Biopolym. Cell. 2019; 35(3):229-230.
Chronicle and Information
The dispersal of ribosomal gene sequences in the karyotype of Coturnix japonica
1, 2Saifitdinova A., 3Galkina S., 3Kulak M., 4Fillon V., 3Volodkina V., 2, 5Pavlova O., 3Gaginskaya E.
  1. Herzen State Pedagogical University of Russia
    Saint Petersburg, Russia
  2. International Centre of Reproductive Medicine
    Saint Petersburg, Russia
  3. Saint Petersburg State University
    Saint Petersburg, Russia
  4. National Institute of Agricultural Research
    Toulouse, France
  5. Beagle Ltd.
    Saint Petersburg, Russia


Numerous copies of rDNA genes form nucleolar organizer regions (NORs) on chromosome and give rise to the interphase nucleoli. Bird species commonly have a single pair of the NOR bearing chromosomes in the karyotype (Schmid et al., 1982). Japanese quail is an exception and has three pairs of chromosomes with active NOR (McPherson et al., 2014). Even within a single NOR array individual sequences may differ (Kim et al., 2018). This work was aimed at studying the individual sequences that make up different NORs in Coturnix japonica. Methods: Using primers to the conserved region of the 18S ribosomal RNA gene, we amplified rDNA the range of fragments from the quail genome karyotype. The rDNA fragments were cloned, sequenced, analyzed bioinformatically and mapped by FISH. Results: Ribosomal gene derivatives were found to localize on the short heterochromatic arms of all acrocentric chromosomes in the complement. In addition to functional NOR sequences, we have found chimeric sequences containing fragments of transposable elements, fragments of MHC genes and some others. As it was shown earlier active transcription makes NOR a target for transposons and causes mutual amplification of the chimeric sequences of transposons and ribosomal genes (Buzdin et al., 2007). Conclusions: In the genome of Japanese quail transposition of NOR sequences apparently led to the dispersal and amplification of NORs, three of which retained their functionality. Funding: Financial and technical support: RFBR #18-04-01276-a, Research Resource Centres “Chromas” and “Molecular and Cell Technologies”. References: Schmid M, Loser C, Schmidtke J, Engel W. Evolutionary conservation of a common pattern of activity of nucleolus organizers during spermatogenesis in vertebrates. Chromosoma, 1982. 86:149–179. McPherson MC, Robinson CM, Gehlen LP, Delany ME. Comparative cytogenomics of poultry: mapping of single gene and repeat loci in the Japanese quail (Coturnix japonica). Chromosome Res. 2014. 22:71-83. Kim JH, Dilthey AT, Nagaraja R, Lee HS, Koren S, Dudekula D, Wood III WH, Piao Y, Ogurtsov AY, Utani K, Noskov VN, Shabalina SA, Schlessinger D, Phillippy AM, Larionov V. Variation in human chromosome 21 ribosomal RNA genes characterized by TAR cloning and long-read sequencing. NAR, 2018. 46:6712-6725. Buzdin A, Gogvadze E, Lebrun M-H. Chimeric retrogenes suggest a role for the nucleolus in LINE amplification. FEBS Letters, 2007. 581:2877-2882.