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Li H, Wu K, Feng Y, Gao C, Wang Y, Zhang Y, Pan J, Shen X, Zufall RA, Zhang Y, Zhang W, Sun J, Ye Z, Li W, Lynch M, Long H. Integrative analyses on the ciliates Colpoda illuminate the life history evolution of soil microorganisms. mSystems 2024:e0137923. [PMID: 38819204 DOI: 10.1128/msystems.01379-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Accepted: 03/04/2024] [Indexed: 06/01/2024] Open
Abstract
Microorganisms play a central role in sustaining soil ecosystems and agriculture, and these functions are usually associated with their complex life history. Yet, the regulation and evolution of life history have remained enigmatic and poorly understood, especially in protozoa, the third most abundant group of organisms in the soil. Here, we explore the life history of a cosmopolitan species-Colpoda steinii. Our analysis has yielded a high-quality macronuclear genome for C. steinii, with size of 155 Mbp and 37,123 protein-coding genes, as well as mean intron length of ~93 bp, longer than most other studied ciliates. Notably, we identify two possible whole-genome duplication events in C. steinii, which may account for its genome being about twice the size of C. inflata's, another co-existing species. We further resolve the gene expression profiles in diverse life stages of C. steinii, which are also corroborated in C. inflata. During the resting cyst stage, genes associated with cell death and vacuole formation are upregulated, and translation-related genes are downregulated. While the translation-related genes are upregulated during the excystment of resting cysts. Reproductive cysts exhibit a significant reduction in cell adhesion. We also demonstrate that most genes expressed in specific life stages are under strong purifying selection. This study offers a deeper understanding of the life history evolution that underpins the extraordinary success and ecological functions of microorganisms in soil ecosystems.IMPORTANCEColpoda species, as a prominent group among the most widely distributed and abundant soil microorganisms, play a crucial role in sustaining soil ecosystems and promoting plant growth. This investigation reveals their exceptional macronuclear genomic features, including significantly large genome size, long introns, and numerous gene duplications. The gene expression profiles and the specific biological functions associated with the transitions between various life stages are also elucidated. The vast majority of genes linked to life stage transitions are subject to strong purifying selection, as inferred from multiple natural strains newly isolated and deeply sequenced. This substantiates the enduring and conservative nature of Colpoda's life history, which has persisted throughout the extensive evolutionary history of these highly successful protozoa in soil. These findings shed light on the evolutionary dynamics of microbial eukaryotes in the ever-fluctuating soil environments. This integrative research represents a significant advancement in understanding the life histories of these understudied single-celled eukaryotes.
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Affiliation(s)
- Haichao Li
- Key Laboratory of Evolution and Marine Biodiversity (Ministry of Education), Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, Shandong Province, China
- Laboratory for Marine Biology and Biotechnology, Qingdao Marine Science and Technology Center, Qingdao, Shandong Province, China
| | - Kun Wu
- Key Laboratory of Evolution and Marine Biodiversity (Ministry of Education), Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, Shandong Province, China
| | - Yuan Feng
- Key Laboratory of Evolution and Marine Biodiversity (Ministry of Education), Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, Shandong Province, China
| | - Chao Gao
- Key Laboratory of Evolution and Marine Biodiversity (Ministry of Education), Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, Shandong Province, China
| | - Yaohai Wang
- Key Laboratory of Evolution and Marine Biodiversity (Ministry of Education), Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, Shandong Province, China
| | - Yuanyuan Zhang
- Key Laboratory of Evolution and Marine Biodiversity (Ministry of Education), Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, Shandong Province, China
| | - Jiao Pan
- Key Laboratory of Evolution and Marine Biodiversity (Ministry of Education), Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, Shandong Province, China
| | - Xiaopeng Shen
- College of Life Sciences, Anhui Normal University, Wuhu, Anhui Province, China
| | - Rebecca A Zufall
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, USA
| | - Yu Zhang
- School of Mathematics Science, Ocean University of China, Qingdao, Shandong Province, China
