Mutant/mutation
The mutant lacks expression of kinesin-8B

Protein (function)
Kinesins are molecular motor proteins that have essential roles in intracellular transport, cell division, and motility. Some kinesin families are known to contribute to the ciliary structure and function, either by transporting ciliary components along axonemal  microtubules (MTs) by IFT such as kinesin-2s, or by destabilizing MTs, such as kinesin-9 and kinesin-13. Kinesin-8s are conserved from protozoa to mammals, and can be subclassified as kinesin-8A, -8B and -8X. In general, kinesin-8s are multitasking motors, able to move along MTs, cross-link and slide MTs, and influence MT dynamics at their ends.  Kinesin-8As are best characterised as regulators of spindle length and chromosome positioning during metaphase, whereas the mammalian kinesin-8B (Kif19) has a role in ciliary length control. The Plasmodium genome encodes two kinesin-8s (kinesin-8X and kinesin-8B), along with six or seven other kinesin proteins. Kinesin-8X is conserved across the Apicomplexa, whereas kinesin-8B is restricted to certain genera such as Toxoplasma, Eimeria, and Plasmodium that have flagellated gametes. 
Kinesin-8B is specifically expressed in male gametocytes/gametes.

Phenotype
Normal asexual blood stage growth/multiplication. Strongly reduced male gamete formation/exflagellation. 

Additional information
IFAs performed during the course of male gametogenesis evidenced a re-organization of α-tubulin II in WT and ΔPbkin8B mutant to assemble microtubules in the cytoplasm rolling around the nucleus at 2, 8 and 12 min post induction. From 12 min post induction, the replicated DNA separated into ‘clumps’ in WT. In mutants, DNA reorganized but did not individualize into distinguishable clumps, even at 15 min post induction. At these times, the overall cell shape differed between mutant and WT parasites. ΔPbkin8B male gametocytes remained rounded, whereas WT gametocytes started exflagellating. Protrusions labelled with the anti α‐tubulin II antibody and corresponding to male gametes could be seen in WT cells, but not in ΔPbkin8B mutants. Even after 30 min post induction, only few exflagellations were recorded in mutants and no male gamete release was observed by IFA. WT and ΔPbkin8B male gametocytes were examined by electron microscopy to further examine the effects of the mutation. At 15 min post induction, WT male gametocytes appeared spherical in shape and exhibited an enlarged nucleus in which multiple nuclear pores could be identified, while the cytoplasm containing a number of axonemes. Frequently, an electron dense basal body was associated with the nuclear pole and gave rise to an axoneme. In cross section, a number, but not all, of the axonemes showed the characteristic 9+2 microtubular organization. In contrast, while a number of mutant male gametocytes appeared spherical, others appeared more flattened (data not shown). When examined at higher magnification, the cytoplasm was seen to contain large numbers of elongated, randomly orientated doublet and single microtubules. There was no evidence of any coordination of the microtubules to form 9+2 axonemes. In addition, there appeared to be fewer nuclear poles and basal bodies present in the mutant parasites. 

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