Flagellum assembly in protozoan parasites

The cell cycle is fundamental for Leishmania survivability and to maintain pathogenicity, ensuring that each generation retains the same cytoskeletal morphology and organelles. This requires a tightly coordinated process of organelle duplication and segregation at specific stages. Using volume electron microscopy, we reconstructed Leishmania mexicana promastigote cells at different cell cycle stages, to produce a 3D view of organelle positioning and division. Our findings show that the new flagellum does not rotate around the old flagellum and cytokinesis creates a membrane indentation that is retained in daughter cells until early in the next cell cycle. Transition fibres serve as docking sites for axonemal proteins, ensuring proper flagellum assembly and length maintenance. In Leishmania, flagella elongate over multiple cell cycles, and we identified CEP164C as a regulator of flagellum growth, instead of as part of a locking mechanism. We observed CEP164C localising to the old flagellum and being recruited to the new flagellum later in the cell cycle. Knockdown of CEP164C caused dysregulation, with the old flagellum elongating and the new one shortening. In T. brucei, CEP164C localizes exclusively to the old flagellum. We investigated whether CEP164C interacts with differentially expressed transition fibre proteins found at the old and new flagella. Our findings showed that knockdown of CEP164C results in the upregulation of four of these transition fibre proteins. We also studied gametogenesis in Plasmodium berghei which occurs in the Anopheles mosquito and is critical for sexual reproduction and transmission to mammalian hosts. Using volume electron microscopy, we examined key structures in P. berghei microgametocytes and microgametes. Our findings revealed axonemes coiling around the nucleus in opposite directions, forming a central axonemal band. We also discovered that the nucleus tightly coils around the axoneme in microgametes before exflagellation. This detailed 3D organisation of flagellated microgametes provides new insights into the mechanisms of axoneme assembly and haploid genome organisation in malaria parasites.

Grantor dc:publisher

Oxford Brookes University

Author dc:creator

• Hair, Molly

Contributors dc:contributor

• Vaughan, Sue
• Sunter, Jack

Statement dc:rights

• All rights reserved

Language dc:language

en

DOI dc:identifier

https://doi.org/10.24384/gmyq-j850

OAI identifier oai:identifier

tle:83201132-e653-4403-939c-c4542ffe0876:d6bd9758-527a-46cd-bfe2-c433766e8fca:1