A miRNA involved in phosphate-starvation response in Arabidopsis

Curr Biol. 2005 Nov 22;15(22):2038-43. doi: 10.1016/j.cub.2005.10.016.


Although microRNAs (miRNAs) have been documented to regulate development in plants and animals , the function of miRNAs in physiology is unclear. miR399 has multiple target sites in the 5' untranslated region (UTR) of a gene encoding a putative ubiquitin-conjugating enzyme (UBC) in Arabidopsis thaliana. We report here that miR399 was highly induced, whereas the target UBC mRNA was reduced by low-phosphate (Pi) stress. In transgenic plants with constitutive expression of miR399, UBC mRNA accumulation was suppressed even under high Pi. The expression of transgene UBC mRNA with 5' UTR miR399 target sites, but not the one without 5' UTR, was reduced under low-Pi condition. Furthermore, transgenic Arabidopsis plants with constitutive expression of miR399 accumulated more Pi than the wild-type, and transgenic plants expressing the UBC mRNA without 5' UTR (miRNA-deregulated) showed less inhibition of primary root growth and less induction of a Pi transporter gene by low-Pi stress than those of wild-type plants. We conclude that miR399 downregulates UBC mRNA accumulation by targeting the 5' UTR, and this regulation is important for plant responses to Pi starvation. The results suggest that miRNAs have functional roles for plants to cope with fluctuations in mineral-nutrient availability in the soil.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adaptation, Physiological / physiology*
  • Arabidopsis / metabolism
  • Arabidopsis / physiology*
  • Blotting, Northern
  • DNA Primers
  • Gene Expression Regulation, Enzymologic*
  • Gene Expression Regulation, Plant*
  • MicroRNAs / genetics
  • MicroRNAs / metabolism*
  • Mutagenesis, Site-Directed
  • Phenotype*
  • Phosphates / deficiency
  • Phosphates / metabolism
  • Plant Roots / growth & development
  • Plants, Genetically Modified
  • Polymerase Chain Reaction
  • Ubiquitin-Conjugating Enzymes / genetics
  • Ubiquitin-Conjugating Enzymes / metabolism*


  • DNA Primers
  • MicroRNAs
  • Phosphates
  • Ubiquitin-Conjugating Enzymes