WordNet

protozoa having four membranous ciliary organelles
relative of the paramecium; often used in genetics research

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/07/27 04:33:15」(JST)

wiki en

Tetrahymena are free-living ciliate protozoa that can also switch from commensalistic to pathogenic modes of survival. They are common in freshwater ponds. Tetrahymena species used as model organisms in biomedical research are T. thermophila and T. pyriformis.^[1]

Main fields of biomedical research where Tetrahymena cells are used as models

T. thermophila: a model organism in experimental biology

β-tubulin in Tetrahymena.

Tetrahymena conjugation. When nutrients are scarce, two individuals (A) pair with each other and begin sexual reproduction (conjugation). (B) The diploid micronucleus in each individual undergoes meiosis to form four haploid nuclei, and three of these are degraded. (C) The remaining haploid nucleus divides mitotically to form two pronuclei in each cell. (D) One of the two pronuclei in each cell is exchanged with the mating partner, and fusion leads to he formation of the diploid zygotic nucleus. (E) The zygotic nucleus divides twice mitotically to form four nuclei. (F) Two nuclei become micronuclei, and the other two differentiate to become macronuclei; the original parental macronucleus is degraded. (G) Cell division occurs and the nuclei are distributed to the daughter cells so that each progeny receives one micronucleus and one macronucleus.

As a ciliated protozoan, Tetrahymena thermophila exhibits nuclear dimorphism: two types of cell nuclei. They have a bigger, non-germline macronucleus and a small, germline micronucleus in each cell at the same time and they both carry out different functions with distinct cytological and biological properties. This unique versatility allows scientists to use Tetrahymena to identify several key factors regarding gene expression and genome integrity. In addition, Tetrahymena possess hundreds of cilia and has complicated microtubule structures, making it an optimal model to illustrate the diversity and functions of microtubule arrays.

Because Tetrahymena can be grown in a large quantity in the laboratory with ease, it has been a great source for biochemical analysis for years, specifically for enzymatic activities and purification of sub-cellular components. In addition, with the advancement of genetic techniques it has become an excellent model to study the gene function in vivo. The recent sequencing of the macronucleus genome should ensure that Tetrahymena will be continuously used as a model system.

Tetrahymena thermophila exists in 7 different sexes (mating types) that can reproduce in 21 different combinations, and a single tetrahymena cannot reproduce sexually with itself. Each organism "decides" which sex it will become during mating, through a stochastic process.^[2]

Studies on Tetrahymena have contributed to several scientific milestones including:

First cell which showed synchronized division, which led to the first insights into the existence of mechanisms which control the cell cycle.^[3]
Identification and purification of the first cytoskeleton based motor protein such as dynein.^[3]
Aid in the discovery of lysosomes and peroxisomes.^[3]
Early molecular identification of somatic genome rearrangement.^[3]
Discovery of the molecular structure of telomeres, telomerase enzyme, the templating role of telomerase RNA and their roles in cellular senescence and chromosome healing (for which a Nobel Prize was won).^[3]
Nobel Prize–winning co-discovery (1989, in Chemistry) of catalytic ribonucleic acid (ribozyme).^[3]
Discovery of the function of histone acetylation.^[3]
Demonstration of the roles of posttranslational modification such as acetylation and glycylation on tubulins and discovery of the enzymes responsible for some of these modifications (glutamylation)
Crystal structure of 40S ribosome in complex with its initiation factor eIF1
First demonstration that two of the "universal" stop codons, UAA and UAG, will code for the amino acid glutamine in some eukaryotes, leaving UGA as the only termination codon in these organisms. ^[4]
Discovery of self-splicing RNA. ^[5]

Life cycle

The life cycle of T. thermophila consists of an alternation of haploid and diploid stages. During vegetative growth diploid cells reproduce by binary fission. Cell division occurs by a sequence of morphogenetic events that result in the development of duplicate sets of cell structures, one for each daughter cell.

As is typical of ciliates, T. thermophila has two functionally differentiated types of nuclei, the micronucleus and macronucleus.^[6] The micronucleus is the germline nucleus; i.e., it contains the DNA information passed down from one sexual generation to the next. The micronucleus is diploid and contains five pairs of chromosomes. The genes of the micronucleus are transcriptionally inert during vegetative growth. The macronucleus is the somatic nucleus, i.e. its genes are actively expressed. However, the macronucleus is propagated only during the vegetative part of the life cycle and is not transmitted from one sexual generation to the next. The macronucleus is polyploid and contains 200–300 autonomously replicating DNA species derived from the five micronuclear chromosomes by site-specific fragmentation.

