Formation of the male-specific muscle in female Drosophila by ectopic fruitless expression

A genetically defined element of the fruitless (fru) locus in Drosophila melanogaster regulates the development of a male-specific muscle spanning the fifth abdominal segment in adult males, the ‘muscle of Lawrence’ (MOL). The region is defined by two cytological deletions, each with a breakpoint that co-maps with previously described mutant courtship phenotypes at cytogenetic interval 91B on the third chromosome. Flies that carry both of these deletions are viable, and males express abnormalities of courtship similar to those caused by the fru inversion breakpoint at 91B. In addition, these double-deletion males show the complete absence of the MOL, suggesting that they have little or no gene expression of a postulated MOL determinant; the musculature in the fifth abdominal segment of these mutants to indistinguishable from that of a normal female. Other mutant combinations that produce fruitless courtship phenotypes—including deletion and inversion breakpoints, and a marked transposon inserted at 91B—produce intermediate forms of the MOL. A new genetic variant, induced by imprecise excision of the marked transposon, is homozygous lethal and disrupts fru functions related to courtship and the MOL. The MOL is shown to be dispensable for fertility and is therefore not the causative factor of fru-induced behavioral sterility. These genetic variants and their phenotypic results are discussed with regard to a model for the organization of the fru locus.

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Differentiation of a male-specific muscle in Drosophila melanogaster does not require the sex-determining genes doublesex or intersex.

Genetics ◽

10.1093/genetics/132.1.179 ◽

1992 ◽

Vol 132 (1) ◽

pp. 179-191

Author(s):

B J Taylor

Keyword(s):

Drosophila Melanogaster ◽

Abdominal Segment ◽

Specific Form ◽

Null Alleles ◽

Abdominal Muscles ◽

Sexually Dimorphic ◽

Wild Type ◽

Specific Muscle ◽

Sex Lethal ◽

Male Specific

Abstract A pair of muscles span the fifth abdominal segment of male but not female Drosophila melanogaster adults. To establish whether genes involved in the development of other sexually dimorphic tissues controlled the differentiation of sex-specific muscles, flies mutant for five known sex-determining genes were examined for the occurrence of male-specific abdominal muscles. Female flies mutant for alleles of Sex-lethal, defective in sex determination, or null alleles of transformer or transformer-2 are converted into phenotypic males that formed male-specific abdominal muscles. Both male and female flies, when mutant for null alleles of doublesex, develop as nearly identical intersexes in other somatic characteristics. Male doublesex flies produced the male-specific muscles, whereas female doublesex flies lacked them. Female flies, even when they inappropriately expressed the male-specific form of doublesex mRNA, failed to produce the male-specific muscles. Therefore, the wild-type products of the genes Sex-lethal, transformer and transformer-2 act to prevent the differentiation of male-specific muscles in female flies. However, there is no role for the genes doublesex or intersex in either the generation of the male-specific muscles in males or their suppression in females.

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Innervation is essential for the development and differentiation of a sex-specific adult muscle in Drosophila melanogaster

Development ◽

10.1242/dev.121.8.2549 ◽

1995 ◽

Vol 121 (8) ◽

pp. 2549-2557 ◽

Cited By ~ 4

Author(s):

D.A. Currie ◽

M. Bate

Keyword(s):

Abdominal Segment ◽

De Novo ◽

Close Association ◽

Muscle Growth ◽

Abdominal Muscles ◽

Full Complement ◽

Development And Differentiation ◽

Specific Muscle ◽

Male Specific

The adult abdominal muscles in Drosophila are generated de novo during metamorphosis and form a simple and characteristic pattern. Throughout adult abdominal development there is a close association between nerves and myoblasts. However, the role of innervation in adult myogenesis is unclear. In males there is an additional muscle, which is unique to abdominal segment 5 (A5). This male specific muscle forms from the same pool of myoblasts as other dorsal muscles in A5 but develops several distinctive characteristics. Previous work indicates the genotype of the innervation of this male specific muscle may play a crucial role in its proper development, although the part played by innervation in the development of other muscles is unknown. Here we test directly the function of innervation in adult myogenesis in general and for the development and differentiation of the male specific muscle in particular. After denervation at the onset of metamorphosis, muscle growth is impaired although the overall muscle pattern continues to develop. Uniquely, the male specific muscle fails to form. Our results indicate that there is an essential role for innervation during the period of metamorphosis for the formation of a full complement of abdominal muscles and for muscle growth. Furthermore, innervation is absolutely required for the formation of the male specific muscle and the development of its special characteristics.

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