Mutant/mutation
The mutant expresses a C-terminal GFP-tagged version of cell division cycle protein 20 homolog, putative (CDC20/CDH1). The endogenous cdc20 gene is tagged with GFP.

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.

P. berghei mutants lacking CDC20/CDH1 (RMgm-746) showed a normal multiplication of the asexual blood stages and normal production of gametocytes. However, male gametocytes fail to form gametes (exflagellate), whereas 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.

Phenotype
P. berghei mutants lacking CDC20/CDH1 (RMgm-746) showed a normal multiplication of the asexual blood stages and normal production of gametocytes. However, male gametocytes fail to form gametes (exflagellate), whereas 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.

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.

Additional information

Other mutants
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
RMgm-746: A mutant lacking expression of CDC20