Evolution of the interaction between Hox genes and a downstream target.
Segmental identities along the insect body depend on the activities of Hox genes [1,2]. In Drosophila melanogaster, one well-studied Hox regulatory target is Distal-less (Dll), which is required for the development of distal limb structures [3]. In abdominal segments, Dll transcription is prevented when Hox proteins of the Bithorax Complex (BX-C) bind to cis-regulatory elements upstream of the Dll transcription start site [4,5]. Previous evolutionary comparisons of gene expression patterns suggest that this direct repression is conserved between Diptera and Lepidoptera, but is absent in the Crustacea [6,7]. We examined gene expression patterns in three orders of hexapods, all of which develop abdominal appendages, in order to determine when the strong repressive interaction between BX-C proteins and Dll appeared during evolution. In each of the species examined, Dll expression was initiated in abdominal cells despite the presence of high levels of BX-C proteins. It appears that the strong repressive effects of BX-C proteins on Dll expression arose relatively late in insect evolution. We suggest that the regulatory interaction between the BX-C genes and Dll has evolved within the hexapods in a complex, segment-specific manner.
Palopoli
M F
MF
Howard Hughes Medical Institute, University of Chicago, Illinois 60637, USA.
Patel
N H
NH
D000818:Animals; D005075:Biological Evolution; D001517:Coleoptera / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics*; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000235:genetics; D015870:Gene Expression; D005801:Genes, Homeobox; D017344:Genes, Insect; D018398:Homeodomain Proteins / Q000235:genetics*; D019476:Insect Proteins / Q000235:genetics*; D007313:Insecta / Q000235:genetics; D009687:Nuclear Proteins; D009987:Orthoptera / Q000235:genetics; D014157:Transcription Factors
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D019476:Insect Proteins; D009687:Nuclear Proteins; D014157:Transcription Factors; C066177:Ubx protein, Drosophila; C066591:abd-A protein, Drosophila