Ribosomal DNA in the grasshopper Podisma pedestris: Escape from concerted evolution

I Keller, I C Chintauan-Marquier, Paris Veltsos, R A Nichols

Research output: Contribution to journalArticlepeer-review

69 Citations (Scopus)

Abstract

Eukaryote nuclear ribosomal DNA (rDNA) typically exhibits strong concerted evolution: a pattern in which several hundred rDNA sequences within any one species show little or no genetic diversity, whereas the sequences of different species diverge. We report a markedly different pattern in the genome of the grasshopper Podisma pedestris. Single individuals contain several highly divergent ribosomal DNA groups. Analysis of the magnitude of divergence indicates that these groups have coexisted in the Podisma lineage for at least 11 million years. There are two putatively functional groups, each estimated to be at least 4 million years old, and several pseudogene groups, many of which are transcribed. Southern hybridization and real-time PCR experiments show that only one of the putatively functional types occurs at high copy number. However, this group is scarcely amplified under standard PCR conditions, which means that phylogenetic inference on the basis of standard PCR would be severly distorted. The analysis suggests that concerted evolution has been remarkably ineffective in P. pedestris. We propose that this outcome may be related to the species' exceptionally large genome and the associated low rate of deletion per base pair, which may allow pseudogenes to persist.

Original languageEnglish
Pages (from-to)863-874
Number of pages12
JournalGenetics
Volume174
Issue number2
DOIs
Publication statusPublished - Oct 2006

Keywords

  • CHORTHIPPUS-PARALLELUS
  • PHYLOGENETIC ANALYSIS
  • MAXIMUM-LIKELIHOOD
  • BAYESIAN-INFERENCE
  • STATISTICAL TESTS
  • CHROMOSOMAL CLINE
  • INTERGENIC SPACER
  • GENE CONVERSION
  • SEX-CHROMOSOME
  • SEQUENCES

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