The Drosophila Pax gene eye gone is required for embryonic salivary duct development

What are the developmental mechanisms required for conversion of an undiffe rentiated, two-dimensional field of cells into a patterned, tubular organ? In this report, we describe the contribution of the Drosophila Pax gene eye gone to the development of the embryonic salivary glands and ducts. eye go ne expression in salivary tissues is controlled by several known regulators of salivary fate, After the initial establishment of the salivary primordi um by Sex combs reduced, fork head excludes eye gone expression from the pr egland cells so that its salivary expression is restricted to the posterior preduct cells. trachealess, in contrast, activates eye gone expression in the posterior preduct cells. We have previously described the process by wh ich fork head and the EGF receptor pathway define the border between the gl and and duct primordia, Here we show that eye gone is required for the subd ivision of the duct primordium itself into the posterior individual duct an d the anterior common duct domains. In the absence of eye gone, individual ducts as well as the precursor of the adult salivary glands, the imaginal r ing, are absent. We took advantage of this ductless phenotype to show that Drosophila larvae do not have an obligate requirement for salivary glands a nd ducts, In addition to its role in the salivary duct, eye gone is require d in the embryo for the development of the eye-antennal imaginal disc and t he chemosensory antennal organ.