Tetrahymena can be induced to undergo conjugation by washing which causes rapid starvation.^[7] When starved, T. thermophila cells change into fast-swimming dispersal forms. When such cells of one mating type encounter cells of a complementary mating type conjugation can occur. During conjugation two cells pair, form a temporary junction and exchange gamete nuclei. They then generate and differentiate the nuclei of their sexual progeny. This process takes about 12 hours. The sequence of events during conjugation is outlined in the accompanying figure.

The Rad51 recombinase of T. thermophila is a homolog of the Escherichia coli RecA recombinase. In T. thermophila, Rad51 participates in homologous recombination during mitosis, meiosis and in the repair of double-strand breaks.^[8] During conjugation, Rad51 is necessary for completion of meiosis. Meiosis in T. thermophila appears to employ a Mus81-dependent pathway that does not use a synaptonemal complex and is considered secondary in most other model eukaryotes.^[9] This pathway includes the Mus81 resolvase and the Sgs1 helicase. The Sgs1 helicase appears to promote the non-crossover outcome of meiotic recombinational repair of DNA,^[10] a pathway that generates little genetic variation.

It is common among protists that the sexual cycle is inducible by stressful conditions such as starvation.^[11] Such conditions often cause DNA damage. A central feature of meiosis is homologous recombination between non-sister chromosomes. In T. thermophila this process of meiotic recombination may be beneficial for repairing DNA damages caused by starvation.

References

^ Elliott, Alfred M. (1973). Biology of Tetrahymena. Dowen, Hutchinson and Ross Inc. ISBN 0-87933-013-9.
^ Selecting; Segment Joining, Gene; Deletion; Cervantes, MD; Hamilton, EP; Xiong, J; Lawson, MJ; Yuan, D et al. (2013). "Selecting One of Several Mating Types through Gene Segment Joining and Deletion in Tetrahymena thermophila". PLoS Biol 11 (3): e1001518. doi:10.1371/journal.pbio.1001518.
^ ^a ^b ^c ^d ^e ^f ^g Tetrahymena Genome Sequencing White Paper
^ Horowitz S; Gorovsky M (April 1985). "An unusual genetic code in nuclear genes of Tetrahymena". Proc. Natl. Acad. Sci. USA 82 (8): 2452–2455. doi:10.1073/pnas.82.8.2452. PMC 397576. PMID 3921962.
^ Kruger, K.; Grabowski, P. J.; Zaug, A. J.; Sands, J.; Gottschling, D. E.; Cech, T. R. (1982). "Self-splicing RNA: Autoexcision and autocyclization of the ribosomal RNA intervening sequence of tetrahymena". Cell 31: 147. doi:10.1016/0092-8674(82)90414-7. edit
^ Prescott DM (June 1994). "The DNA of ciliated protozoa". Microbiol. Rev. 58 (2): 233–67. PMC 372963. PMID 8078435.
^ Elliott, AM; Hayes, RE (1953). "Mating Types in Tetrahymena". Biological Bulletin 105: 269–284. doi:10.2307/1538642.
^ Marsh, TC; Cole, ES; Stuart, KR; Campbell, C; Romero, DP (2000). "RAD51 is required for propagation of the germinal nucleus in Tetrahymena thermophila". Genetics 154 (4): 1587–1596. PMID 10747055.
^ Chi, J; Mahé, F; Loidl, J; Logsdon, J; Dunthorn, M (2014). "Meiosis gene inventory of four ciliates reveals the prevalence of a synaptonemal complex-independent crossover pathway". Mol Biol Evol 31 (3): 660–672. doi:10.1093/molbev/mst258. PMID 24336924.
^ Lukaszewicz A, Howard-Till RA, Loidl J (November 2013). "Mus81 nuclease and Sgs1 helicase are essential for meiotic recombination in a protist lacking a synaptonemal complex". Nucleic Acids Res. 41 (20): 9296–309. doi:10.1093/nar/gkt703. PMC 3814389. PMID 23935123.
^ Bernstein, Harris; Bernstein, Carol; Michod, Richard E. (2011). "19. Meiosis as an Evolutionary Adaptation for DNA Repair". In Inna Kruman. DNA Repair. InTech Open Publisher. doi:10.5772/25117.

