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Division of Cell Biology and Imaging, Department of Radiology

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Cell Biology | Cells


Background: 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. 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.

Methods: Phenotypes of the RNAi depletions were characterized by immunofluorescence (IF), electron microscopy, and mass spectrometry.

Results: We 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.

Conclusions: Silencing 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.


Basal body, Cilia, RNAi, Striated rootlet

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© The Author(s) 2019. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

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Nabi A, Yano J, Valentine MS, Picariello T, Van Houten JL. SF-Assemblin genes in Paramecium: phylogeny and phenotypes of RNAi silencing on the ciliary-striated rootlets and surface organization. Cilia. 2019 Oct 29;8:2. doi: 10.1186/s13630-019-0062-y. PMID: 31673332; PMCID: PMC6819543. Link to article on publisher's site

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Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.