The Role of HOM-C Genes in Segmental Transformations: Reexamination of theDrosophila Sex combs reducedEmbryonic Phenotype

• Published in: Developmental biology Vol. 180; no. 1; pp. 131 - 142
• Main Authors: Pederson, Julie D., Kiehart, Daniel P., Mahaffey, James W.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 25-11-1996
• ISSN: 0012-1606; 1095-564X
• DOI: 10.1006/dbio.1996.0290

Homeotic genes in the Antennapedia Complex ofDrosophilaspecify identity of the posterior head segments; the labial segment requiresSex combs reduced(Scr) for proper development,Deformed(Dfd) specifies maxillary and mandibular identity, andlabialis necessary for intercalary segment identity. Although mutations in these genes cause homeotic transformations during imago development, the only obvious homeotic transformation during embryonic head development is found inScrmutants, where a partial transformation of the labial segment to a more anterior, maxillary identity has been reported. This transformation is unusual because DFD protein does not accumulate in the labial cells ofScrmutants, although DFD is required for development of maxillary structures. Here, we present evidence that casts doubt on whether the labial to maxillary transformation actually exists in embryos lackingScr.The observed morphological characteristics and gene expression patterns of various mutant embryos indicate a loss of segmental identity rather than a transformation.