Basal body movements orchestrate membrane organelle division and cell morphogenesis inTrypanosoma brucei

Abstract

SummaryThe defined shape and single-copy organelles of Trypanosoma brucei mean that it provides an excellent model in which to study how duplication and segregation of organelles is interfaced with morphogenesis of overall cell shape and form. The centriole or basal body of eukaryotic cells is often seen to be at the centre of such processes. We have used a combination of electron microscopy and electron tomography techniques to provide a detailed three-dimensional view of duplication of the basal body in trypanosomes. We show that the basal body duplication and maturation cycle exerts an influence on the intimately associated flagellar pocket membrane system that is the portal for secretion and uptake from this cell. At the start of the cell cycle, a probasal body is positioned anterior to the basal body of the existing flagellum. At the G1-S transition, the probasal body matures, elongates and invades the pre-existing flagellar pocket to form the new flagellar axoneme. The new basal body undergoes a spectacular anti-clockwise rotation around the old flagellum, while its short new axoneme is associated with the pre-existing flagellar pocket. This rotation and subsequent posterior movements results in division of the flagellar pocket and ultimately sets parameters for subsequent daughter cell morphogenesis.

Polo-like kinase is necessary for flagellum inheritance in Trypanosoma brucei

“…To more clearly identify this tendrillar projection, extracted cells were labeled with antiTbPLK antibodies, negatively stained, and then visualized by electron microscopy (EM). In dividing cells, the new MtQ is initiated on the anterior side of the new basal body (Lacomble et al, 2010). At early stages of the cell cycle the new MtQ was labeled with TbPLK in a pattern similar to that seen using immunofluorescence ( Fig.…”

“…The first stage of this process is maturation of the probasal body, which gains the capacity to nucleate a new flagellum (Lacomble et al, 2010). This maturation can be tracked with antibodies against trypanosome basal body component (TBBC) protein, a coiled coil protein shown to associate selectively with mature basal bodies (Dilbeck et al, 1999;Absalon et al, 2008).…”

“…Flagellum biogenesis is initiated by the maturation of the probasal body, which triggers growth of a new flagellum alongside the existing one (Fig. 1B, I) (Sherwin and Gull, 1989;Lacomble et al, 2010). Once it reaches the flagellar pocket neck, this needs to duplicate, so that each flagellar pocket now contains an emergent flagellum.…”

A coiled-coil- and C2-domain-containing protein is required for FAZ assembly and cell morphology in Trypanosoma brucei

“…The flagellar pocket region also appeared normal in CC2D RNAi cells. Previous reports suggested that a new flagellum and a new FAZ play important roles in flagellar pocket organization, basal body positioning and segregation (Absalon et al, 2008;Kohl et al, 2003;Lacomble et al, 2010). Whereas elongation of the new flagellum, with its distal end anchored to the old flagellum, pushes the new basal body away to the posterior end of the cell, the new FAZ might restrain the segregation and hold the new basal body in place.…”

“…The mature basal body seeds the growth of the flagellum. The pro-basal body, initially constructed anterior to the mature basal body, migrates to the posterior side of the mature basal body upon maturation, thus allowing the construction of a new flagellum posterior to the old flagellum (Lacomble et al, 2010). The basal bodies also physically link to the kinetoplast (aggregated mitochondrial DNA) and drive kinetoplast division during the cell cycle (Ogbadoyi et al, 2003;.…”