Novel female-specific trans-spliced and alternative splice forms of dsx in the silkworm Bombyx mori

Abstract

The Bombyx mori doublesex gene (Bmdsx) plays an important role in somatic sexual development. Its pre-mRNA splices in a sex-specific manner to generate two female-specific and one male-specific splice forms. The present study investigated six novel dsx variants generated by trans-splicing between female dsx transcripts and two additional novel genes, dsr1 and dsr2. Expression analysis indicated that Bmdsx-dsr1 represented splicing noise, whereas dsr2, which trans-spliced with dsx to generate five variants, regulated the expression of the female-specific B. mori dsx transcript BmdsxFs. We unexpectedly found a novel exon 2n insertion during Bmdsx transcription, which did not influence the validity of the novel protein, BmDSXF3. Ectopic expression of BmDSXF3 repressed the pheromone-binding protein gene and the testis-specific gene A2 in males, and activated of the storage protein 1 gene. Our findings suggest that trans-splicing is a novel regulatory function of Bmdsx, which participates in female sexual development by regulating the expression of three BmDSXF proteins.