Partial deletions of the W chromosome due to reciprocal translocation in the silkworm Bombyx mori

H. Abe*, M. Seki, F. Ohbayashi, N. Tanaka, J. Yamashita, T. Fujii, T. Yokoyama, Masateru Takahashi, Y. Banno, K. Sahara, A. Yoshido, J. Ihara, Y. Yasukochi, K. Mita, M. Ajimural, M. G. Suzuki, T. Oshiki, T. Shimada

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

In the silkworm, Bombyx mori (female, ZW; male, ZZ), femaleness is determined by the presence of a single W chromosome, irrespective of the number of autosomes or Z chromosomes.The W chromosome is devoid of functional genes, except the putative female-determining gene (Fem). However, there are strains in which chromosomal fragments containing autosomal markers have been translocated on to W. In this study, we analysed the W chromosomal regions of the Zebra-W strain (T(W;3)Ze chromosome) and the Black-egg-W strain (T(W;10)+ w-2 chromosome) at the molecular level. Initially, we undertook a project to identify W-specific RAPD markers, in addition to the three already established W-specific RAPD markers (W-Kabuki, W-Samurai and W-Kamikaze). Following the screening of 3648 arbitrary 10-mer primers, we obtained nine W-specific RAPD marker sequences (W-Bonsai, W-Mikan, W-Musashi, W-Rikishi, W-Sakura, W-Sasuke, W-Yukemuri-L, W-Yukemuri-S and BMC1-Kabuki), almost all of which contained the border regions of retrotransposons, namely portions of nested retrotransposons. We confirmed the presence of eleven out of twelve W-specific RAPD markers in the normal W chromosomes of twentyfive silkworm strains maintained in Japan.These results indicate that the W chromosomes of the strains in Japan are almost identical in type.The Zebra-W strain (T(W;3)Ze chromosome) lacked the W-Samurai and W-Mikan RAPD markers and the Black-egg-W strain (T(W;10)+ w-2 chromosome) lacked the W-Mikan RAPD marker.These results strongly indicate that the regions containing the W-Samurai and W-Mikan RAPD markers or the W-Mikan RAPD marker were deleted in the T(W;3)Ze and T(W;10)+ w-2 chromosomes, respectively, due to reciprocal translocation between the W chromosome and the autosome. This deletion apparently does not affect the expression of Fem; therefore, this deleted region of the W chromosome does not contain the putative Fem gene.

Original languageEnglish (US)
Pages (from-to)339-352
Number of pages14
JournalInsect Molecular Biology
Volume14
Issue number4
DOIs
StatePublished - Aug 1 2005

Keywords

  • Bombyx mori
  • RAPD
  • Reciprocal translocation
  • Retrotransposon
  • Sex chromosome
  • W chromosome

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Insect Science

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