Skip to main content
NCBI home page
Proceedings of the National Academy of Sciences of the United States of America logoLink to Proceedings of the National Academy of Sciences of the United States of America
. 1988 Jul;85(14):5156–5160. doi: 10.1073/pnas.85.14.5156

Molecular evidence for somatic recombination in the ribosomal DNA of Tetrahymena thermophila.

A Løvlie 1, B L Haller 1, E Orias 1
PMCID: PMC281707  PMID: 2899324

Abstract

The ribosomal DNA (rDNA) in Tetrahymena thermophila is a 21-kilobase-pair palindromic DNA molecule that replicates autonomously in the macronucleus and is maintained at the level of about 10,000 copies per macronucleus. The rDNA of inbred strain C3 outreplicates the rDNA of inbred strain B in most B/C3 heterozygous macronuclei, generating macronuclei containing exclusively C3 rDNA sequences. In 1% or less of the B/C3 heterozygous macronuclei, however, rDNA sequences derived from both B and C3 strains persist in the macronucleus (co-maintainers). We report here that long-term culture of co-maintainers has yielded recombinant rDNA molecules combining sequences from both parental inbred strains. The genetic structure of such molecules also gives us virtual certainty that the differential replication of C3 rDNA with respect to B rDNA is due to the DNA sequence difference previously reported in domain 2 of the rDNA replication regions of the two strains.

Full text

PDF
5156

Images in this article

5158Image
on p.5158
5159Image
on p.5159

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Bruns P. J., Katzen A. L., Martin L., Blackburn E. H. A drug-resistant mutation in the ribosomal DNA of Tetrahymena. Proc Natl Acad Sci U S A. 1985 May;82(9):2844–2846. doi: 10.1073/pnas.82.9.2844. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Byrne B. C., Brussard T. B., Bruns P. J. Induced resistance to 6-methylpurine and cycloheximide in tetrahymena. I. Germ line mutants of T. thermophila. Genetics. 1978 Aug;89(4):695–702. doi: 10.1093/genetics/89.4.695. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Challoner P. B., Amin A. A., Pearlman R. E., Blackburn E. H. Conserved arrangements of repeated DNA sequences in nontranscribed spacers of ciliate ribosomal RNA genes: evidence for molecular coevolution. Nucleic Acids Res. 1985 Apr 11;13(7):2661–2680. doi: 10.1093/nar/13.7.2661. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Larson D. D., Blackburn E. H., Yaeger P. C., Orias E. Control of rDNA replication in Tetrahymena involves a cis-acting upstream repeat of a promoter element. Cell. 1986 Oct 24;47(2):229–240. doi: 10.1016/0092-8674(86)90445-9. [DOI] [PubMed] [Google Scholar]
  5. Mayo K. A., Orias E. Further evidence for lack of gene expression in the Tetrahymena micronucleus. Genetics. 1981 Aug;98(4):747–762. doi: 10.1093/genetics/98.4.747. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Nilsson J. R., Leick V. Nucleolar organization and ribosome formation in Tetrahymena pyriformis GL. Exp Cell Res. 1970 Jun;60(3):361–372. doi: 10.1016/0014-4827(70)90529-x. [DOI] [PubMed] [Google Scholar]
  7. Orias E. Alternative interpretation of the molecular structure and somatic genetics of acid phosphatase-1 in Tetrahymena pyriformis. Biochem Genet. 1973 May;9(1):87–90. doi: 10.1007/BF00485593. [DOI] [PubMed] [Google Scholar]
  8. Orias E., Bruns P. J. Induction and isolation of mutants in Tetrahymena. Methods Cell Biol. 1976;13:247–282. [PubMed] [Google Scholar]
  9. Orias E., Hamilton E. P. Cytogamy: An Inducible, Alternate Pathway of Conjugation in TETRAHYMENA THERMOPHILA. Genetics. 1979 Apr;91(4):657–671. doi: 10.1093/genetics/91.4.657. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Pan W. C., Blackburn E. H. Single extrachromosomal ribosomal RNA gene copies are synthesized during amplification of the rDNA in Tetrahymena. Cell. 1981 Feb;23(2):459–466. doi: 10.1016/0092-8674(81)90141-0. [DOI] [PubMed] [Google Scholar]
  11. Pan W. C., Orias E., Flacks M., Blackburn E. H. Allele-specific, selective amplification of a ribosomal RNA gene in Tetrahymena thermophila. Cell. 1982 Mar;28(3):595–604. doi: 10.1016/0092-8674(82)90214-8. [DOI] [PubMed] [Google Scholar]
  12. Roberts C. T., Jr, Orias E. A cycloheximide-resistant mutant of Tetrahymena pyriformis. Exp Cell Res. 1973 Oct;81(2):312–316. doi: 10.1016/0014-4827(73)90520-x. [DOI] [PubMed] [Google Scholar]
  13. Spangler E. A., Blackburn E. H. The nucleotide sequence of the 17S ribosomal RNA gene of Tetrahymena thermophila and the identification of point mutations resulting in resistance to the antibiotics paromomycin and hygromycin. J Biol Chem. 1985 May 25;260(10):6334–6340. [PubMed] [Google Scholar]
  14. Yao M. C., Gall J. G. A single integrated gene for ribosomal RNA in a eucaryote, Tetrahymena pyriformis. Cell. 1977 Sep;12(1):121–132. doi: 10.1016/0092-8674(77)90190-8. [DOI] [PubMed] [Google Scholar]
  15. Yu G. L., Hasson M., Blackburn E. H. Circular ribosomal DNA plasmids transform Tetrahymena thermophila by homologous recombination with endogenous macronuclear ribosomal DNA. Proc Natl Acad Sci U S A. 1988 Jul;85(14):5151–5155. doi: 10.1073/pnas.85.14.5151. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from Proceedings of the National Academy of Sciences of the United States of America are provided here courtesy of National Academy of Sciences

RESOURCES