| | - Weipeng Zhang
- Key Laboratory of Evolution and Marine Biodiversity (Ministry of Education), Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, Shandong Province, China
| | - Jin Sun
- Key Laboratory of Evolution and Marine Biodiversity (Ministry of Education), Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, Shandong Province, China
| | - Zhiqiang Ye
- School of Life Sciences, Central China Normal University, Wuhan, Hubei Province, China
| | - Weiyi Li
- Department of Genetics, Stanford University School of Medicine, Stanford, California, USA
| | - Michael Lynch
- Biodesign Center for Mechanisms of Evolution, Arizona State University, Tempe, Arizona, USA
| | - Hongan Long
- Key Laboratory of Evolution and Marine Biodiversity (Ministry of Education), Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, Shandong Province, China
- Laboratory for Marine Biology and Biotechnology, Qingdao Marine Science and Technology Center, Qingdao, Shandong Province, China
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2
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Shimada M, Hayakawa MM, Suzaki T, Ishida H. Morphological reconstruction during cell regeneration in the ciliate Spirostomum ambiguum. Eur J Protistol 2024; 94:126079. [PMID: 38593565 DOI: 10.1016/j.ejop.2024.126079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 03/21/2024] [Accepted: 03/26/2024] [Indexed: 04/11/2024]
Abstract
When the ciliate Spirostomum ambiguum is transected into two pieces, both fragments regenerate and proliferate. In the anterior fragments, which have lost their contractile vacuoles due to transection, new contractile vacuoles were formed at their posterior ends in a few minutes. When the cells were cut into three pieces, new contractile vacuoles were formed in the anterior and middle fragments, both at their posterior ends. Thus, the anterior-posterior axis of S. ambiguum was maintained after transection. Morphological repair, including the formation of the contractile vacuole, was also observed when only the anteriormost portion was transected to cut out a small fragment that did not contain part of the macronucleus. Scanning electron microscopy was performed to observe changes in the shape of the cleavage surface of S. ambiguum during the wound healing process. Within minutes after cutting, the cut surface was covered with a cilia-free membrane, preventing leakage of cytoplasmic contents. The surface of the cut area then rounded with time and was covered with cilia, completing the repair of the cut area in about one day.
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Affiliation(s)
- Maho Shimada
- Graduate School of Natural Science and Technology, Shimane University, 1060 Nishikawatsu-cho, Matsue 690-8504, Japan
| | - Masashi M Hayakawa
- Graduate School of Human Sciences, Osaka University, 1-2 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Toshinobu Suzaki
- Department of Biology, Graduate School of Science, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan
| | - Hideki Ishida
- Graduate School of Natural Science and Technology, Shimane University, 1060 Nishikawatsu-cho, Matsue 690-8504, Japan.
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3
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Lee C, Maier W, Jiang YY, Nakano K, Lechtreck KF, Gaertig J. Global and local functions of the Fused kinase ortholog CdaH in intracellular patterning in Tetrahymena. J Cell Sci 2024; 137:jcs261256. [PMID: 37667859 PMCID: PMC10565251 DOI: 10.1242/jcs.261256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Accepted: 08/29/2023] [Indexed: 09/06/2023] Open
Abstract
Ciliates assemble numerous microtubular structures into complex cortical patterns. During ciliate division, the pattern is duplicated by intracellular segmentation that produces a tandem of daughter cells. In Tetrahymena thermophila, the induction and positioning of the division boundary involves two mutually antagonistic factors: posterior CdaA (cyclin E) and anterior CdaI (Hippo kinase). Here, we characterized the related cdaH-1 allele, which confers a pleiotropic patterning phenotype including an absence of the division boundary and an anterior-posterior mispositioning of the new oral apparatus. CdaH is a Fused or Stk36 kinase ortholog that localizes to multiple sites that correlate with the effects of its loss, including the division boundary and the new oral apparatus. CdaH acts downstream of CdaA to induce the division boundary and drives asymmetric cytokinesis at the tip of the posterior daughter. CdaH both maintains the anterior-posterior position of the new oral apparatus and interacts with CdaI to pattern ciliary rows within the oral apparatus. Thus, CdaH acts at multiple scales, from induction and positioning of structures on the cell-wide polarity axis to local organelle-level patterning.
