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

Abstract

The Bombyx mori doublesex (Bmdsx), a homologue of doublesex of Drosophila, is the bottom most gene of the sex determination cascade. Bmdsx plays a very crucial role in somatic sexual development. Its pre-mRNA sex-specifically splices to generate two splice variants; one encodes female-specific and the other encodes male-specific polypeptides which differ only at their C-termini. The open reading frame of Bmdsx consists of 5 exons, of which exons 3 and 4 are female-specific and are skipped in males. In the present study, we have identified a third splice form of the Bmdsx which is specific only to females and differs from the previously reported Bmdsxf isoform by the presence of 15 bp sequence. This new female splice form is generated as a result of alternative 5' splice site selection in the third exon adding additional 15 bp sequence in exon 3 which results in alteration of the reading frame leading to incorporation of an early stop codon. Thus the protein encoded by this splice form is 20 aa shorter than the known BmDsxF. Initial results obtained from the study of dsx homologues in Saturniid silkmoths suggest that both the female-specific Dsx proteins are essential for female sexual differentiation. It remains to be seen whether female-specific multiple splice forms of dsx are characteristic feature of only silkmoths or widespread among lepidopterans. The findings that sex determination mechanism is unique in lepidopterans offer an opportunity to develop genetic sexing methods in beneficial as well as economically destructive lepidopteran pests.

Transgene-based, female-specific lethality system for genetic sexing of the silkworm, Bombyx mori

“…Two relevant splice variants are indicated. Additional splice variants are known for both Bmdsx and Pgdsx (13,35,36). E, exons; I, introns.…”

New Insights into the Genomic Organization and Splicing of the Doublesex Gene, a Terminal Regulator of Sexual Differentiation in the Silkworm Bombyx mori

“…Earlier studies reported that Bmdsx transcripts are spliced in a sex-specific manner to yield two female forms ( Bmdsx F1 and Bmdsx F2 ) and one male form ( Bmdsx M ) [19,30]. In a recent study, we predicted the existence of a novel exon, 2n, and a third female-specific splice form Bmdsx F3 [31].…”

“…This is the case in M. domestica and A. mellifera in which in addition to sex-specific transcripts there is a dsx transcript encoding a common Dsx protein in males and females [26,27]. In Aedes aegypti , A. assama , A. mylitta and B. mori a second female-specific Dsx protein is predicted [28-30]. Recently, we proposed that B. mori has a third female-specific Dsx protein predicted to arise from a novel trans-spliced transcript, Bmdsx-dsr2 d [31].…”

Lepidopteran Sex Determination: A Cascade of Surprises

“…A dsx homolog (Bmdsx) in B. mori is present on chromosome 25, and its pre-mRNA is spliced in a sex-specific manner producing 2 female-and 1 male-specific isoforms Shukla et al, 2011]. Bmdsx harbors 5 exons and 4 introns out of which exons 1, 2, and 5 are constitutively spliced, whereas exons 3 and 4 are female-specific .…”

“…Bmdsx harbors 5 exons and 4 introns out of which exons 1, 2, and 5 are constitutively spliced, whereas exons 3 and 4 are female-specific . Both female-specific isoforms of Bmdsx differ from each other by a 15-bp alternatively spliced (alternative 5 ′ splice site selection) sequence present after exon 3 [Shukla et al, 2011]. Due to this difference, both BmDSX F proteins differ from each other by 18 amino acids.…”