The expression of the let-7 small regulatory RNA is controlled by ecdysone during metamorphosis in Drosophila melanogaster

Dev Biol. 2002 Apr 1;244(1):170-9. doi: 10.1006/dbio.2002.0594.


In Caenorhabditis elegans, the heterochronic pathway controls the timing of developmental events during the larval stages. A component of this pathway, the let-7 small regulatory RNA, is expressed at the late stages of development and promotes the transition from larval to adult (L/A) stages. The stage-specificity of let-7 expression, which is crucial for the proper timing of the worm L/A transition, is conserved in Drosophila melanogaster and other invertebrates. In Drosophila, pulses of the steroid hormone 20-hydroxyecdysone (ecdysone) control the timing of the transition from larval to pupal to adult stages. To test whether let-7 expression is regulated by ecdysone in Drosophila, we used Northern blot analysis to examine the effect of altered ecdysone levels on let-7 expression in mutant animals, organ cultures, and S2 cultured cells. Experiments were conducted to test the role of Broad-Complex (BR-C), an essential component in the ecdysone pathway, in let-7 expression. We show that ecdysone and BR-C are required for let-7 expression, indicating that the ecdysone pathway regulates the temporal expression of let-7 in Drosophila. These results demonstrate an interaction between steroid hormone signaling and the heterochronic pathway in insects.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • DNA Primers
  • Drosophila melanogaster / drug effects
  • Drosophila melanogaster / genetics*
  • Drosophila melanogaster / growth & development
  • Ecdysone / pharmacology*
  • Ecdysterone / pharmacology*
  • Gene Expression Regulation, Developmental / drug effects*
  • Larva
  • Metamorphosis, Biological / drug effects
  • Metamorphosis, Biological / genetics*
  • Oligodeoxyribonucleotides, Antisense / genetics
  • Pupa
  • RNA, Helminth / genetics*
  • RNA, Small Nuclear / genetics*
  • Signal Transduction
  • Transcription, Genetic / drug effects


  • DNA Primers
  • Oligodeoxyribonucleotides, Antisense
  • RNA, Helminth
  • RNA, Small Nuclear
  • Ecdysone
  • Ecdysterone