Cell fate specification in the Drosophila salivary gland: the integration of homeotic gene function with the DPP signaling cascade.
Salivary gland formation in the Drosophila embryo is linked to the expression of the homeotic gene Sex combs reduced (Scr). When Scr function is missing, salivary glands do not form, and when SCR is expressed everywhere, salivary glands form in new places. However, not every cell that expresses Scr is recruited to a salivary gland fate. Along the anterior-posterior axis, the posteriorly expressed proteins encoded by the teashirt (tsh) and Abdominal-B (Abd-B) genes block SCR activation of salivary gland genes, and along the dorsal-ventral axis, the secreted signaling molecule encoded by decapentaplegic (dpp) prevents activation of salivary gland genes by SCR in dorsal regions of parasegment 2. We have identified five downstream components in the DPP signaling cascade required to block salivary gland gene activation. These components include two known receptors, the type I receptor encoded by the thick veins (tkv) gene and the type II receptor encoded by the punt (put) gene; two of the four known Drosophila members of the Smad family of proteins which transduce signals from the receptors to the nucleus, Mothers against dpp (Mad) and Medea (Med); and, finally, a large zinc-finger transcription factor encoded by the schnurri (shn) gene. These results reveal how anterior-posterior and dorsal-ventral patterning information is integrated at the level of organ-specific gene expression.
Henderson
K D
KD
Department of Cell Biology and Anatomy, The Johns Hopkins University School of Medicine, Baltimore, Maryland, 21205-2196, USA.
Isaac
D D
DD
Andrew
D J
DJ
D000818:Animals; D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000196:embryology* / Q000235:genetics*; D004625:Embryo, Nonmammalian / Q000502:physiology; D004627:Embryonic Induction; D005260:Female; D018507:Gene Expression Regulation, Developmental; D019476:Insect Proteins / Q000235:genetics* / Q000502:physiology*; D008297:Male; D008954:Models, Biological; D009024:Morphogenesis; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000502:physiology; D011956:Receptors, Cell Surface / Q000235:genetics / Q000502:physiology; D012469:Salivary Glands / Q000166:cytology / Q000196:embryology*; D015398:Signal Transduction; D051898:Smad1 Protein; D014157:Transcription Factors; D015533:Transcriptional Activation; D029867:Xenopus Proteins; D015053:Zygote / Q000502:physiology
D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D019476:Insect Proteins; C111712:MEA protein, Arabidopsis; D010940:Plant Proteins; D011956:Receptors, Cell Surface; C000607853:SMAD1 protein, Xenopus; C059627:Scr protein, Drosophila; D051898:Smad1 Protein; D014157:Transcription Factors; D029867:Xenopus Proteins; C064196:dpp protein, Drosophila; C090169:tkv protein, Drosophila; D017346:Protein Serine-Threonine Kinases