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Chemical Communication in a Post-Genomic World (2003) / Chapter Skim
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7 Molecular evolution of the insect chemoreceptor gene superfamily in Drosophila melanogaster
Pages 25-30

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From page 25...
... Phylogenetic analysis reveals deep branches connecting multiple highly divergent clades within the Gr family, and the Or family appears to be a single highly expanded lineage within the superfamily. The genes are spread throughout the Drosophila genome, with some relatively recently diverged genes still clustered in the genome.
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From page 26...
... In the original Celera Genomics scaffold sequences, there were two identical copies of Orl9a in inverted orientation ~50 kb apart; however, resequencing of the genome by the Berkeley Drosophila Genome Project showed that these copies differ at seven nucleotide positions, yielding three changes in amino acid sequence; the proximal gene retains the Orl9a name, and the distal gene we have named Orl 9b. The duplication extends ~850 bp beyond the predicted N termini and ~700 bp beyond the predicted C termini.
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From page 27...
... , which commonly are highly clustered on particular chromosomes, in part reflecting the relatively recent expansions of these chemoreceptor families. The ancestral and idiosyncratic intron locations within the coding regions of the Or genes are shown schematically in Fig.
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From page 28...
... The tree is rooted at the midpoint. The Or and Gr families are indicated on the right, and the scale bar indicates 50% divergence in corrected distancesffarlargerthantheuncorrected distanceswhen comparing distantly related proteins)
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From page 29...
... These genes share five idiosyncratic introns and are highly divergent from other receptors within the family. In contrast, the GrS8a-c genes are adjacent to each other, yet only GrS8a/b weakly cluster in the tree, and all three share as little amino acid similarity with each other as many other pairs of Gr proteins (11-16%~.
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From page 30...
... 36J. The ancestral insect chemoreceptor genes appear to have had only three phase 0 introns near their C termini.
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Key Terms

  • insect chemoreceptor
  • drosophila genome
  • chemoreceptor superfamily
  • highly divergent
  • odorant receptor

  • phylogenetic analysis
  • celera genomics
  • final exon
  • related proteins
  • exon encoding

  • situ hybridization
  • molecular evolution
  • acid identity
  • genes appear
  • maxillary palp

  • exons encoding
  • idiosyncratic introns
  • intron losses
  • intron locations
  • amino acids

  • transmembrane domains
  • van der
  • relatively recent
  • single genes
  • previously undescribed

  • supporting information
  • relatively recently
  • olfactory organs
  • pseudoobscura genome
  • encoding transmembrane


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