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Affiliation(s)
- Chinkyu Lee
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
| | - Wolfgang Maier
- Bioinformatics, University of Freiburg, 79110 Freiburg, Germany
| | - Yu-Yang Jiang
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
| | - Kentaro Nakano
- Degree Programs in Biology, Graduate School of Science and Technology, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan
| | - Karl F. Lechtreck
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
| | - Jacek Gaertig
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
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Albright AR, Angeles-Albores D, Marshall W. Genome-wide analysis of anterior-posterior mRNA localization in Stentor coeruleus reveals a role for the microtubule cytoskeleton. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.09.523364. [PMID: 36711710 PMCID: PMC9882060 DOI: 10.1101/2023.01.09.523364] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Cells have complex and beautiful structures that are important for their function, but understanding the molecular mechanisms that produce these structures is a challenging problem due to the gap in size scales between molecular interactions and cellular structures. The giant ciliate Stentor coeruleus is a unicellular model organism whose large size, reproducible structure, and ability to heal wounds and regenerate has historically allowed the formation of structure in a single cell to be addressed using methods of experimental embryology. Such studies have shown that specific cellular structures, such as the oral apparatus, always form in specific regions of the cell, which raises the question: what is the source of positional information within this organism? By analogy with embryonic development, in which localized mRNA is often used to mark position, we asked whether position along the anterior-posterior axis of Stentor might be marked by specific regionalized mRNAs. By physically bisecting cells and conducting half-cell RNA sequencing, we were able to identify sets of messages enriched in either the anterior or posterior half. We repeated this analysis in cells in which a set of longitudinal microtubule bundles running down the whole length of the cell, known as KM-fibers, were disrupted by RNAi of b-tubulin. We found that many messages either lost their regionalized distribution or switched to an opposite distribution, such that anterior-enriched messages in control became posterior-enriched in the RNAi cells, or vice versa. This study indicates that mRNA can be regionalized within a single giant cell and that microtubules may play a role, possibly by serving as tracks for the movement of the messages.
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Affiliation(s)
- Ashley R. Albright
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA
- Center for Cellular Construction, University of California, San Francisco, San Francisco, CA, USA
| | | | - Wallace Marshall
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA
- Center for Cellular Construction, University of California, San Francisco, San Francisco, CA, USA
- Twitter: @WallaceUCSF
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5
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Echigoya S, Sato K, Kishida O, Nakagaki T, Nishigami Y. Switching of behavioral modes and their modulation by a geometrical cue in the ciliate Stentor coeruleus. Front Cell Dev Biol 2022; 10:1021469. [PMID: 36393838 PMCID: PMC9663998 DOI: 10.3389/fcell.2022.1021469] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 10/17/2022] [Indexed: 08/14/2023] Open
Abstract
Protists ubiquitously live in nature and play key roles in the food web chain. Their habitats consist of various geometrical structures, such as porous media and rigid surfaces, affecting their motilities. A kind of protist, Stentor coeruleus, exhibits free swimming and adhering for feeding. Under environmental and culture conditions, these organisms are often found in sediments with complex geometries. The determination of anchoring location is essential for their lives. However, the factors that induce the behavioral transition from swimming to adhering are still unknown. In this study, we quantitatively characterized the behavioral transitions in S. coeruleus and observed the behavior in a chamber with dead ends made by a simple structure mimicking the environmental structures. As a result, the cell adheres and feeds in narrow spaces between the structure and the chamber wall. It may be reasonable for the organism to hide itself from predators and capture prey in these spaces. The behavioral strategy for the exploration and exploitation of spaces with a wide variety of geometries in their habitats is discussed.
