Drosophila Hox and sex-determination genes control segment elimination through EGFR and extramacrochetae activity.
The formation or suppression of particular structures is a major change occurring in development and evolution. One example of such change is the absence of the seventh abdominal segment (A7) in Drosophila males. We show here that there is a down-regulation of EGFR activity and fewer histoblasts in the male A7 in early pupae. If this activity is elevated, cell number increases and a small segment develops in the adult. At later pupal stages, the remaining precursors of the A7 are extruded under the epithelium. This extrusion requires the up-regulation of the HLH protein Extramacrochetae and correlates with high levels of spaghetti-squash, the gene encoding the regulatory light chain of the non-muscle myosin II. The Hox gene Abdominal-B controls both the down-regulation of spitz, a ligand of the EGFR pathway, and the up-regulation of extramacrochetae, and also regulates the transcription of the sex-determining gene doublesex. The male Doublesex protein, in turn, controls extramacrochetae and spaghetti-squash expression. In females, the EGFR pathway is also down-regulated in the A7 but extramacrochetae and spaghetti-squash are not up-regulated and extrusion of precursor cells is almost absent. Our results show the complex orchestration of cellular and genetic events that lead to this important sexually dimorphic character change.
Centro de Biología Molecular Severo Ochoa (C.S.I.C.-U.A.M.), Universidad Autónoma de Madrid, Cantoblanco, Madrid, Spain.
David
D
Foronda
Paloma
P
Martín
Ernesto
E
Sánchez-Herrero
D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics* / Q000378:metabolism; D005075:Biological Evolution; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics* / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000235:genetics / Q000378:metabolism; D066246:ErbB Receptors / Q000235:genetics* / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D009024:Morphogenesis / Q000235:genetics*; D024462:Myosin Type II / Q000235:genetics / Q000378:metabolism; D011679:Pupa / Q000235:genetics* / Q000378:metabolism; D018010:Receptors, Invertebrate Peptide / Q000235:genetics* / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D012733:Sex Differentiation; D012737:Sex Factors; D015398:Signal Transduction / Q000235:genetics
D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D018398:Homeodomain Proteins; D008565:Membrane Proteins; D024462:Myosin Type II; D018010:Receptors, Invertebrate Peptide; D012097:Repressor Proteins; C062393:Abd-B proteins, Drosophila; C070369:DSX protein, Drosophila; C495593:Sqh protein, Drosophila; C063577:emc protein, Drosophila; C076026:spi protein, Drosophila; C066532:Egfr protein, Drosophila