Functional and ecological significance of rDNA intergenic spacer variation in a clonal organism under divergent selection for production rate

Elena Gorokhova, Thomas E. Dowling, Lawrence J. Weider, Teresa J. Crease, James Elser

Research output: Contribution to journalArticle

68 Scopus citations

Abstract

It has recently been hypothesized that variation in the intergenic spacer (IGS) of rDNA has considerable developmental, evolutionary and ecological significance through effects on growth rate and body C: N: P stoichiometry resulting from the role of the IGS in production of rRNA. To test these ideas, we assessed changes in size and structure of the repetitive region of the IGS, juvenile growth rate (JGR), RNA and phosphorus (P) contents in clonal lineages of Daphnia pulex derived from a single female and subjected to divergent selection on weight-specific fecundity (WSF). As a result of selection, WSF diverged rapidly, with significant reductions within two generations. Other significant changes accompanying shifts in WSF were that juveniles produced by low-WSF females grew more rapidly and had higher RNA and P contents. An increased predominance of long IGS variants was observed in lineages with elevated JGRs and low WSF. The observed variations in IGS length were related to the number of subrepeat units carrying a promoter sequence in the repetitive region. These results strongly support the hypothesized relationships, indicate a genetic mechanism for the evolution of such associations and demonstrate that Daphnia (and perhaps other parthenogens) possess considerable potential for rapid adaptive change in major life-history traits.

Original languageEnglish (US)
Pages (from-to)2373-2379
Number of pages7
JournalProceedings of the Royal Society B: Biological Sciences
Volume269
Issue number1507
DOIs
StatePublished - Nov 22 2002

Keywords

  • Asexual lineages
  • Daphnia
  • Growth rate
  • Phosphorus
  • RNA
  • rDNA intergenic spacer structure

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)
  • Environmental Science(all)
  • Agricultural and Biological Sciences(all)

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