TY - JOUR
T1 - Functional conservation and divergence of intersex, a gene required for female differentiation in Drosophila melanogaster
AU - Siegal, Mark L.
AU - Baker, Bruce S.
N1 - Funding Information:
Acknowledgements The authors thank Dixie-Ann Persaud, Hank Bayle, Thomas Kaufman, Robin Cooper, Douglas Harrison, and Liqun Luo and his laboratory members for reagents; members of the Baker lab for helpful advice; Cindy Smith for maintaining our mulberry tree; Peter Ray for donating mulberry leaves from his tree; Guennet Bohm for laboratory assistance; Dmitri Petrov and two anonymous reviewers for helpful comments; and Rachel Drysdale, Kathy Matthews and Bill Gelbart for guidance in naming transgenic constructs. This work was supported by NSF/Sloan Foundation and NIH NRSA postdoctoral fellowships awarded to M.L.S. and by an NIH grant to B.S.B.
Copyright:
Copyright 2008 Elsevier B.V., All rights reserved.
PY - 2005/1
Y1 - 2005/1
N2 - In Drosophila melanogaster, somatic sexual differentiation is regulated by a well characterized genetic hierarchy, by which the ratio of X chromosomes to autosomes (X:A) ultimately directs the deployment of sex-specific transcription factors encoded by doublesex (dsx) and fruitless (fru). In other dipterans, the X:A ratio is not the primary sex-determination signal. Correspondingly, the Drosophila hierarchy is not fully conserved. In all non-drosophilid fly species examined, Sex-lethal (Sxl), the master switch at the top of the Drosophila hierarchy, does not control somatic sex. This rapid divergence contrasts with the apparently deep conservation of dsx, which in Drosophila controls virtually all aspects of somatic sex except for male courtship behavior (which is controlled by fru). Sex-specific dsx mRNAs have been reported in Diptera, Lepidoptera and Hymenoptera, and dsx homologs in nematodes and mammals are required for aspects of male differentiation. Thus, it seems that the bottom of the hierarchy is rather ancient, especially compared with the top. To test this, we cloned insect and vertebrate homologs of the Drosophila gene intersex (ix), which functions together with dsx at the bottom of the hierarchy in females. When expressed in D. melanogaster females mutant at the endogenous ix gene, dipteran and lepidopteran ix homologs restore proper sexual differentiation, substantiating the hypothesis that ix, like dsx, is broadly conserved. When the mouse homolog is expressed it produces a dominant-negative phenotype suggesting partial functional divergence. Our results raise the possibility that a functional association between ix - and dsx-related gene products existed before the origin of the bifunctional dsx gene used in insect sex determination.
AB - In Drosophila melanogaster, somatic sexual differentiation is regulated by a well characterized genetic hierarchy, by which the ratio of X chromosomes to autosomes (X:A) ultimately directs the deployment of sex-specific transcription factors encoded by doublesex (dsx) and fruitless (fru). In other dipterans, the X:A ratio is not the primary sex-determination signal. Correspondingly, the Drosophila hierarchy is not fully conserved. In all non-drosophilid fly species examined, Sex-lethal (Sxl), the master switch at the top of the Drosophila hierarchy, does not control somatic sex. This rapid divergence contrasts with the apparently deep conservation of dsx, which in Drosophila controls virtually all aspects of somatic sex except for male courtship behavior (which is controlled by fru). Sex-specific dsx mRNAs have been reported in Diptera, Lepidoptera and Hymenoptera, and dsx homologs in nematodes and mammals are required for aspects of male differentiation. Thus, it seems that the bottom of the hierarchy is rather ancient, especially compared with the top. To test this, we cloned insect and vertebrate homologs of the Drosophila gene intersex (ix), which functions together with dsx at the bottom of the hierarchy in females. When expressed in D. melanogaster females mutant at the endogenous ix gene, dipteran and lepidopteran ix homologs restore proper sexual differentiation, substantiating the hypothesis that ix, like dsx, is broadly conserved. When the mouse homolog is expressed it produces a dominant-negative phenotype suggesting partial functional divergence. Our results raise the possibility that a functional association between ix - and dsx-related gene products existed before the origin of the bifunctional dsx gene used in insect sex determination.
KW - Drosophila
KW - Evolution
KW - Intersex protein
KW - Sex determination (genetics)
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U2 - 10.1007/s00427-004-0445-x
DO - 10.1007/s00427-004-0445-x
M3 - Article
C2 - 15645316
AN - SCOPUS:12144283012
SN - 0949-944X
VL - 215
SP - 1
EP - 12
JO - Development Genes and Evolution
JF - Development Genes and Evolution
IS - 1
ER -