Novel female-specific splice form of dsx in the silkworm, Bombyx mori |
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Authors: | Jayendra Nath Shukla Santosh Jadhav Javaregowda Nagaraju |
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Institution: | (1) Centre of Excellence for Genetics and Genomics of Silkmoths, Laboratory of Molecular Genetics, Centre for DNA Fingerprinting and Diagnostics, Tuljaguda, Nampally, Hyderabad, 500001, India; |
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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. |
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