Structural relationships among genes that control development: sequence homology between the Antennapedia, Ultrabithorax, and fushi tarazu loci of Drosophila.

TLDR

In Drosophila melanogaster, developmental genes are organized into tightly linked clusters, notably the bithorax complex (BX‑C) and Antennapedia complex (ANT‑C), each containing homeotic loci whose mutations cause segment transformations, while the fushi tarazu locus regulates embryonic segmentation. The authors mapped repetitive DNA, including a transposon, within ANT‑C and performed cross‑hybridization of 3′ exons from Antennapedia, Ultrabithorax, and fushi tarazu, revealing weak but detectable sequence similarity among the loci. Sequence analysis of the cross‑hybridizing DNA uncovered conserved predicted amino‑acid motifs, indicating that two homeotic loci and the segment‑deficient fushi tarazu locus encode proteins with partially shared structures and are likely evolutionarily and functionally related.

Abstract

Genes that regulate the development of the fruit fly Drosophila melanogaster exist as tightly linked clusters in at least two cases. These clusters, the bithorax complex (BX-C) and the Antennapedia complex (ANT-C), both contain multiple homoeotic loci: mutations in each locus cause a transformation of one part of the fly into another. Several repetitive DNA sequences, including at least one transposon, were mapped in the ANT-C. DNA from the 3' exon of Antennapedia (Antp), a homoeotic locus in the ANT-C, hybridized weakly to DNA from the 3' exon of Ultrabithorax (Ubx), a homoeotic locus in the BX-C. DNA from each of these 3' exons also hybridized weakly to DNA from the fushi tarazu locus of the ANT-C. The fushi tarazu (ftz) locus controls the number and differentiation of segments in the developing embryo. Sequence analysis of the cross-hybridizing DNA from the three loci revealed the conservation of predicted amino acid sequences derived from coding parts of the genes. This suggests that two homoeotic loci and a "segment-deficient" locus encode protein products with partially shared structures and that the three loci may be evolutionarily and functionally related.