Abstract
BackgroundCilia emanate from basal bodies just underneath the cell membrane. Basal bodies must withstand torque from the ciliary beat and be appropriately spaced for cilia to beat in metachronal waves. Basal body rootlets provide stability for motile cilia. Paramecium has three. Our focus is on the largest one, the striated rootlet (SR). Paramecium basal bodies align in straight rows. Previously we found a potential role for the SR in this alignment. Here we present a phylogeny of the Paramecium homologs of the SF-Assemblin gene of the SR of Chlamydomonas, and the organization of these genes. We describe the phenotypes from RNA interference (RNAi) silencing of genes and gene groups.MethodsPhenotypes of the RNAi depletions were characterized by immunofluorescence (IF), electron microscopy, and mass spectrometry.ResultsWe found 30 genes for Paramecium SF-Assemblin homologs (SFA) organized into 13 Paralog Groups (further categorized in five Structural Groups). Representatives of Paralog Groups were found in the SRs. Silencing the transcripts of any of the Structural Groups correlates with misaligned rows of basal bodies, SRs, and cortical units. The silencing of Structural Groups was key and gave us the ability to systematically disrupt SR structures and cell surface organization.ConclusionsSilencing of SFA genes and Paralog Groups shows no effects on the SR or the cell surface organization. Silencing of the larger Structural Groups has an enormous impact on rows of basal bodies, SRs and cortical units, and SR striations, and length. Misaligned basal bodies have cilia causing the cells to swim in abnormal paths.
Highlights
Cilia emanate from basal bodies just underneath the cell membrane
For Tetrahymena, the authors found that ciliary force is necessary and sufficient to misalign basal bodies in dis-A1 mutant cells and that normally basal body rotation out of alignment is resisted by the striated rootlet (SR). It appears that the basal bodies dock at the surface and have all three rootlets emanating at normal angles in the Structural Group-depleted cells
We found that the depletion of Structural Groups led to the dramatic phenotypes of loss of basal body row orientation, cortical unit organization, and the SR shape, striations and length
Summary
Cilia emanate from basal bodies just underneath the cell membrane. Basal bodies must withstand torque from the ciliary beat and be appropriately spaced for cilia to beat in metachronal waves. We focus here on motile cilia, which allow cells like Paramecium to swim in their watery environment of a pond or stream and to sense and respond to their environment [2]. These cilia share many proteins across phyla, which is why the green algae, Chlamydomonas. While there can be microtubule-based appendages at the basal body, there usually is at least one striated rootlet (SR) composed of proteins unrelated to tubulin This SR ( known as a kinetodesmal fiber, KF in protists) links the cilium to the cell body.
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