External links

Tetrahymena Stock Center at Cornell University
ASSET: Advancing Secondary Science Education thru Tetrahymena
Tetrahymena Genome Database
Tetrahymena thermophila Genome Project at The Institute for Genomic Research
Tetrahymena thermophila Genome Sequence Synopsis
Tetrahymena thermophila genome paper
Tetrahymena experiments on Journal of Visualized Experiments (JoVE) website
Microbial Digital Specimen Archives: Tetrahymena image gallery

English Journal

A Tetrahymena Hsp90 co-chaperone promotes siRNA loading by ATP-dependent and ATP-independent mechanisms.

Woehrer SL1, Aronica L1, Suhren JH1, Busch CJ1, Noto T1, Mochizuki K2.
The EMBO journal.EMBO J.2015 Jan 14. pii: e201490062. [Epub ahead of print]
The loading of small interfering RNAs (siRNAs) and microRNAs into Argonaute proteins is enhanced by Hsp90 and ATP in diverse eukaryotes. However, whether this loading also occurs independently of Hsp90 and ATP remains unclear. We show that the Tetrahymena Hsp90 co-chaperone Coi12p promotes siRNA loa
PMID 25588944

Role of The Cytosolic Heat Shock Protein 70 Ssa5 in the Ciliate Protozoan Tetrahymena thermophila.

Fukuda Y1, Akematsu T, Attiq R, Tada C, Nakai Y, Pearlman RE.
The Journal of eukaryotic microbiology.J Eukaryot Microbiol.2015 Jan 14. doi: 10.1111/jeu.12203. [Epub ahead of print]
Heat shock protein 70 (Hsp70) is a member of a family of conserved chaperone proteins whose function is well investigated in many model organisms. Here we focus on an Hsp70 called Ssa5 in the ciliate protozoan Tetrahymena thermophila, and reveal that its translation is heat inducible as for general
PMID 25586926

Potential genotoxicity and risk assessment of a chlorinated flame retardant, Dechlorane Plus.

Dou J1, Jin Y1, Li Y1, Wu B1, Li M2.
Chemosphere.Chemosphere.2015 Jan 10. pii: S0045-6535(14)01508-2. doi: 10.1016/j.chemosphere.2014.12.066. [Epub ahead of print]
Dechlorane Plus (DP) is a chlorinated flame retardants that is globally ubiquitous. It is a potentially persistent organic pollutant (POPs) and an environmental toxin. However, the toxicity data is still limited and cannot provide a comprehensive environmental ecological risk assessment for DP. In t
PMID 25585867

Japanese Journal

Dynamic Change of Cellular Localization of Microtubule-Organizing Center During Conjugation of Ciliate Tetrahymena thermophila

Kushida Yasuharu,Takaine Masak,Nakano Kentaro [他]
Zoological science 32(1), 25-32, 2015-01
NAID 40020363740

Installation of orthogonality to the interface that assembles two modular domains in the Tetrahymena group Ⅰ ribozyme

Tanaka Takahiro,Furuta Hiroyuki,Ikawa Yoshiya
Journal of bioscience and bioengineering 117(4), 407-412, 2014-04
NAID 40020051346

Installation of orthogonality to the interface that assembles two modular domains in the Tetrahymena group I ribozyme(GENETICS, MOLECULAR BIOLOGY, AND GENE ENGINEERING)

Tanaka Takahiro,Furuta Hiroyuki,Ikawa Yoshiya
Journal of bioscience and bioengineering 117(4), 407-412, 2014-04
… Two modular elements (P5abc and ΔP5) in the Tetrahymena group I ribozyme can be separated physically to generate a two-piece ribozyme derivative consisting of a separately prepared P5abc (P5 RNA) and the rest of the intron (ΔP5 RNA). …
NAID 110009817054

Related Pictures

★リンクテーブル★

リンク元	「テトラヒメナ」「Tetrahymenina」「テトラヒメナ属」
拡張検索	「Tetrahymena属」「Tetrahymena thermophila」「Tetrahymena pyriformis」

