senseless is necessary for the survival of embryonic salivary glands in Drosophila

Apoptosis in developing Drosophila embryos is rare and confined to specific groups of cells. We explain how one organ, salivary glands, of Drosophila embryos avoids apoptosis. senseless (sens), a Zn-finger transcription factor, is expressed in the salivary primordium and later in the differentiated salivary glands. The regulation of sens expression in the salivary placodes is more complex than observed in the embryonic PNS. We have shown that sens expression is initiated in the salivary placodes by fork head (fkh), a winged helix transcription factor. The expression of sens is maintained in the salivary glands by fkh and by daughterless (da), a bHLH family member. In this study, we have identified sage, a salivary-specific bHLH protein as a new heterodimeric partner for da protein in the salivary glands. In addition, our data suggest that sage RNAi embryos have a phenotype similar to sens and that sage is necessary to maintain expression of sens in the embryonic salivary glands. Furthermore, we show that in the salivary glands, sens acts as an anti-apoptotic protein by repressing reaper and possibly hid.