Developmentally Regulated Splicing of the Third Intron of P Element in Somatic Tissues in Drosophila Embryos: (transposon/P element/splicing/Drosophila embryo).

In Drosophila, it has been suggested that the third intron of the P element is spliced out only in germ-line cells. However, we found that the splicing took place in some somatic tissues during embryogenesis, as well as in pole cells, progenitor cells of the germ line. To detect the splicing activity in vivo, we designed an assay system to visualize the cells where the third intron was spliced out by the histochemical staining for β-galactosidase activity. In this paper, we describe the somatic tissues where the third intron is spliced out during embryogenesis, with reference to the stages when the splicing occurs. Based on these findings we propose a modification of the previous documentation that the complete processing of transcripts from P element takes place only in germ-line cells.