Paramecium tetraurelia basal body structure

Abstract

Paramecium is a free-living unicellular organism, easy to cultivate, featuring ca. 4000 motile cilia emanating from longitudinal rows of basal bodies anchored in the plasma membrane. The basal body circumferential polarity is marked by the asymmetrical organization of its associated appendages. The complex basal body plus its associated rootlets forms the kinetid. Kinetids are precisely oriented within a row in correlation with the cell polarity. Basal bodies also display a proximo-distal polarity with microtubule triplets at their proximal ends, surrounding a permanent cartwheel, and microtubule doublets at the transition zone located between the basal body and the cilium. Basal bodies remain anchored at the cell surface during the whole cell cycle. On the opposite to metazoan, there is no centriolar stage and new basal bodies develop anteriorly and at right angle from the base of the docked ones. Ciliogenesis follows a specific temporal pattern during the cell cycle and both unciliated and ciliated docked basal bodies can be observed in the same cell. The transition zone is particularly well organized with three distinct plates and a maturation of its structure is observed during the growth of the cilium. Transcriptomic and proteomic analyses have been performed in different organisms including Paramecium to understand the ciliogenesis process. The data have incremented a multi-organism database, dedicated to proteins involved in the biogenesis, composition and function of centrosomes, basal bodies or cilia. Thanks to its thousands of basal bodies and the well-known choreography of their duplication during the cell cycle, Paramecium has allowed pioneer studies focusing on the structural and functional processes underlying basal body duplication. Proteins involved in basal body anchoring are sequentially recruited to assemble the transition zone thus indicating that the anchoring process parallels the structural differentiation of the transition zone. This feature offers an opportunity to dissect spatio-temporally the mechanisms involved in the basal body anchoring process and transition zone formation.

Cell chirality: its origin and roles in left–right asymmetric development

“…The ciliary structure, called the ciliary unit, is positioned in the cell cortex in an asymmetric and polarized (right-handed) manner [7,10]. The ciliary unit is centred over a complex protein structure called the basal body [11,12] (figure 2, right). To examine how polarity forms in ciliates, experimental manipulations were performed to induce atypical ciliary row structures.…”

“…The basal body at the base of the cilium and cytoskeletal appendages (called the ciliary rootlet and microtubule ribbon) make up the cortical unit (figure 2, right) [7,11,12]. The ciliary rootlet normally extends in an anterior direction, and on the right side of the basal body and the cell (figure 2, right).…”

Evolutionary Cell Biology of Proteins from Protists to Humans and Plants

“…; Tassin et al. ). Nevertheless, in ciliates, the alter ego of basal bodies, the centriole, does not contain any centrin (Hodges et al.…”

Multiple phosphorylation sites on γ‐tubulin are essential and contribute to the biogenesis of basal bodies in Tetrahymena

“…To explore this phenotype further, we stained S129D-overexpressing cells to detect the markers of BB orientation and maturity. Within the locomotory rows of wild-type cells, the BBs are uniformly oriented in regard to their intrinsic chirality (reviewed in Bayless, Galati, & Pearson, 2016;Beisson & Jerka-Dziadosz, 1999;Tassin, Lemullois, & Aubusson-Fleury, 2016). Each BB within the row (with the exception of the most anterior BB of the pair at the apical crown, Jerka-Dziadosz, 1981) is accompanied by a non-microtubular structure, the kinetodesmal fiber, and two types of microtubule bundles (postciliary and transverse microtubules) whose proximal ends are consistently at the same circumferential positions on the BB (Allen, 1969).…”