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

Abstract

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 Zlinked 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. Heredity (2005) 95, 148-157.

Novel female-specific splice form of dsx in the silkworm, Bombyx mori

“…A silkworm stock Pure Mysore (sex-limited), where male and female larvae could be distinguished by virtue of sexlimited larval markings (Nagaraja et al 2005), was used as the source of RNA. The female larvae possess markings in the cephalic and thoracic segments while the male larvae lack the same and thus sex separation is made possible from early IV instar stage (Fig.…”

A rearrangement of the Z chromosome topology influences the sex-linked gene display in the European corn borer, Ostrinia nubilalis

“…Phenotypic traits controlled by loci on the Z chromosome in the domesticated silkworm, Bombyx mori, include cuticle density (loci os, sex-linked translucent, and od, distinct translucent), body shape (e, elongated), molting (nm-s, non-molting-s), larval maturity (lm, late maturity) and body color (sch, sexlinked chocolate) (Fujii et al 2008). Genetic linkage maps of the B. mori Z chromosome (Nagaraja et al 2005) have proven valuable in isolating the positions of sch ) and shaker (shkr), which are linked to economically important male silking traits (Zhu et al 2001), and behavioral traits, respectively (Duan et al 2010). Among other species of Lepidoptera, the Z chromosome encodes the period (per) gene that governs clock and circadian periodicity in the silkmoth, Antheraea pernyi (Gotter et al 1999), hybrid sterility factors in the Postman butterfly, Heliconius melpomene (Jiggins et al 2001a), and ecological traits such as diapause duration and male pheromone response in the European corn borer, Ostrinia nubilalis (Thomas et al 2003;Dopman et al 2005).…”

Construction of a Single Nucleotide Polymorphism Linkage Map for the Silkworm, Bombyx mori, Based on Bacterial Artificial Chromosome End Sequences

“…At present, several silkworm linkage maps based on molecular markers are available, including randomly amplified polymorphic DNA (RAPD) (Promboon et al 1995;Yasukochi 1998), simple sequence repeat and RAPDs (Nagaraja et al 2005), amplified fragment length polymorphisms (AFLP) (Tan et al 2001), restriction fragment length polymorphisms (Shi et al 1995;Kadono-Okuda et al 2002;Nguu et al 2005), and microsatellites (Prasad et al 2005;Miao et al 2005). Recently, karyotyping of the chromosomes using bacterial artificial chromosome (BAC)-FISH based on Yasukochi's RAPD map was also reported (Yoshido et al 2005).…”