Drosophila evolution challenges postulated redundancy in the E(spl) gene complex

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 90; no. 12; pp. 5464 - 5468
• Main Authors: Maier, D, Marte, B.M, Schafer, W, Yu, Y, Preiss, A
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 15.06.1993; National Acad Sciences; National Academy of Sciences
• Subjects: Amino Acid Sequence; Animals; Biological and medical sciences; Biological Evolution; Biology; CLONACION; CLONAGE; Cloning, Molecular; Conserved Sequence; DNA; DNA probes; DROSOPHILA; Drosophila - embryology; Drosophila - genetics; DROSOPHILA MELANOGASTER; Drosophila melanogaster - embryology; Drosophila melanogaster - genetics; Embryo, Nonmammalian - physiology; Embryology: invertebrates and vertebrates. Teratology; Embryos; EVOLUCION; EVOLUTION; Evolutionary genetics; Fundamental and applied biological sciences. Psychology; Gene Expression; Genes; Genetic loci; GENETICA MOLECULAR; GENETIQUE MOLECULAIRE; Genomics; Insects; Molecular embryology; Molecular Sequence Data; Multigene Family; MUTACION; MUTATION; Neurogenesis; Restriction Mapping; RNA, Messenger - analysis; RNA, Messenger - metabolism; Sequence Homology, Amino Acid; SISTEMA NERVIOSO; SYSTEME NERVEUX; Transcription, Genetic; Helix loop helix structure; Embryonic development; Insecta; Gene organization; Nervous system; Drosophilidae; Molecular evolution; Arthropoda; Invertebrata; Locus; Drosophila melanogaster; Diptera; Drosophila hydei
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.90.12.5464

The Enhancer of split [E(spl)] gene complex belongs to the class of neurogenic loci, which, in a concerted action, govern neurogenesis in Drosophila. Two genetically distinct functions, vital and neurogenic, reside within the complex defined by lethal mutations in the l(3) gro gene and by the typical neurogenic phenotype of deletions, respectively. Such deletions always affect several of the many embryonically active genes in the region, which cannot be mutated separately to lethality. Seven of these genes are extremely similar at the transcription and sequence level sharing the basic helix-loop-helix (bHLH) motif of transcriptional regulators. While these E(spl) bHLH genes seem to be required collectively for neurogenesis, they are nonessential individually, suggesting functional redundancy of the encoded gene products. No specific functions could yet be ascribed to any of the other genes located within the complex. One might expect these apparently dispensable genes, as well as the supposedly redundant bHLH genes, to be under little evolutionary constraint and, thus, to evolve most rapidly. However, we find the entire E(spl) gene complex highly conserved during Drosophila evolution, indicating that all the genes as well as their organization are of functional importance.