Mutant/mutation
The mutant lacks expression of CDPK4 (and is drug-selectable marker free).

Protein (function)
CDPK4 belongs to an expanded family of Ca²⁺ dependent protein kinases (CDPKs). CDPKs combine an amino-terminal serine/threonine kinase domain and a carboxy-terminal calmodulin-like domain, composed of four EF hands, in the same molecule. In plants, CDPKs translate Ca²⁺ signals generated by external stimuli into cellular responses, thereby regulating cell division and differentiation, the development of tolerance to stress stimuli and the specific defense responses to pathogens.

CDPK4 plays a role in male gamete formation after activation of male gametes. It plays a role in male gametocytes axoneme formation, formation of mitotic spindles and DNA synthesis. Evidence has been presented for an additional role in sporozoites: reduced invasion of hepatocytes (RMgm-1510).  See PF3D7_0717500 for other CDPK4 mutants

Phenotype
No male gametes are formed after activation of male gametocytes (no exflagellation).
Through analysis of a number of mutants expressing mutated CDPK4 proteins, combined with inhibitor studies, evidence is presented for the following: 'CDPK4 controls three processes essential to progress from a single haploid microgametocyte to the release of eight flagellated microgametes in Plasmodium berghei. A myristoylated isoform is activated by Ca2+ to initiate a first genome replication within twenty seconds of activation. This role is mediated by a protein of the SAPS-domain family involved in S-phase entry. At the same time, CDPK4 is required for the assembly of the subsequent mitotic spindle and to phosphorylate a microtubule-associated protein important for mitotic spindle formation. Finally, a non-myristoylated isoform is essential to complete cytokinesis by activating motility of the male flagellum. This role has been linked to phosphorylation of an uncharacterised flagellar protein. 

Additional information

Other mutants
See PF3D7_0717500 for other CDPK4 mutants