Preparation of Chromosomes of Tetrahymena Pyriformis for Photomicrography

Ray, Charles

doi:10.3109/10520295609113817

Cited by 8 publications

(7 citation statements)

References 6 publications

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“…During asexual reproduction, the MAC divides amitotically, with apparently random distribution of chromosome copies that behave as if acentromeric. In contrast, MIC chromosomes are metacentric [ 32 ] and are distributed mitotically [ 33 , 34 ]. Parental MAC DNA is not transmitted to sexual progeny, although it does have an epigenetic influence on postzygotic MAC genome rearrangement, mediated by RNA interference [ 35 ].…”

Section: Introductionmentioning

confidence: 99%

Macronuclear Genome Sequence of the Ciliate Tetrahymena thermophila, a Model Eukaryote

Eisen¹,

Coyne²,

Wu³

et al. 2006

PLoS Biol

703

721

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The ciliate Tetrahymena thermophila is a model organism for molecular and cellular biology. Like other ciliates, this species has separate germline and soma functions that are embodied by distinct nuclei within a single cell. The germline-like micronucleus (MIC) has its genome held in reserve for sexual reproduction. The soma-like macronucleus (MAC), which possesses a genome processed from that of the MIC, is the center of gene expression and does not directly contribute DNA to sexual progeny. We report here the shotgun sequencing, assembly, and analysis of the MAC genome of T. thermophila, which is approximately 104 Mb in length and composed of approximately 225 chromosomes. Overall, the gene set is robust, with more than 27,000 predicted protein-coding genes, 15,000 of which have strong matches to genes in other organisms. The functional diversity encoded by these genes is substantial and reflects the complexity of processes required for a free-living, predatory, single-celled organism. This is highlighted by the abundance of lineage-specific duplications of genes with predicted roles in sensing and responding to environmental conditions (e.g., kinases), using diverse resources (e.g., proteases and transporters), and generating structural complexity (e.g., kinesins and dyneins). In contrast to the other lineages of alveolates (apicomplexans and dinoflagellates), no compelling evidence could be found for plastid-derived genes in the genome. UGA, the only T. thermophila stop codon, is used in some genes to encode selenocysteine, thus making this organism the first known with the potential to translate all 64 codons in nuclear genes into amino acids. We present genomic evidence supporting the hypothesis that the excision of DNA from the MIC to generate the MAC specifically targets foreign DNA as a form of genome self-defense. The combination of the genome sequence, the functional diversity encoded therein, and the presence of some pathways missing from other model organisms makes T. thermophila an ideal model for functional genomic studies to address biological, biomedical, and biotechnological questions of fundamental importance.

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Section: Introductionmentioning

confidence: 99%

Macronuclear Genome Sequence of the Ciliate Tetrahymena thermophila, a Model Eukaryote

Eisen¹,

Coyne²,

Wu³

et al. 2006

PLoS Biol

703

721

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“…He called my attention to an abstract on the chromosome number of four varieties of Tetrahymena (Ray and Elliott 1954). There followed a series of papers see Ray (1956a, b). One of the advantages of the Fixative is that chromosomes are disposed in a single plane (Ray and Elliott 1954).…”

Section: Epiloguementioning

confidence: 99%

“…One of the advantages of the Fixative is that chromosomes are disposed in a single plane (Ray and Elliott 1954). This is especially useful in photomicrography (Ray 1956b). He had started using the Fixative in the protozoology course at Emory University (pers.…”

Section: Epiloguementioning

confidence: 99%

“…Various stains have been used following fixation. The most frequent appear to be aceto‐carmine (Ray 1956a, 1956b), acid fuchsin (Napolitano, Wall, and Ganz 1970), Feulgen reaction (Chen, Luo, and Cao 1982; Ron and Suhr‐Jessen 1981; Wee 1983), Giemsa (Culbertson 1981), hematoxylin (Ron and Suhr‐Jessen 1981; Willumsen 1982), Kernechtrot (Willumsen, Siemensma, and Suhr‐Jessen 1987), methyl green and pyronin (Kovalchuk 1980), NMF (Borror 1969), and protargol method (Borror 1962, 1966, 1968b; Read et al 1983; Shyam and Sarma 1975). With regard to the Feulgen reaction, Golikova et al (1980) studied the intensity of the reaction in macro‐ and micronuclei of Paramecium bursaria under various conditions of hydrolysis and age of the organism.…”

Section: Epiloguementioning

confidence: 99%

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Behind the Discovery of “Nissenbaum's Fixative”

Nissenbaum¹

2001

J Eukaryotic Microbiology

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The author describes the serendipitous discovery, conception, development, and history of Nissenbaum's Fixative while an undergraduate biology major in the early 1950s. The subsequent uses, applications, and modifications over the past forty-seven years are also described. Some of the modifications omitted from his short original paper are mentioned. Highlights of his subsequent career in the field of medicine are noted.

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“…Tetrahymena , like other ciliated protozoa, contains two types of nuclei, a large, highly polyploid macronucleus that regulates the ongoing metabolism of the cell, and divides by amitosis, and a smaller diploid micronucleus that divides by mitosis with each cell doubling (Orias et al, 2011; Karrer, 2012). The micronucleus is also capable of meiosis, the first step of which is its elongation (Ray, 1956a; Sugai and Hiwatashi, 1974). During vegetative growth gene expression is not detected from the micronucleus (Mayo and Orias, 1981), and it is metabolically inactive (Gorovsky and Woodard, 1969).…”

Section: Introductionmentioning

confidence: 99%

Colchicine-induced degeneration of the micronucleus during conjugation in Tetrahymena

et al. 2014

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One of the most dramatic examples of nuclear morphogenesis occurs during conjugation in Tetrahymena when the micronucleus elongates to a size longer than the cell itself. After contraction to a spherical shape, the nucleus moves directly to chromosome separation in the first meiotic division. Here we investigate the consequences of interrupting the elongation process. Colchicine, a microtubule inhibitor, caused retraction of elongated structures. With time, cells began to lose their micronuclei, and by five hours more than half of the paired cells had at least one cell missing a micronucleus. After reversing the colchicine block, existing micronuclei did not undergo elongation again, nor did meiosis occur. These observations indicate that micronuclear elongation is critical to subsequent meiotic division. Further, nuclear elimination occurs, which could be due to meiotic failure or possibly a problem downstream from meiosis. An analysis of the process of colchicine-induced micronuclear degeneration indicated that it was regulated by a caspase-dependent mechanism, characteristic of apoptosis, and then resorbed by a lysosome-dependent autophagic mechanism. Amicronucleate cells failed to grow when returned to nutrient medium, likely because of a lesion in the post-conjugation reconstruction of a functioning oral apparatus. The ease by which a large number of nuclei are induced to “self-destruct” may make this system useful in investigating the link between colchicine treatment and nuclear death in Tetrahymena, and in investigating how nuclear death could be regulated in living cells more generally. Finally, we note that this phenomenon might relate to the evolution of amicronucleate species of Tetrahymena.

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Preparation of Chromosomes of Tetrahymena Pyriformis for Photomicrography

Cited by 8 publications

References 6 publications

Macronuclear Genome Sequence of the Ciliate Tetrahymena thermophila, a Model Eukaryote

Macronuclear Genome Sequence of the Ciliate Tetrahymena thermophila, a Model Eukaryote

Behind the Discovery of “Nissenbaum's Fixative”

Colchicine-induced degeneration of the micronucleus during conjugation in Tetrahymena

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