Common and diverged functions of the Drosophila gene pair D-Sp1 and buttonhead

The Drosphila gene buttonhead (btd) is required for the formation of the ma ndibular, the intercalary and the antennal head segments of the embryo. The btd protein (BTD) is functionally and structurally related to the human C2 H2 zinc finger transcription factor Sp 1. A second Sp1-like Drosophila gene , termed Drosophila Sp1 (D-Spl), had been identified on the basis of a part ial sequence showing that the gene encodes a characteristic zinc finger dom ain, composed of three finger motifs similar to both Spl and btd. D-Spl is located in the same cytological location as btd in chromosome band 9A on th e X-chromosome. It had bren proposed that D-Spl and btd are likely to act a s a gene pair and function in a at least partially redundant manner. Here w e report the molecular analysis of D-Spl and its expression pattern during embryonic and larval development. We show that D-Spl acts as a transcriptio nal regulator. Lack-of-function analysis combined with rescue and gain-of-f unction studies indicates that btd and D-Spl play essential and redundant r oles for mechanosensory organ development. However, D-Spl lacks the specifi c features of BTD required for embryonic intercalary and antennal segment f ormation. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.