scute (sis-b) function in Drosophila sex determination.

摘要: The primary sex determination signal, the X chromosome-to-autosome (X/A) ratio, controls choice of sexual identity in Drosophila melanogaster embryo by regulating activity early promoter Sex-lethal gene, Sxl-Pe. This is activated females (2X/2A), while it remains off males (1X/2A). Promoter activation dependent upon X-linked numerator genes. One these genes, sisterless-b (sis-b), corresponds to scute (sc) locus achaete-scute complex, and encodes a helix-loop-helix transcription factor. In studies reported here we have used monoclonal antibodies study expression functioning sc(sis-b) protein. Sc first detected at nuclear cycle 6 7, well before Sxl-Pe active. At this stage, protein cytoplasm, not nucleus. Only after formation syncytial blastoderm, 10 11, does substantial fraction enter nucleus, import closely coincides with initial Consistent idea that dose critical for its function as an X-chromosome counting element, wild-type blastoderm embryos could be grouped into two classes based on level Western blot (immunoblot) analysis demonstrates difference correlates directly state Sxl gene. Finally, provide direct evidence forms heteromeric complexes vivo maternally derived Daughterless. complex likely activation.