Controls somatic sexual differentiation. Binds directly and specifically to the FBE (fat body enhancer) of the yolk protein 1 and 2 genes (Yp1 and Yp2). This enhancer is sufficient to direct the female-specific transcription characteristic of the Yp genes in adult fat bodies. Involved in regulation of male-specific expression of takeout in brain-associated fat body.

(UniProt, P23023)

The dsx gene regulates sexual differentiation of somatic tissues. Null alleles convert chromosomally male and female flies into sterile intersexes of similar phenotype. Dominant alleles (e.g., dsxD, dsxM, dsxT) transform females into intersexes when heterozygous with a normal allele, and into phenotypic males when homozygous or heterozygous with a dsx-null allele or deficiency, but they have no effect in males. Most alleles at dsx affect both sexes; however, some alleles affect only one sex. The recessive allele dsx11 converts males into intersexes and is complemented by dominant dsx alleles and recessive alleles that affect only females (dsx22) (Baker and Ridge; Nothiger et al., 1987). Double-mutant combinations of dsx null mutations with loss-of-function alleles at tra, tra2, and ix result in a doublesex phenotype (Mukherjee and Hildreth, 1971, Genetica 42: 338-52; Baker and Ridge; Nothiger et al., 1987). Double-mutant combinations of dsxD/+ with null alleles of tra and tra2 convert females into phenotypic males or with ix into more male-like intersexes (Baker and Ridge; Nothiger et al., 1987). The dose of dsx alleles can alter the phenotype; triploid female flies dsxD/+/+ are sterile and with a weak external dsx phenotype (Gowen and Fung, 1957; Nothiger et al., 1987); diploid female flies that are dsxD/+, but also carry a dsx+ duplication Tp(3;Y)P92 are sterile but female in appearance (Nothiger et al., 1987). Germline sexual differentiation is not dependent on dsx+ function; only the chromosomal constitution determines the sex of transplanted dsxM/+, dsx1, dsxD/+, and dsxD/dsx1 germ cells (Nothiger, Roost, and Schupbach, 1980, DIS 55: 118; Schupbach, 1982, Dev. Biol. 89: 117-27). The dsx+ gene does not appear to encode any vital functions (Baker and Ridge). The normal body size differences between male and female flies is maintained in dsx-null mutants (Hildreth) and in females heterozygous for dsxD/+, dsxD/dsx1 (Fung and Gowen, 1957; Baker and Ridge) and dsxM/+ (Nothiger et al., 1987). The sexcomb bristles on the prothoracic basitarsus in both sexes of dsx-null homozygotes (Hildreth; Mukherjee, and Hildreth; Baker and Ridge) and female dsxD/dsx1 (Nothiger et al., 1987) are intermediate in number, morphology, and position compared with the sexcomb bristles in normal males and the transverse row bristles in normal females. The central sexcomb bristle is retained in dsx-null mutants (Hildreth). In dsx-null mutants, the pigmentation of the fifth tergite is intermediate between the completely pigmented male and the posteriorly pigmented female tergite, whereas the sixth tergite is darkly pigmented (Hildreth; Baker, and Ridge). Female flies that are dsxD/+ or dsxM/+ are similar to dsx homozygotes (Fung and Gowen, 1957; Duncan and Kaufman, 1975, Genetics 80: 733-52; Baker and Ridge; Nothiger et al., 1987). Male dsx flies have a seventh tergite and sternite with bristles (Hildreth; Baker, and Ridge). Female flies heterozygous for dominant alleles and either dsx1 or dsx deficiencies have the male number of tergites and sternites with the male pattern of pigmentation (Duncan and Kaufman, 1975; Baker and Ridge; Nothiger et al., 1980; Nothiger et al., 1987). By clonal analysis, the action of dsx has been shown to be cell autonomous in the differentiation of the sexcombs and pigmentation of the abdominal tergites; dsx+ is required until the end of the larval period for the proper sexual differentiation of the sexcombs and into the pupal period, close to the time of the termination of divisions of the abdominal histoblasts, for proper sexual differentiation of the abdominal histoblasts and for proper sexual differentiation of the abdomen (Baker and Ridge). Both male and female genitalia are formed in dsx null mutant flies and in female flies heterozygous