Cross-regulatory interactions among tracheal genes support a co-operative model for the induction of tracheal fates in the Drosophila embryo.
The Drosophila tracheal system arises from clusters of ectodermal cells that invaginate and migrate to originate a network of epithelial tubes. Genetic analyses have identified several genes that are specifically expressed in the tracheal cells and are required for tracheal development. Among them, trachealess (trh) is able to induce ectopic tracheal pits and therefore it has been suggested that it would act as an inducer of tracheal cell fates; however, this capacity appears to be spatially restricted. Here we analyze the expression of the tracheal specific genes in the early steps of tracheal development and their cross-interactions. We find that there is a set of primary genes including trh and ventral veinless (vvl) whose expression does not depend on any other tracheal gene and a set of downstream genes whose expression requires different combinations of the primary genes. We also find that the combined expression of primary genes is sufficient to induce some downstream genes but not others. These results indicate that there is not a single master gene responsible for the appropriate expression of the tracheal genes and support a model where tracheal cell fates are induced by the co-operation of several factors rather than by the activity of a single tracheal inducer.
Boube
M
M
Institut de Biologia Molecular de Barcelona (CSIC), C/Jordi Girona 18-26, 08034, Barcelona, Spain.
Llimargas
M
M
Casanova
J
J
D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology; D015536:Down-Regulation; D004330:Drosophila / Q000196:embryology* / Q000235:genetics; D029721:Drosophila Proteins; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics* / Q000502:physiology; D019476:Insect Proteins / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics*; D050809:POU Domain Factors; D011505:Protein-Tyrosine Kinases; D017468:Receptors, Fibroblast Growth Factor / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics; D014132:Trachea / Q000196:embryology; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D019476:Insect Proteins; D008565:Membrane Proteins; D009687:Nuclear Proteins; D050809:POU Domain Factors; D017468:Receptors, Fibroblast Growth Factor; D012097:Repressor Proteins; C081481:Rho protein, Drosophila; C472498:Stet protein, Drosophila; D014157:Transcription Factors; C108529:apt protein, Drosophila; C074089:kni protein, Drosophila; C089211:knrl protein, Drosophila; C106513:peb protein, Drosophila; C085793:salm protein, Drosophila; C115576:stumps protein, Drosophila; C099995:trh protein, Drosophila; C091575:vvl protein, Drosophila; C102301:BTL protein, Drosophila; D011505:Protein-Tyrosine Kinases