Genetic mapping of Z chromosome and identification of W chromosome-specific markers in the silkworm, Bombyx mori.

Laboratory of Molecular Genetics, Centre for DNA Fingerprinting and Diagnostics, ECIL Road, Nacharam, Hyderabad 500076, India.

In the silkworm, Bombyx mori, the female is the heterogametic (ZW) sex and the male is homogametic (ZZ). The female heterogamety is a typical situation in the insect order Lepidoptera. Although the W chromosome in silkworm is strongly female determining, no W-linked gene for a morphological character has been found on it. The Z chromosome carries important traits of economic value as well as genes for various phenotypic traits, but only 2% of molecular information based on its relative size is known. Studies conducted so far indicate that the Z-linked genes are not dosage compensated. In the present study, we constructed a genetic map of randomly amplified polymorphic DNA fragments (RAPD), simple sequence repeats (SSR), and fluorescent intersimple sequence repeat PCR (FISSR) markers for the Z chromosome using a backcross mapping population. A total of 16 Z-linked markers were identified, characterized, and mapped using od, a recessive trait for translucent skin as an anchor marker yielding a total recombination map of 334.5 cM. The linkage distances obtained suggested that the markers were distributed throughout the Z chromosome. Four RAPD and four SSR markers that were linked to W chromosome were also identified. The proposed mapping approach should be useful to identify and map sex-linked traits in the silkworm. The economic and evolutionary significance of Z- and W-linked genes in silkworm, in particular, and lepidopterans, in general, is discussed.

PMID: 15931240 [PubMed - indexed for MEDLINE]