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Affiliation(s)
- Syun Echigoya
- Graduate School of Life Science, Hokkaido University, Sapporo, Japan
| | - Katsuhiko Sato
- Graduate School of Life Science, Hokkaido University, Sapporo, Japan
- Research Institute for Electronic Science, Hokkaido University, Sapporo, Japan
| | - Osamu Kishida
- Field Science Center for Northern Biosphere, Tomakomai Experimental Forest, Hokkaido University, Tomakomai, Japan
| | - Toshiyuki Nakagaki
- Graduate School of Life Science, Hokkaido University, Sapporo, Japan
- Research Institute for Electronic Science, Hokkaido University, Sapporo, Japan
| | - Yukinori Nishigami
- Graduate School of Life Science, Hokkaido University, Sapporo, Japan
- Research Institute for Electronic Science, Hokkaido University, Sapporo, Japan
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6
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Paul R, Zhang KS, Kurosu Jalil M, Castaño N, Kim S, Tang SKY. Hydrodynamic dissection of Stentor coeruleus in a microfluidic cross junction. LAB ON A CHIP 2022; 22:3508-3520. [PMID: 35971861 DOI: 10.1039/d2lc00527a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Stentor coeruleus, a single-cell ciliated protozoan, is a model organism for wound healing and regeneration studies. Despite Stentor's large size (up to 2 mm in extended state), microdissection of Stentor remains challenging. In this work, we describe a hydrodynamic cell splitter, consisting of a microfluidic cross junction, capable of splitting Stentor cells in a non-contact manner at a high throughput of ∼500 cells per minute under continuous operation. Introduction of asymmetry in the flow field at the cross junction leads to asymmetric splitting of the cells to generate cell fragments as small as ∼8.5 times the original cell size. Characterization of cell fragment viability shows reduced 5-day survival as fragment size decreases and as the extent of hydrodynamic stress imposed on the fragments increases. Our results suggest that cell fragment size and composition, as well as mechanical stress, play important roles in the long-term repair of Stentor cells and warrant further investigations. Nevertheless, the hydrodynamic splitter can be useful for studying phenomena immediately after cell splitting, such as the closure of wounds in the plasma membrane which occurs on the order of 100-1000 seconds in Stentor.
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Affiliation(s)
- Rajorshi Paul
- Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA.
| | - Kevin S Zhang
- Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA.
| | - Myra Kurosu Jalil
- Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA.
| | - Nicolas Castaño
- Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA.
| | - Sungu Kim
- Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA.
| | - Sindy K Y Tang
- Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA.
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7
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Sood P, Lin A, Yan C, McGillivary R, Diaz U, Makushok T, Nadkarni A, Tang SKY, Marshall WF. Modular, cascade-like transcriptional program of regeneration in Stentor. eLife 2022; 11:80778. [PMID: 35924891 PMCID: PMC9371601 DOI: 10.7554/elife.80778] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2022] [Accepted: 08/04/2022] [Indexed: 11/15/2022] Open
Abstract
The giant ciliate Stentor coeruleus is a classical model system for studying regeneration and morphogenesis in a single cell. The anterior of the cell is marked by an array of cilia, known as the oral apparatus, which can be induced to shed and regenerate in a series of reproducible morphological steps, previously shown to require transcription. If a cell is cut in half, each half regenerates an intact cell. We used RNA sequencing (RNAseq) to assay the dynamic changes in Stentor’s transcriptome during regeneration, after both oral apparatus shedding and bisection, allowing us to identify distinct temporal waves of gene expression including kinases, RNA -binding proteins, centriole biogenesis factors, and orthologs of human ciliopathy genes. By comparing transcriptional profiles of different regeneration events, we identified distinct modules of gene expression corresponding to oral apparatus regeneration, posterior holdfast regeneration, and recovery after wounding. By measuring gene expression after blocking translation, we show that the sequential waves of gene expression involve a cascade mechanism in which later waves of expression are triggered by translation products of early-expressed genes. Among the early-expressed genes, we identified an E2F transcription factor and the RNA-binding protein Pumilio as potential regulators of regeneration based on the expression pattern of their predicted target genes. RNAi-mediated knockdown experiments indicate that Pumilio is required for regenerating oral structures of the correct size. E2F is involved in the completion of regeneration but is dispensable for earlier steps. This work allows us to classify regeneration genes into groups based on their potential role for regeneration in distinct cell regeneration paradigms, and provides insight into how a single cell can coordinate complex morphogenetic pathways to regenerate missing structures.
