Identification of the female-determining region of the W chromosome in Bombyx mori

H. Abe, T. Fujii, N. Tanaka, T. Yokoyama, H. Kakehashi, M. Ajimura, K. Mita, Y. Banno, Y. Yasukochi, T. Oshiki, M. Nenoi, T. Ishikawa, T. Shimada

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Abstract

The W chromosome of the silkworm Bombyx mori is devoid of functional genes, except for the putative female-determining gene (Fem). To localize Fem, we investigated the presence of W-specific DNA markers on strains in which an autosomal fragment containing dominant marker genes was attached to the W chromosome. We produced new W-chromosomal fragments from the existing Zebra-W strain (T(W;3)Ze chromosome) by X-irradiation, and then carried out deletion mapping of these and sex-limited yellow cocoon strains (T(W;2)Y-Chu, -Abe and -Ban types) from different Japanese stock centers. Of 12 RAPD markers identified in the normal W chromosomes of most silkworm strains in Japan, the newly irradiated W(B-YL-YS)Ze chromosome contained three, the T(W;2)Y-Chu chromosome contained six, and the T(W;2)Y-Abe and -Ban chromosomes contained only one (W-Rikishi). To investigate the ability of the reduced W-chromosome translocation fragments to form heterochromatin bodies, which are found in nuclei of normal adult female sucking stomachs, we examined cells of the normal type p50 strain and the T(W;2)Y-Chu and -Abe strains. A single sex heterochromatin body was found in nuclei of p50 females, whereas we detected only small sex heterochromatin bodies in the T(W;2)Y-Chu strain and no sex heterochromatin body in the T(W;2)Y-Abe strain. Since adult females of all strains were normal and fertile, we conclude that only extremely limited region, containing the W-Rikishi RAPD sequence of the W chromosome, is required to determine femaleness. Based on a comparison of the normal W-chromosome and 7 translocation and W-deletion strains we present a map of Fem relative to the 12 W-specific RAPD markers.

Original languageEnglish
Pages (from-to)269-282
Number of pages14
JournalGenetica
Volume133
Issue number3
DOIs
Publication statusPublished - Jul 1 2008

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All Science Journal Classification (ASJC) codes

  • Animal Science and Zoology
  • Genetics
  • Plant Science
  • Insect Science

Cite this

Abe, H., Fujii, T., Tanaka, N., Yokoyama, T., Kakehashi, H., Ajimura, M., ... Shimada, T. (2008). Identification of the female-determining region of the W chromosome in Bombyx mori. Genetica, 133(3), 269-282. https://doi.org/10.1007/s10709-007-9210-1