「テトラヒメナ」

Tetrahymena
	Tetrahymena thermophila
Scientific classification
Domain:	Eukaryota
(unranked):	Alveolata
Phylum:	Ciliophora
Class:	Oligohymenophorea
Order:	Hymenostomatida
Family:	Tetrahymenidae
Genus:	Tetrahymena
Species
	T. hegewischi; T. hyperangularis; T. malaccensis; T. pigmentosa; T. pyriformis; T. thermophila; T. vorax

　　[★]

ラ: Tetrahymena
関: テトラヒメナ属、Tetrahymena属、テトラヒメナ亜目

「Tetrahymenina」

　　[★]

テトラヒメナ亜目

トラヒメナ亜目

関: Tetrahymena

「テトラヒメナ属」

　　[★]

ラ: Tetrahymena
関: テトラヒメナ、Tetrahymena属

「Tetrahymena属」

　　[★]

ラ: Tetrahymena
関: テトラヒメナ、テトラヒメナ属

「Tetrahymena thermophila」

　　[★]

テトラヒメナ・サーモフィラ

関: T. thermophila

「Tetrahymena pyriformis」

　　[★]

テトラヒメナ・ピリフォルミス

[1] Elliott, Alfred M. (1973). Biology of Tetrahymena. Dowen, Hutchinson and Ross Inc. ISBN 0-87933-013-9.

[PLOS2013-2] Selecting; Segment Joining, Gene; Deletion; Cervantes, MD; Hamilton, EP; Xiong, J; Lawson, MJ; Yuan, D et al. (2013). "Selecting One of Several Mating Types through Gene Segment Joining and Deletion in Tetrahymena thermophila". PLoS Biol 11 (3): e1001518. doi:10.1371/journal.pbio.1001518.

[whitepaper-3] ^ ^a ^b ^c ^d ^e ^f ^g Tetrahymena Genome Sequencing White Paper

[4] Horowitz S; Gorovsky M (April 1985). "An unusual genetic code in nuclear genes of Tetrahymena". Proc. Natl. Acad. Sci. USA 82 (8): 2452–2455. doi:10.1073/pnas.82.8.2452. PMC 397576. PMID 3921962.

[5] Kruger, K.; Grabowski, P. J.; Zaug, A. J.; Sands, J.; Gottschling, D. E.; Cech, T. R. (1982). "Self-splicing RNA: Autoexcision and autocyclization of the ribosomal RNA intervening sequence of tetrahymena". Cell 31: 147. doi:10.1016/0092-8674(82)90414-7. edit

[pmid8078435-6] Prescott DM (June 1994). "The DNA of ciliated protozoa". Microbiol. Rev. 58 (2): 233–67. PMC 372963. PMID 8078435.

[7] Elliott, AM; Hayes, RE (1953). "Mating Types in Tetrahymena". Biological Bulletin 105: 269–284. doi:10.2307/1538642.

[8] Marsh, TC; Cole, ES; Stuart, KR; Campbell, C; Romero, DP (2000). "RAD51 is required for propagation of the germinal nucleus in Tetrahymena thermophila". Genetics 154 (4): 1587–1596. PMID 10747055.

[9] Chi, J; Mahé, F; Loidl, J; Logsdon, J; Dunthorn, M (2014). "Meiosis gene inventory of four ciliates reveals the prevalence of a synaptonemal complex-independent crossover pathway". Mol Biol Evol 31 (3): 660–672. doi:10.1093/molbev/mst258. PMID 24336924.

[pmid23935123-10] Lukaszewicz A, Howard-Till RA, Loidl J (November 2013). "Mus81 nuclease and Sgs1 helicase are essential for meiotic recombination in a protist lacking a synaptonemal complex". Nucleic Acids Res. 41 (20): 9296–309. doi:10.1093/nar/gkt703. PMC 3814389. PMID 23935123.

[11] Bernstein, Harris; Bernstein, Carol; Michod, Richard E. (2011). "19. Meiosis as an Evolutionary Adaptation for DNA Repair". In Inna Kruman. DNA Repair. InTech Open Publisher. doi:10.5772/25117.

匿名

検索

案内

案内

Tetrahymena