A pair of large centrosomal proteins are crucial for daughter cell formation in Toxoplasma gondii.

Toxoplasma gondii fast replication is key to its pathogenesis in intermediate hosts such as humans. The centrosome is central to the organization and coordination of the cell cycle and division of these parasites. One of the main roles of the centrosome is to ensure proper positioning and production of the daughter cell scaffold. Daughter cell assembly is a complex process that is regulated at distance by the centrosome through the nucleation of a fiber that is visible by electron microscopy. However, the centrosome components involved are poorly described. To gain novel insights into the biology and the composition of the T. gondii centrosome, we identified and characterized TgCep404 and TgCep359, two proteins associated with the centrosome, which dynamically elongate towards the apical pole of the forming daughter cells. TgCep404 and TgCep359 interact with each other, playing an essential role in the survival of the parasite. Combined depletion of these proteins leads to the disorganization of the daughter cell inner membrane complex and disruption of the normal cell cycle. It also affects the division and segregation of the centrosome. We propose that TgCep404 and TgCep359 could form a structure that positions the apical plaque of the IMC in the budding daughter cells, hence explaining its essential role in the construction of the daughter cell IMC.