Vital role for Plasmodium berghei Kinesin8B in axoneme assembly during male gamete formation and mosquito transmission [article]

D. Depoix, S.R. Marques, D.J.P. Ferguson, S. Chaouch, T. Duguet, R.E. Sinden, P. Grellier, L. Kohl
2019 bioRxiv   pre-print
SummarySexual development is an essential phase in the Plasmodium life cycle, where male gametogenesis is an original and extraordinarily rapid process. It produces 8 haploid motile microgametes, from a microgametocyte within 15 minutes. Its unique achievement lies in linking the assembly of 8 axonemes in the cytoplasm to the three rounds of intranuclear genome replication, forming motile microgametes, which are in a process called exflagellation. Surprisingly little is known about the actors
more » ... about the actors involved in this process. We were interested in kinesins, molecular motors that could play potential roles in male gametogenesis. We have undertaken a functional characterization in Plasmodium berghei of a kinesin identified in male gametocytes and gametes, kinesin-8B (PbKIN8B). By generating Pbkin8B-gfp parasites, we show that PbKIN8B is specifically expressed during male gametogenesis and is associated with the axoneme. We created a ΔPbkin8B knockout cell line and analysed the consequences of absence of PbKIN8B on male gametogenesis. In ΔPbkin8B knockout cells, microtubule based motility is not affected in asexual mitoses and motility in the merozoite/ookinete similar to wild type cells. We show that the ability to produce sexually differentiated gametocytes is not affected in ΔPbkin8B parasites and that the 3 rounds of genome replication occurred normally. Nevertheless, the development to free motile microgametes was halted and the life cycle was interrupted in vivo. Ultrastructural analysis revealed that intranuclear mitoses were unaffected whereas cytoplasmic microtubules although assembled in doublets and elongated, failed to assemble in the normal axonemal "9+2" structure and become motile. Absence of a functional axoneme prevented microgamete assembly and release from the microgametocyte, severely reducing infection of the mosquito vector. This is the first functional study of a kinesin involved in male gametogenesis. Taken together, these results confirm a previously unknown role for PbKIN8B in male gametogenesis, providing new insights into Plasmodium flagellar organization.
doi:10.1101/664375 fatcat:gr25gxmxlfbc5ia4etl33rkfuu