Identification of conserved microRNAs in Bombyx mori (silkworm) and regulation of fibroin L chain production by microRNAs in heterologous system

Insect Biochem Mol Biol. 2008 Dec;38(12):1066-71. doi: 10.1016/j.ibmb.2008.09.008. Epub 2008 Oct 14.


MicroRNAs (miRNAs) are an extensive class of small non-coding RNAs with important roles in the regulation of gene expression. Little study has been performed on identifying miRNAs in Bombyx mori (silkworm). Here, 41 conserved miRNAs were identified by a computational homology search approach and some of them were selected and confirmed experimentally. Some characteristics such as position-specific nucleotide distribution, evolutionary conservation and clustered organization have been described. Through general method of miRNA target identification, we also find that at least 4 miRNAs (miR-33/-190/-276/-7) target fibroin L chain transcripts, suggesting that miRNAs might play an important role in the regulation of silk protein production. In order to validate this, 3'-UTR of fibroin L chain mRNA was cloned and several expression vectors were constructed. Assays of semi-RT-PCR, histochemical and biochemical assays after agroinfiltration indicated that miRNAs can repress reporter gene (GUS) expression with sequence complement. Clearly, agroinfiltration proved a highly efficient method to identify the function of miRNAs inhibiting their targets mRNA in heterologous system.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Base Sequence
  • Bombyx / genetics*
  • Conserved Sequence
  • Fibroins / genetics*
  • Fibroins / metabolism*
  • Gene Expression Regulation / physiology
  • Insect Proteins / genetics*
  • Insect Proteins / metabolism*
  • Larva
  • MicroRNAs / genetics*
  • Ovulation
  • Pupa


  • Insect Proteins
  • L-chain, fibroin protein, insect
  • MicroRNAs
  • Fibroins