for dominant alleles (Fung and Gowen, 1957; Hildreth, 1965; Epper, 1981, Dev. Biol. 88: 104-14; Nothiger et al., 1987); a second penis differentiates with a reduced aedeagus and parameres within the female vaginal area (Hildreth). In dsxD/+ females, the development of the female genitalia and second penis are very similar to that of dsx-null flies, whereas in dsxM/+ females the female genitalia are more severely reduced (Gowen and Fung, 1975; Baker and Ridge; Nothiger et al., 1980; Epper, 1981; Nothiger et al., 1987). Male genitalia from dsx null flies and females heterozygous for dsx dominant alleles contain all elements except a basal apodeme but other external structures such as the penis and accessory elements are reduced and not as well formed (Fung and Gowen, 1957; Hildreth; Epper, 1981). The internal duct systems develop but can vary between dual female and male ducts and a single poorly differentiated duct (Hildreth); a similar range of phenotypes for the internal ducts is found in dsxD/+ (Fung and Gowen, 1957) and dsxM/+ (Nothiger et al., 1980). Based on fate mapping and analysis of the morphogenesis of the dsxD/+ genital disc, the female genitalia and second penis are generated from the female genital primordium, and the male genitalia from the male genital primordium and the production of both types of genitalia in dsx flies results from derepression of both genital primordia (Epper, 1981; Epper, 1983, Wilhelm Roux's Arch. Dev. Biol. 192: 280-84). The intersexual analia differentiate as lateral plates, which are smaller than normal male lateral anal plates and do not have the ventral anal plate found in females (Hildreth; Baker, and Ridge; Epper, 1981). The bristle pattern is rather male-like but with one clearly identifiable long dorsal bristle that is female (Epper, 1981). The gonads are often rudimentary, but occasionally female dsx-null as well as dsxD/+ flies have well developed ovaries and eggs (Hildreth, Fung, and Gowen, 1957; Schupbach, 1982; Bownes, Dempster, and Blair, 1983, J. Embryol. Exp. Morph. 75: 241-57) whereas in male dsx-null flies, the gonads are poorly developed and no sperm are formed (Hildreth; Schupbach, 1982). Female and male dsx flies and female dsxD/+ flies make yolk protein but in amounts less than for normal females (Postelthwait, Bownes, and Jowett, 1980, Dev. Biol. 79: 379-87; Ota, Fukunaga, Kawabe, and Oishi, 1981, Genetics 99: 429-41). In dsxD/+ females less yolk protein synthesis occurs compared to normal females; little or no yolk protein mRNA is made in the rudimentary gonads, but measurements from adult flies show that from an initially low level yolk protein transcripts increase to nearly wildtype levels but without efficient conversion into protein (Bownes, Dempster, and Blair, 1983). The male-specific transcripts 316, 355a, and 355b, made by the male accessory gland, are also produced in male flies rendered intersexual by the mutation dsx11, which does not affect female flies; in addition, females that are dsxD/+ or dsxM/+ express the male-specific transcripts, although at reduced levels (Chapman and Wolfner, 1988, Dev. Biol. 126: 195-202). Females homozygous for dsx do not exhibit male courtship behaviors (McRobert and Tompkins, 1985, Genetics 111: 89-96; B. Taylor, unpublished). These dsx females do not make 7, 11 dienes, and 7 monoenes compared to normal females (Jallon, 1984, Behav. Genet. 14: 441-78); they elicit less courtship than dsx+ females from control males (McRobert and Tompkins, 1985). Female flies that are dsxD/+ or dsxM/+ also fail to express male courtship behaviors (Duncan and Kaufman, 1975; B. Taylor, unpublished). Males homozygous for dsx court but show reduced levels of courtship directed toward females and young males and greater-than-normal levels of courtship directed at mature males (McRobert and Tompkins, 1985). Mature dsx males make some pheromonal substances (Jallon, 1984) and elicit more courtship than dsx+ males from control males (McRobert and Tompkins, 1985). Female flies homozygous for dsx-null alleles or mutant for dsx dominant alleles do not make the male-specific abdominal muscle unlike their male siblings (B. Taylor, unpublished).