, Volume 114, Issue 6, pp 410–419 | Cite as

NOR activity and repeat sequences of the paternal sex ratio chromosome of the parasitoid wasp Trichogramma kaykai

  • Joke J. F. A. van Vugt
  • Silvester de Nooijer
  • Richard Stouthamer
  • Hans de Jong
Research Article


Part of the male population of the wasp Trichogramma kaykai carries a B chromosome that manipulates its host sex ratio in favour of males. The only known repeat on this paternal sex ratio (PSR) chromosome is the 45S rDNA, which includes here five different internal transcribed spacer 2 (ITS2) sequences. In this report, we describe that only part of these ITS2 sequences is transcribed. The absence of transcription of some ITS2 sequences might explain the presence of multiple ITS2 sequences on the PSR chromosome since homogenization of rDNA spacers is thought to occur only in transcribed regions. Analysis of the only other known tandem repeat in Trichogramma, the EcoRI repeat, showed that it is absent from the PSR chromosome, and that the T. kaykai EcoRI repeat has 98 and 77% DNA sequence homology with the T. deion and T. brassicae EcoRI repeats, respectively. The size of the PSR chromosome measures 9 Mbp and is equal to 3.9% of the haploid T. kaykai genome. Finally, fluorescent in situ hybridization with a pool of high and moderate repetitive T. kaykai DNA (C0t-50) revealed only a very few major tandem repeats on the Trichogramma genome and only 45S rDNA on the PSR chromosome.


Genome Size Isofemale Line Trichogramma Species Large Tandem Repeat Deoxythymidine Triphosphate 
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We thank Dr. J. S. Johnston from Texas A&M University, USA, and Mr. Patrick Verbaarschot for their help on estimating the genome size. We also thank Mrs. Jannie Wennekes for her help on the FISH of the EcoRI repeat and Ms. Penka Pavlova for measuring the fluorescence intensity of metaphase chromosomes. We also acknowledge the Dutch Science Foundation (NWO-ALW 810.34.006) for their financial support.


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Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  • Joke J. F. A. van Vugt
    • 1
    • 4
  • Silvester de Nooijer
    • 2
  • Richard Stouthamer
    • 3
  • Hans de Jong
    • 2
  1. 1.Laboratory of EntomologyWageningen UniversityWageningenThe Netherlands
  2. 2.Laboratory of GeneticsWageningen UniversityWageningenThe Netherlands
  3. 3.Department of EntomologyUniversity of CaliforniaRiversideUSA
  4. 4.Department of Molecular Biology, NCMLSRadboud UniversityNijmegenThe Netherlands

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