six-banded, a novel Drosophila gene, is expressed in 6 segmental stripes during embryonic development and in the eye imaginal disc.

We have characterised a Drosophila P-element enhancer detector insertion F125, which is expressed in the embryonic head and CNS as well as in various third instar imaginal discs. In an attempt to identify the gene with the equivalent expression pattern, we have characterised an adjacent gene. It encodes two novel conceptual proteins: Type I (1182 amino acids) and Type II, representing a shorter form of 774 amino acids truncated at both termini relative to Type I that is generated by alternative splicing. Based on its embryonic expression pattern, the gene was called six-banded (sba). Both splice forms are expressed in a unique embryonic pattern: initially as 6, then 12 stripes during early stages of embryonic development. Subsequently, expression is found in the developing trachae and during larval development is restricted to the eye imaginal disc where both transcripts are present immediately anterior to and behind the morphogenetic furrow. While sba expression in the eye antennal disc is mirrored by the expression of the adjacent F125 P-element, other patterns reported by this enhancer detector are not mimicked by the sba gene suggesting that the expression of the P-element represents a 'composite' of the effects of nearby enhancers.