Drosophila Embryo: Homeotic Genes in Specification of the Anterior–Posterior Axis

Abstract

The products of the homeotic genes of Drosophila melanogaster are a set of transcription factors, each with its own unique expression pattern and battery of target genes. It is the combination of these two features by which, as a group, the homeotic genes are capable of specifying the collections of cell types characteristic of different regions of the animal body.

Keywords: embryogenesis; homeotic; homeodomain; segmental identity

Figure 1.

The organization and expression of HOM/Hox genes in Drosophilamelanogaster. The diagram shows the embryonic expression pattern and phenotypic result for the nine HOM/Hox genes. The relative chromosomal positions of the ANT‐C and BX‐C genes are shown at the bottom. The expression of each gene in a D. melanogaster embryo is shown as a colour‐coded line and shading. The lines represent the approximate extent of metameric expression domains. The shading in the embryo is representative of modulated expression patterns but is not intended to accurately depict any specific time during development. A diagram of a larva shows the diverse segmental identities produced by HOM/Hox gene expression. Ic, intercalary; Mn, mandibular; Mx, maxillary; Lb, labial; dr, dorsal ridge; T1, first thoracic; A1, first abdominal; A8, eighth abdominal; ps, posterior spiracle.

Figure 2.

The HOM/Hox homeodomains. The aligned sequences of homeodomains and flanking amino acids are shown using one letter amino acid (AA) code. The helices of the homeodomain and YPWM motif are marked. Dashes represent spaces introduced into the sequence to make the alignment, and dots represent amino acids not shown. The Abd‐B and zen homeodomains are shown separate because of their divergent homeodomains. Asterisks along the top indicate identical amino acids for the top seven homeodomains. Asterisks along the bottom mark identical amino acids for all nine homeodomains.

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Further Reading

Akam M (1998) Hox genes, homeosis and the evolution of segment identity: No need for hopeless monsters. International Journal of Developmental Biology 42: 445–451.

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Rogers, Bryan T(Apr 2001) Drosophila Embryo: Homeotic Genes in Specification of the Anterior–Posterior Axis. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0001509]