Molecular and developmental analyses of the protein encoded by the Drosophila gene ectodermal.

The Drosophila gene ectodermal (ect, located at 67D8-10 on chromosome 3) is expressed for a short period at mid-embryogenesis in all ectodermally derived tissues except the nervous system. During this stage the tissues involved form tubular structures by a process of invagination followed by cell fusion. Here we report the sequence of the ect protein as deduced from the longest ORF (280 codons) of an ect cDNA. The principal molecular features of the ect protein are: 1) a consensus leader sequence for targeting to the rough ER; 2) a central domain containing a remarkably high density of acidic residues arranged in large clusters separated by smaller clusters of hydrophobic residues; 3) a consensus nuclear-targeting sequence near the C-terminus; 4) a single tyrosine residue located at a potential tyrosine-sulfation site. The antibody staining pattern of the ect protein corresponds to the in situ hybridization pattern of the transcript. A possible role for the ect protein in the complex process of tubular formation that occurs in embryonic ectodermal tissues is discussed.