Salivary duct determination in Drosophila: roles of the EGF receptor signalling pathway and the transcription factors fork head and trachealess.
Organogenesis in Drosophila embryos begins at 4-5 hours of development as the expression of organ-specific genes is initiated. The salivary primordium, which occupies the ventral epidermis of parasegment 2, is among the earliest to be defined. It is soon divided into two distinct regions: the more dorsal pregland cells and the more ventral preduct cells. We show that it is the opposing activities of the Drosophila EGF receptor (DER) signaling pathway and the Fork head transcription factor that distinguish these cell types and set up the boundary between them. DER signaling acts ventrally to block fork head expression in the preduct cells, thereby restricting gland identity to the more dorsal cells. Fork head in turn blocks expression of duct-specific genes in the pregland cells, thereby restricting duct identity to the more ventral cells. A third regulatory activity, the Trachealess transcription factor, is also required to establish the identity of the preduct cells, but we show that it acts independently or downstream from the DER:fork head confrontation. In trachealess mutants, subdivision of the salivary primordium occurs normally and the dorsal cells form glands, but the ventral cells are undetermined. We present a model proposing that trachealess is the crucial duct-specific gene that Fork head represses to distinguish pregland from preduct cells.
Kuo
Y M
YM
Department of Molecular and Cell Biology, Division of Genetics, University of California, Berkeley, 94720, USA.
Jones
N
N
Zhou
B
B
Panzer
S
S
Larson
V
V
Beckendorf
S K
SK
D000818:Animals; D002135:Calcium-Binding Proteins; D004268:DNA-Binding Proteins; D004330:Drosophila / Q000196:embryology* / Q000235:genetics; D029721:Drosophila Proteins; D004815:Epidermal Growth Factor; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D051858:Forkhead Transcription Factors; D018507:Gene Expression Regulation, Developmental; D036341:Intercellular Signaling Peptides and Proteins; D000072100:Jagged-1 Protein; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D009024:Morphogenesis; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D011494:Protein Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D018010:Receptors, Invertebrate Peptide / Q000235:genetics / Q000378:metabolism*; D018987:Salivary Ducts / Q000196:embryology; D000072099:Serrate-Jagged Proteins; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*
D002135:Calcium-Binding Proteins; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D051858:Forkhead Transcription Factors; D036341:Intercellular Signaling Peptides and Proteins; D000072100:Jagged-1 Protein; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D018010:Receptors, Invertebrate Peptide; C000606278:Ser protein, Drosophila; D000072099:Serrate-Jagged Proteins; D014157:Transcription Factors; C083884:pnt protein, Drosophila; C099995:trh protein, Drosophila; C076026:spi protein, Drosophila; D004815:Epidermal Growth Factor; D011494:Protein Kinases; C066532:Egfr protein, Drosophila; D066246:ErbB Receptors