Abstract
Ciliated protozoa are characterized by generative micronuclei and vegetative polyploid macronuclei. Micronuclei of Stylonychia mytilus contain 1 600 times as much DNA per haploid genome as E. coli. Most of this DNA is shown to be repetitive. The development of the macronucleus involves, as demonstrated by cytology, only 1/3 of the chromosomes which in a first replication phase are polytenized in probably 5 replication steps and appear as giant chromosomes. At this developmental stage considerable amounts of repetitive DNA are still present in the chromosomes. During the subsequent disintegration phase more than 90% of the DNA are eliminated from the macronucleus anlage. The remainder is further replicated five times and composes the final macronucleus. Since this DNA reassociates with a reaction rate almost identical to an ideal second order reaction its kinetic complexity can be determined by comparison with the kinetic complexity of E. coli DNA. Macronuclear DNA reassociates with a kinetic complexity of 26 times the kinetic complexity of E. coli DNA (corrected for GC content) which indicates that macronuclear DNA sequences exist at a ploidy level of 4 096 C. We assume that macronuclear DNA may be present only once per haploid genome. In this case it represents only 1.6% of the DNA in micronuclei or 10% of the DNA in the giant chromosome stage.
Similar content being viewed by others
References
Ammermann, D.: Cytologische und genetische Untersuchungen an dem Ciliaten Stylonychia mytilus Ehrenberg. Arch. Protistenk. 108, 109–152 (1965)
Ammermann, D.: Release of DNA breakdown products into the culture medium of Stylonychia mytilus exconjugants (Protozoa, Ciliata) during the destruction of the polytene chromosomes. J. Cell Biol. 40, 576–577 (1969)
Ammermann, D.: Morphology and development of the macronuclei of the ciliates Stylonychia mytilus and Euplotes aediculatus. Chromosoma (Berl.) 33, 209–238 (1971)
Beermann, S.: A quantitative study of chromatin diminution in embryonic mitoses of Cyclops furcifer. Genetics 54, 567–576 (1966)
Bostock, C. J., Prescott, D. M.: Evidence of gene diminution during the formation of the macronueleus in the protozoan Stylonychia. Proc. nat. Acad. Sci. (Wash.) 69, 139–142 (1972)
Britten, R. J., Davidson, E. H.: Recent studies on moderately repetitive DNA sequences. Molec. gen. and develop. Biol. (M. Sussman, ed.), p. 5–27 (1972)
Britten, R. J., Kohne, D. E.: Repeated sequences in DNA. Science 161, 529–540 (1968)
Britten, R. J., Waring, M.: “Renaturation” of the DNA of higher organisms. Carnegie Inst. Wash. Year Book 64, 316–333 (1965)
Flamm, W. G.: Highly repetitive sequences of DNA in chromosomes. Int. Rev. Cytol. 32, 1–51 (1972)
Gil, R., Alonso, P., Perez-Silva, J.: Ultrastructure of the macronuclear anlage in Stylonychia mytilus. Exp. Cell Res. 72, 509–518 (1972)
Hennig, W.: Highly repetitive DNA sequences in the genome of Drosophila hydei. I. Preferential localization in the X chromosomal heterochromatin. J. molec. Biol. 71, 407–417 (1872a)
Hennig, W.: Highly repetitive DNA sequences in the genome of Drosophila hydei II. Occurence in polytene tissues. J. molec. Biol. 71, 419–431 (1972b)
Hennig, W.: Molecular hybridisation of DNA and RNA in situ. Int. Rev. Cytol. 36, 1–44 (1973)
Hennig, W., Hennig, I., Stein, H.: Repeated sequences in the DNA of Drosophila and their localisation in giant chromosomes. Chromosoma (Berl.) 32, 31–63 (1970)
Kleinschmidt, A.: Methods in enzymology, vol. 2, (L. Grossman and K. Moldave, eds.), p. 36. New York: Academic Press 1968
Kleinschmidt, A., Zahn, R. K.: Über Desoxyribonucleinsäure-Molekeln in Protein-Mischfilmen. Z. Naturforsch. 14b, 770–779 (1959)
Kloetzel, J. A.: Compartmentalization of the developing macronucleus following conjugation in Stylonychia and Euplotes. J. Cell Biol. 47, 395–407 (1970)
Murti, K. G., Prescott, D. M., Péne, J. J.: DNA of ciliated Protozoa. III. Binding of RNA polymerase and denaturation at the ends of the low molecular weight DNA in Stylonychia. J. molec. Biol. 68, 413–416 (1972)
Prescott, D. M., Bostock, C. J., Murti, K. G., Lauth, M. R., Gamow, E.: DNA of ciliated Protozoa. I. Electron microscopic and sedimentation analyses of macronuclear and micronuclear DNA of Stylonychia mytilus. Chromosoma (Berl.) 34, 355–366 (1971)
Rae, P. M. M.: The distribution of repetitive DNA sequences in chromosomes. Advanc. cell. mol. Biol. 2, 109–149 (1972)
Rae, P. M. M.: 5-Hydroxymethylaracyil in the DNA of the dinoflagellate. Proc. nat. Acad. Sci. (Wash.) 70, 1141–1145 (1973)
Rao, M. V. N., Ammermann, D.: Polytene chromosomes and nucleic acid metabolism during macronuclear development in Euplotes. Chromosoma (Berl.) 29, 240–254 (1970)
Studier, F. W.: Sedimentation studies of the size and shape of DNA. J. molec. Biol. 11, 373–390 (1965)
Walker, P. M. B.: “Repetitive” DNA in higher organisms. Progr. biophys. molec. Biol. 23, 149–190 (1971)
Wetmur, J. G., Davidson, N.: Kinetics of renaturation of DNA. J. molec. Biol. 31, 349–370 (1968)
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Ammermann, D., Steinbrück, G., von Berger, L. et al. The development of the macronucleus in the ciliated protozoan Stylonychia mytilus . Chromosoma 45, 401–429 (1974). https://doi.org/10.1007/BF00283386
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00283386