Mutant/mutation
The mutant expresses a N-terminal FLAG-0tagged version of Actin II

Protein (function)
Actins are filament-forming, highly-conserved proteins in eukaryotes. They are involved in essential processes in the cytoplasm and have also nuclear functions. Malaria parasites (Plasmodium spp.) have two actin isoforms that differ from each other and from canonical actins in structure and filament-forming properties. Actin I has an essential role in motility and is fairly well characterized. The structure and function of actin II are not as well understood, but mutational analyses have revealed two essential functions in male gametogenesis and in the zygote. The protein is highly expressed in male gametes/gametocytes.

Phenotype
Western blot analysis of flag::actII extracts of purified samples from mixed blood stages, activated gametocytes, and zygotes. Actin II expression was highly upregulated after induction of gamete formation (gametogenesis). The protein was weakly expressed in mature female gametes, and its amount increased in zygotes. These results are consistent with previous genetic analysis, which showed that male gamete formation was abolished in mutants lacking actin II while maternal/female expression of actin II in the zygote stage is strictly required for the development of the oocyst stage.
In extracts of dissected mosquito midguts containing oocysts (harvested 3 and 10 d post blood feeding) analyzed by Western blot, no signal was detected. 

Additional information
Immunolabeling using the anti-FLAG antibody to detect actin II was carried out in different stages of the parasite. Male gametocytes showed a dynamic actin II signal. In non-activated gametocytes, the protein was seen mainly in the nucleus, although a weaker signal was also detected in the cytoplasm, 0 min sample). Later (4 min post activation), its expression was restricted to the nucleus, as revealed by the overlap with DNA. 8 min after activation, the protein was localized in the periphery of the nucleus as long rods in some cells or as dots or very short rods in others. This pattern was seen in a minority of the cells observed (~10%), suggesting that the protein is only briefly present in the rod-like structures. In exflagellating males, the protein was localized in the residual cell with no signal in the flagellar male gamete. In female gametocytes, actin II was not detected, consistent with the results from the Western blot and our previous results]. Localization of FLAG::actinII was also investigated in zygotes. In zygotes, two patterns were seen. Most samples showed diffuse actin II in the nucleus. In rare samples, the protein was localized in rods associated with the nucleus. This may  suggest that transient filaments are formed during zygote maturation. In ookinetes, no signal was detected, consistent with the Western blot analysis. 

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