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Affiliation(s)
- Pranidhi Sood
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States
| | - Athena Lin
- Department of Biochemistry and BioPhysics, University of California, San Francisco, San Francisco, United States
| | - Connie Yan
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States
| | - Rebecca McGillivary
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States
| | - Ulises Diaz
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States
| | - Tatyana Makushok
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States
| | - Ambika Nadkarni
- Department of Mechanical Engineering, Stanford University, palo alto, United States
| | - Sindy K Y Tang
- Department of Mechanical Engineering, Stanford University, Palo Alto, United States
| | - Wallace F Marshall
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States
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8
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Lin A, Piehowski PD, Tsai CF, Makushok T, Yi L, Diaz U, Yan C, Summers D, Sood P, Smith RD, Liu T, Marshall WF. Determining protein polarization proteome-wide using physical dissection of individual Stentor coeruleus cells. Curr Biol 2022; 32:2300-2308.e4. [PMID: 35447087 PMCID: PMC9133221 DOI: 10.1016/j.cub.2022.03.078] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 03/08/2022] [Accepted: 03/30/2022] [Indexed: 12/18/2022]
Abstract
Cellular components are non-randomly arranged with respect to the shape and polarity of the whole cell.1-4 Patterning within cells can extend down to the level of individual proteins and mRNA.5,6 But how much of the proteome is actually localized with respect to cell polarity axes? Proteomics combined with cellular fractionation7-11 has shown that most proteins localize to one or more organelles but does not tell us how many proteins have a polarized localization with respect to the large-scale polarity axes of the intact cell. Genome-wide localization studies in yeast12-15 found that only a few percent of proteins have a localized position relative to the cell polarity axis defined by sites of polarized cell growth. Here, we describe an approach for analyzing protein distribution within a cell with a visibly obvious global patterning-the giant ciliate Stentor coeruleus.16,17 Ciliates, including Stentor, have highly polarized cell shapes with visible surface patterning.1,18 A Stentor cell is roughly 2 mm long, allowing a "proteomic dissection" in which microsurgery is used to separate cellular fragments along the anterior-posterior axis, followed by comparative proteomic analysis. In our analysis, 25% of the proteome, including signaling proteins, centrin/SFI proteins, and GAS2 orthologs, shows a polarized location along the cell's anterior-posterior axis. We conclude that a large proportion of all proteins are polarized with respect to global cell polarity axes and that proteomic dissection provides a simple and effective approach for spatial proteomics.
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Affiliation(s)
- Athena Lin
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Paul D Piehowski
- Biological Science Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Chia-Feng Tsai
- Biological Science Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Tatyana Makushok
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Lian Yi
- Biological Science Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Ulises Diaz
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Connie Yan
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Diana Summers
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Pranidhi Sood
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Richard D Smith
- Biological Science Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Tao Liu
- Biological Science Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Wallace F Marshall
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA; Chan Zuckerberg Biohub, San Francisco, CA 94158, United States of America.
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Cole E, Gaertig J. Anterior-posterior pattern formation in ciliates. J Eukaryot Microbiol 2022; 69:e12890. [PMID: 35075744 PMCID: PMC9309198 DOI: 10.1111/jeu.12890] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Revised: 01/06/2022] [Accepted: 01/17/2022] [Indexed: 11/29/2022]
Abstract
As single cells, ciliates build, duplicate, and even regenerate complex cortical patterns by largely unknown mechanisms that precisely position organelles along two cell‐wide axes: anterior–posterior and circumferential (left–right). We review our current understanding of intracellular patterning along the anterior–posterior axis in ciliates, with emphasis on how the new pattern emerges during cell division. We focus on the recent progress at the molecular level that has been driven by the discovery of genes whose mutations cause organelle positioning defects in the model ciliate Tetrahymena thermophila. These investigations have revealed a network of highly conserved kinases that are confined to either anterior or posterior domains in the cell cortex. These pattern‐regulating kinases create zones of cortical inhibition that by exclusion determine the precise placement of organelles. We discuss observations and models derived from classical microsurgical experiments in large ciliates (including Stentor) and interpret them in light of recent molecular findings in Tetrahymena. In particular, we address the involvement of intracellular gradients as vehicles for positioning organelles along the anterior‐posterior axis.
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Affiliation(s)
- Eric Cole
- Biology Department, St. Olaf College, Northfield, MN, USA
| | - Jacek Gaertig
- Department of Cellular Biology, University of Georgia, Athens, GA, USA
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