Abe H, Seki M, Ohbayashi F, Tanaka N, Yamashita J, Fujii T, Yokoyama T, Takahashi M, Banno Y, Sahara K, Yoshido A, Ihara J, Yasukochi Y, Mita K, Ajimura M, Suzuki M G, Oshiki T, Shimada T
Department of Biological Production, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Japan.
Insect Mol Biol. 2005 Aug;14(4):339-52. doi: 10.1111/j.1365-2583.2005.00565.x.
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 twenty-five 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.
在家蚕（Bombyx mori，雌性，ZW；雄性，ZZ）中，雌性由单个W染色体的存在决定，而与常染色体或Z染色体的数量无关。W染色体除了假定的雌性决定基因（Fem）外，没有功能性基因。然而，存在一些品系，其中含有常染色体标记的染色体片段已易位到W染色体上。在本研究中，我们在分子水平上分析了斑马W品系（T（W；3）Ze染色体）和黑卵W品系（T（W；10）+（w - 2）染色体）的W染色体区域。最初，我们开展了一个项目，以鉴定除了三个已确立的W特异性随机扩增多态性DNA（RAPD）标记（W - 歌舞伎、W - 武士和W - 神风）之外的W特异性RAPD标记。在筛选了3648个任意的10聚体引物后，我们获得了九个W特异性RAPD标记序列（W - 盆景、W - 蜜柑、W - 武藏、W - 力士、W - 樱花、W - 佐助、W - 雪肌精 - L、W - 雪肌精 - S和BMC1 - 歌舞伎），几乎所有这些序列都包含反转录转座子的边界区域，即嵌套反转录转座子的部分。我们在保存在日本的25个家蚕品系的正常W染色体中确认了12个W特异性RAPD标记中的11个。这些结果表明，日本品系的W染色体在类型上几乎相同。斑马W品系（T（W；3）Ze染色体）缺乏W - 武士和W - 蜜柑RAPD标记，黑卵W品系（T（W；10）+（w - 2）染色体）缺乏W - 蜜柑RAPD标记。这些结果强烈表明，分别由于W染色体与常染色体之间的相互易位，T（W；3）Ze和T（W；10）+（w - 2）染色体中含有W - 武士和W - 蜜柑RAPD标记的区域或W - 蜜柑RAPD标记区域被删除。这种删除显然不影响Fem的表达；因此，W染色体的这个删除区域不包含假定的Fem基因。
