Mutant/mutation
The mutant lacks expression of cell division cycle protein 20 homolog, putative (CDC20/CDH1).

Protein (function)
During eukaryotic mitosis anaphase and mitotic exit is regulated by the conserved multi-subunit E3 ubiquitin ligase Anaphase Promoting Complex/Cyclosome (APC/C), which targets mitotic regulators such as securin and cyclin B for destruction by the 26S proteosome. Two of the major regulators of APC/C activity are cell-division cycle protein 20 (CDC20) (also known as Fizzy, p55CDC or Slp1) and its homologue, CDC20 homologue 1 (CDH1 – also known as Cdh1p/Hct1p, Fizzy-related, Ste9, Srw1 or Ccs52). CDC20 and CDH1 are related tryptophan-aspartic acid (WD)-40 repeat- containing adaptor proteins, which are highly conserved throughout eukaryotic evolution. CDC20 protein accumulates during S-phase, peaks in mitosis and activates the phosphorylated APC/C complex (which is phosphorylated by cyclin-dependent kinase 1 (CDK1) and other mitotic kinases by physical association, which results in the activation of the metaphase-anaphase transition and degradation of mitotic cyclins via ubiquitination.
Sequence analyses of P. berghei identified a cdc20 gene (PBANKA_051060) comprised of one exon. The protein contains a classical KEN-box, RVL-cyclin binding motif, IR motif and seven WD-40 repeat motifs as found in CDC20 and CDH1 of other organisms, but does not contain a C-box, D-box or a Mad2-interacting motif. Only a single CDC20/CDH1 homologue was identified in diferent Plasmodium species.

Phenotype
Normal numbers of gametocytes are formed. Male gametocytes fail to form gametes (exflagellate). Female gametocytes produce fertile female gametes (as shown by cross-fertilisation with wild-type male gametes). Evidence is presented that genome replication in the activated male gametocytes (for formation of the 8 haploid male gametes) and formation of axonemes is not affected. Ultrastructural analyses provided evidence for a lack of  chromosome condensation and 'aborted' nuclear spindle kinetochore formation.

Additional information
Analyses of mutants expressing C-terminally GFP-tagged CDC20 provided evidence for expression of CDC20 in nuclei of all blood stages (asexual and sexual) with upregulation in nuclei of male gametocytes.

Other mutants
RMgm-744: a mutant in which the endogenous cdc20 is C-terminally tagged with GFP
RMgm-745: a mutant expressing  GFP-tagged CDC20 episomally (using the same plasmid utilized to target the endogenous locus described in RMgm-744) under control of the cdc20 promoter