Sequence and expression of two regulated transcription units during Drosophila melanogaster development: Deb-A and Deb-B

Two transcription units, Deb-A and Deb-B (developmental embryonic), are present in a recombinant bacteriophage clone containing a DNA insert from Drosophila melanogaster. The insert maps cytologically to chromosome 2R at 48EF. Sequence analysis of the open reading frames indicates that both are putative membrane proteins with similar hydropathy profiles. The expression of the encoded poly(A)⁺ RNAs is regulated during oocyte embryonic and larval development. The 600 base Deb-A RNA is present in oocytes and increases in abundance until 15 h of embryogenesis. Its abundance level drops dramatically between 15 and 19 h and is modulated at a low level in the three larval instars and pupae. The 525 base Deb-B RNA is present in oocytes at a 10-fold lower level than the Deb-A transcript. Its abundance increases until a maximum level is reached at 9-12 h. After this time the transcript is undetectable on Northern transfers. Both RNAs are present in greater than 95% polyadenylated form in the cytoplasm. Deb-B RNA is found on polysomes in proportions similar to the bulk of poly(A)⁺ RNA populations. Deb-A RNA, on the other hand is mostly nonpolysomal during embryogenesis. The RNAs from both Deb-A and Deb-B are found uniformly distributed throughout the embryo during development.