilization assays revealed that male pbdozi^– gametes were able to fertilize wild-type DOZI-expressing female gametes, resulting in the development of ookinetes. By contrast, development of zygotes from pbdozi^– females fertilized by wild-type males was incomplete and similar to development of zygotes from the pbdozi^– line. These crosses demonstrate that the block in zygote/ookinete development is essentially due to a lack of DOZI of female gametocyte origin.

Other mutants
RMgm-100: P. berghei ANKA cl15cy1 mutant lacking expression of DOZI (protein development of zygote inhibited; ATP-dependent RNA helicase, putative)
RMgm-133: P. berghei ANKA cl15cy1mutant that expresses a c-terminally GFP-tagged version of DOZI