-
The Journal of Protozoology 1991Ciliates exhibit nuclear dimorphism, i.e. they have a germline micronucleus and a somatic macronucleus. Macronuclei are differentiated from mitotic sisters of... (Review)
Review
Ciliates exhibit nuclear dimorphism, i.e. they have a germline micronucleus and a somatic macronucleus. Macronuclei are differentiated from mitotic sisters of micronuclei. The macronuclei of "higher ciliates" are polyploid and divide acentromerically ("amitotically"); they differentiate once per life cycle. By contrast, Karyorelict (KR) ciliate macronuclei are nearly diploid and cannot divide; they must differentiate at every cell cycle. Diverse lines of evidence are presented to support the hypothesis that ancestral ciliate macronuclei were incapable of division (as in living karyorelict ciliates) and that higher ciliates gained, perhaps independently more than once, the ability to divide the macronucleus. Selective pressures that could have driven the evolution and macronuclear division and two plausible step-wise pathways for the evolution of macronuclear division are proposed. These hypotheses are relevant to our understanding of amitosis mechanisms, evolution of nuclear dimorphism, and phylogenetic classification of ciliates.
Topics: Animals; Biological Evolution; Cell Nucleus; Ciliophora; Mitosis
PubMed: 1908902
DOI: 10.1111/j.1550-7408.1991.tb04431.x -
The International Journal of... Feb 1996In the course of macronuclear development of the hypotrichous ciliates all genetic information not required for normal growth of the cell is removed from the new... (Review)
Review
In the course of macronuclear development of the hypotrichous ciliates all genetic information not required for normal growth of the cell is removed from the new macronucleus. This differentiation process involves DNA-splicing, excision of transposons, DNA-fragmentation, selective gene amplification and telomere addition. Since many of the processes observed during macronuclear development, such as DNA-transposition, DNA-rearrangement or selective DNA-amplification, may occur in differentiating cells of higher organisms, this biological system provides an unusual opportunity to study the ways in which DNA-sequences can be manipulated in a differentiating cell.
Topics: Animals; Cell Nucleus; Ciliophora; DNA Fragmentation; DNA Transposable Elements; DNA, Protozoan
PubMed: 8735923
DOI: No ID Found -
Journal of Genetics Jun 2015
Review
Origin, structure and function of millions of chromosomes present in the macronucleus of unicellular eukaryotic ciliate, Oxytricha trifallax: a model organism for transgenerationally programmed genome rearrangements.
Topics: Chromosomes; Gene Rearrangement; Genome, Protozoan; Inheritance Patterns; Macronucleus; Models, Biological; Oxytricha
PubMed: 26174664
DOI: 10.1007/s12041-015-0504-2 -
European Journal of Protistology Feb 2022Zinc finger MYND-type containing 10 (ZMYND10) or BLU is a putative tumor suppressor that inhibits the proliferation of nasopharyngeal carcinoma cells by regulating the...
Zinc finger MYND-type containing 10 (ZMYND10) or BLU is a putative tumor suppressor that inhibits the proliferation of nasopharyngeal carcinoma cells by regulating the cell cycle. On the other hand, some recent studies have also found that ZMYND10 is a ciliary protein that is essential for ciliary structure and function and is mutated in primary ciliary dyskinesia (PCD). Our recent study shows that ZMYND10 is essential for ciliary growth and structure in Paramecium tetraurelia. The results in the current work continually reveal that depletion of ZMYND10 interrupted the process of amitotic macronucleus division in Paramecium. Immunostaining showed that the microtubular backbone of dividing macronucleus disintegrated in cells without ZMYND10. Furthermore, a transcriptomic analysis and RT-qPCR revealed the differential expression of some genes, including DYHA, DYHB, kinesin, kinesin-like proteins and Ran-GTP in ZMYND10-depleted cells, in accordance with their roles in regulating cilia and macronucleus division.
Topics: Cell Cycle; Cilia; Cytoskeletal Proteins; Macronucleus; Paramecium; Paramecium tetraurelia
PubMed: 35065333
DOI: 10.1016/j.ejop.2021.125863 -
Genome Research Mar 2020The somatic macronucleus (MAC) and germline micronucleus (MIC) of differ in chromosome numbers, sizes, functions, transcriptional activities, and cohesin complex...
The somatic macronucleus (MAC) and germline micronucleus (MIC) of differ in chromosome numbers, sizes, functions, transcriptional activities, and cohesin complex location. However, the higher-order chromatin organization in is still largely unknown. Here, we explored the higher-order chromatin organization in the two distinct nuclei of using the Hi-C and HiChIP methods. We found that the meiotic crescent MIC has a specific chromosome interaction pattern, with all the telomeres or centromeres on the five MIC chromosomes clustering together, respectively, which is also helpful to identify the midpoints of centromeres in the MIC. We revealed that the MAC chromosomes lack A/B compartments, topologically associating domains (TADs), and chromatin loops. The MIC chromosomes have TAD-like structures but not A/B compartments and chromatin loops. The boundaries of the TAD-like structures in the MIC are highly consistent with the chromatin breakage sequence (CBS) sites, suggesting that each TAD-like structure of the MIC chromosomes develops into one MAC chromosome during MAC development, which provides a mechanism of the formation of MAC chromosomes during conjugation. Overall, we demonstrated the distinct higher-order chromatin organization in the two nuclei of the and suggest that the higher-order chromatin structures may play important roles during the development of the MAC chromosomes.
