Analysis of the biological functions of a doublesex homologue in Bombyx mori

Abstract

We have previously reported that Bmdsx, a homologue of the sex-determining gene doublesex ( dsx), was sex-specifically expressed in various tissues of the silkworm. The primary transcript of Bmdsx is alternatively spliced in males and females to yield sex-specific mRNAs that encode male-specific (BmDSXM) and female-specific (BmDSXF) polypeptides. In the studies reported here, we expressed BmDSXF in males from a ubiquitous promoter and examined its regulatory activities. We show that BmDSXF functions as a positive regulator of the hexameric storage protein termed SP1 and vitellogenin genes that are predominantly expressed in females. We also show that expression of Bmdsx(F) in males results in the repression of the pheromone-binding protein gene that is preferentially expressed in males. Gel-mobility shift assays demonstrated that BmDSX proteins bind to the sequence (ACATTGT) between -95 and -89 nt relative to the transcriptional initiation site of the vitellogenin gene. These results strongly suggest that Bmdsx is a final regulatory gene in the hierarchy of regulatory genes controlling the expression of female-specific protein in Bombyx mori.

Sex Determination in Insects: Variations on a Common Theme

“…In addition, recent studies suggest that changes in temporal and spatial expression of dsx by gene regulatory networks providing positional information may contribute to this diversity [Rideout et al, 2010;Robinett et al, 2010]. A prominent role of dsx in properly implementing the selected sexual developmental program has not only been validated in D. melanogaster [Baker and Wolfner, 1988], but also in other dipterans, M. domestica [Hediger et al, 2004] and C. capitata [Saccone et al, 2008], in the lepidopteran B. mori [Suzuki et al, 2003[Suzuki et al, , 2005 as well as in the coleopterans T. castaneum [Shukla and Palli, 2012a] and horned beetles [Kijimoto et al, 2012]. Hence, dsx is thought to play a widely conserved role in integrating information about sexual identity in the general developmental program [Vincent et al, 2001].…”

Identification of a Male-Specific RNA Binding Protein That Regulates Sex-Specific Splicing of Bmdsx by Increasing RNA Binding Activity of BmPSI

“…Like dsx, the primary transcript of the Bmdsx gene is alternatively spliced in males and females to yield sex-specific mRNAs that encode male-specific (BmDSXM) and female-specific (BmDSXF) polypeptides (34,42). Transgenic analysis of Bmdsx revealed that Bmdsx functions as a double-switch gene at the bottom of the sex determination cascade of B. mori (43,44). Despite these similarities between dipteran dsx orthologues and Bmdsx, the underlying mechanisms for sex-specific splicing are clearly different.…”

Establishment of a Novel In Vivo Sex-Specific Splicing Assay System To Identify a trans-Acting Factor That Negatively Regulates Splicing of Bombyx mori dsx Female Exons

“…Like dsx, the primary transcript of the Bmdsx gene is alternatively spliced in males and females to yield sex-specific mRNAs that encode male-specific (BmDSXM) and femalespecific (BmDSXF) polypeptides (36,42). Transgenic analysis of Bmdsx revealed that Bmdsx functions as a double-switch gene at the final step in the B. mori sex determination cascade (43,44). Despite these similarities between dsx and Bmdsx, the underlying mechanism for sex-specific splicing is clearly different.…”