Redundant mechanisms mediate bristle patterning on the Drosophila thorax.
The thoracic bristle pattern of Drosophila results from the spatially restricted expression of the achaete-scute (ac-sc) genes in clusters of cells, mediated by the activity of many discrete cis-regulatory sequences. However, ubiquitous expression of sc or asense (ase) achieved with a heterologous promoter, in the absence of endogenous ac-sc expression, and the activity of the cis-regulatory elements, allows the development of bristles positioned at wild-type locations. We demonstrate that the products of the genes stripe, hairy, and extramacrochaetae contribute to rescue by antagonizing the activity of Sc and Ase. The three genes are expressed in specific but overlapping spatial domains of expression that form a prepattern that allows precise positioning of bristles. The redundant mechanisms might contribute to the robustness of the pattern. We discuss the possibility that patterning in trans by antagonism is ancestral and that the positional cis-regulatory sequences might be of recent origin.
Usui
Kazuya
K
Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK.
Goldstone
Claire
C
Gibert
Jean-Michel
JM
Simpson
Pat
P
D000818:Animals; D019521:Body Patterning / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics; D004330:Drosophila; D029721:Drosophila Proteins / Q000235:genetics; D004742:Enhancer Elements, Genetic; D018507:Gene Expression Regulation, Developmental; D017344:Genes, Insect; D006197:Hair; D009419:Nerve Tissue Proteins / Q000235:genetics; D013909:Thorax; D014157:Transcription Factors / Q000235:genetics
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D009419:Nerve Tissue Proteins; D014157:Transcription Factors; C407353:ase protein, Drosophila; C089197:sc protein, Drosophila