Topics: Centromere; Chromatin; Chromosomes; Macronucleus; Meiosis; Micronucleus, Germline; Tetrahymena thermophila
PubMed: 32165395
DOI: 10.1101/gr.241687.118 -
Cells Nov 2021Nuclear autophagy is an important selective autophagy process. The selective autophagy of sexual development micronuclei (MICs) and the programmed nuclear degradation of...
Nuclear autophagy is an important selective autophagy process. The selective autophagy of sexual development micronuclei (MICs) and the programmed nuclear degradation of parental macronucleus (paMAC) occur during sexual reproduction in . The molecular regulatory mechanism of nuclear selective autophagy is unclear. In this study, the autophagy-related protein Atg5 was identified from . Atg5 was localized in the cytoplasm in the early sexual-development stage and was localized in the paMAC in the late sexual-development stage. During this stage, the degradation of meiotic products of MIC was delayed in mutants. Furthermore, paMAC was abnormally enlarged and delayed or failed to degrade. The expression level and lipidation of Atg8.2 significantly decreased in the mutants. All these results indicated that Atg5 was involved in the regulation of the selective autophagy of paMAC by regulating Atg8.2 in
Topics: Acids; Autophagy; Autophagy-Related Protein 5; Gene Knockdown Techniques; Macronucleus; Meiosis; Models, Biological; Mutation; Protozoan Proteins; Reproduction; Tetrahymena thermophila
PubMed: 34831293
DOI: 10.3390/cells10113071 -
Biochemical Genetics Jun 1972
Review
Topics: Animals; Base Sequence; Cell Nucleus; Ciliophora; DNA; Genes; Genetics, Microbial; Paramecium; Tetrahymena pyriformis
PubMed: 4199804
DOI: 10.1007/BF00486122 -
The Journal of Eukaryotic Microbiology Jan 2018The intraflagellar transport IFT57 protein is essential for ciliary growth and maintenance. Also known as HIPPI, human IFT57 can be translocated to the nucleus via a...
The intraflagellar transport IFT57 protein is essential for ciliary growth and maintenance. Also known as HIPPI, human IFT57 can be translocated to the nucleus via a molecular partner of the Huntingtin, Hip1, inducing gene expression changes. In Paramecium tetraurelia, we identified four IFT57 genes forming two subfamilies IFT57A/B and IFT57C/D arising from whole genome duplications. The depletion of proteins of the two subfamilies induced ciliary defects and IFT57A and IFT57C localized in basal bodies and cilia. We observed that IFT57A, but not IFT57C, is also present in the macronucleus and able to traffic toward the developing anlage during autogamy. Analysis of chimeric IFT57A-IFT57C-GFP-tagged proteins allowed us to identify a region of IFT57A necessary for nuclear localization. We studied the localization of the unique IFT57 protein of Paramecium caudatum, a species, which diverged from P. tetraurelia before the whole genome duplications. The P. caudatumIFT57C protein was excluded from the nucleus. We also analyzed whether the overexpression of IFT57A in Paramecium could affect gene transcription as the human protein does in HeLa cells. The expression of some genes was indeed affected by overexpression of IFT57A, but the set of affected genes poorly overlaps the set of genes affected in human cells.
Topics: Adaptor Proteins, Signal Transducing; Amino Acid Sequence; Genes, Protozoan; Macronucleus; Multigene Family; Paramecium tetraurelia; Protozoan Proteins; Sequence Alignment
PubMed: 28474836
DOI: 10.1111/jeu.12423 -
The Journal of Eukaryotic Microbiology Jul 2022Amitosis is widespread among eukaryotes, but the underlying mechanisms are poorly understood. The polyploid macronucleus (MAC) of unicellular ciliates divides by...
Amitosis is widespread among eukaryotes, but the underlying mechanisms are poorly understood. The polyploid macronucleus (MAC) of unicellular ciliates divides by amitosis, making ciliates a potentially valuable model system to study this process. However, a method to accurately quantify the copy number of MAC chromosomes has not yet been established. Here, we used droplet digital PCR (ddPCR) to quantify the absolute copy number of the MAC chromosomes in Tetrahymena thermophila. We first confirmed that ddPCR is a sensitive and reproducible method to determine accurate chromosome copy numbers at the single-cell level. We then used ddPCR to determine the copy number of different MAC chromosomes by analyzing individual T. thermophila cells in the G1 and the amitotic (AM) phases. The average copy number of MAC chromosomes was 90.9 at G1 phase, approximately half the number at AM phase (189.8). The copy number of each MAC chromosome varied among individual cells in G1 phase and correlated with cell size, suggesting that amitosis accompanied by unequal cytokinesis causes copy number variability. Furthermore, the fact that MAC chromosome copy number is less variable among AM-phase cells suggests that the copy number is standardized by regulating DNA replication. We also demonstrated that copy numbers differ among different MAC chromosomes and that interchromosomal variations in copy number are consistent across individual cells. Our findings demonstrate that ddPCR can be used to model amitosis in T. thermophila and possibly in other ciliates.
Topics: Chromosomes; Ciliophora; DNA Copy Number Variations; Humans; Macronucleus; Polyploidy; Tetrahymena; Tetrahymena thermophila
PubMed: 35313044
DOI: 10.1111/jeu.12907 -
Cold Spring Harbor Protocols Jan 2010
Topics: DNA; Genetic Complementation Test; Genetic Techniques; Genome; Green Fluorescent Proteins; Macronucleus; Microinjections; Paramecium; RNA Interference; Recombination, Genetic; Transgenes
PubMed: 20150123
DOI: 10.1101/pdb.prot5364