title: Genomic sequence of a 320-kb segment of the Z chromosome of Bombyx mori containing a kettin ortholog.
abstract: The sex chromosome constitution of the silkworm, Bombyx mori, is ZW in the female and ZZ in the male. Very little molecular information is available about the Z chromosome in Lepidoptera, although the topic is interesting because of the absence of gene dosage compensation in this chromosome. We constructed a 320-kb BAC contig around the Bmkettin gene on the Z chromosome in Bombyx and determined its nucleotide sequence by the shotgun method. We found 13 novel protein-coding sequences in addition to Bmkettin. All the transposable elements detected in the region were truncated, and no LTR retrotransposons were found, in stark contrast to the situation on the W chromosome. In this 320-kb region, four genes for muscle proteins (Bmkettin, Bmtitin1, Bmtitin2, and Bmprojectin) are clustered, together with another gene (Bmmiple) on the Z chromosome in B. mori; their orthologs are also closely linked on chromosome 3 in Drosophila, suggesting a partial synteny. Real-time RT-PCR experiments demonstrated that transcripts of 13 genes of the 14 Z-linked genes found accumulated in larger amounts in males than in female moths, indicating the absence of gene dosage compensation. The implications of these findings for the evolution and function of the Z chromosome in Lepidoptera are discussed.
authors.affiliation: Department of Agricultural and Environmental Biology, University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, 113-8657 Tokyo, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Koike
authors.forename: K
authors.initials: K
authors.lastname: Mita
authors.forename: M G
authors.initials: MG
authors.lastname: Suzuki
authors.forename: S
authors.initials: S
authors.lastname: Maeda
authors.forename: H
authors.initials: H
authors.lastname: Abe
authors.forename: K
authors.initials: K
authors.lastname: Osoegawa
authors.forename: P J
authors.initials: PJ
authors.lastname: deJong
authors.forename: T
authors.initials: T
authors.lastname: Shimada
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D012831:Bombyx / Q000235:genetics*; D002874:Chromosome Mapping; D016386:Chromosome Walking; D022202:Chromosomes, Artificial, Bacterial / Q000235:genetics; D064211:Connectin; D020451:Contig Mapping; D029721:Drosophila Proteins; D020224:Expressed Sequence Tags; D005260:Female; D015723:Gene Library; D017344:Genes, Insect; D019476:Insect Proteins / Q000235:genetics*; D008297:Male; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000235:genetics*; D017422:Sequence Analysis, DNA; D012727:Sex Characteristics; D012730:Sex Chromosomes / Q000235:genetics*
chemical_list: D064211:Connectin; D029721:Drosophila Proteins; D019476:Insect Proteins; D009124:Muscle Proteins; C577347:sls protein, Drosophila