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Nuclear processing and export of microRNAs in Arabidopsis

Mee Yeon Park1, Gang Wu, Alfredo Gonzalez-Sulser

  • 1Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6018, USA.

Proceedings of the National Academy of Sciences of the United States of America
|March 2, 2005
PubMed

Insights

Arabidopsis HASTY protein exports microRNAs (miRNAs) but not tRNAs. This suggests distinct nuclear export pathways for small RNAs in plants, unlike in mammals.

Area of Science:

  • Plant molecular biology
  • RNA biogenesis and export
  • Small RNA pathways

Background:

  • Exportin 5 (Exp5) in mammals exports pre-microRNAs (pre-miRNAs) and tRNAs.
  • HASTY (HST) is the Arabidopsis ortholog of Exportin 5.
  • Nuclear export mechanisms for small RNAs in plants are not fully understood.

Purpose of the Study:

  • To investigate the function of HASTY (HST) in Arabidopsis miRNA and tRNA biogenesis.
  • To determine if HST and Exportin-t ortholog PAUSED (PSD) share RNA cargos for nuclear export.
  • To elucidate nuclear export pathways for small RNAs in plants.

Main Methods:

  • Analysis of loss-of-function mutations in HASTY (HST) and PAUSED (PSD) genes.
  • Quantification of small RNA accumulation (miRNAs, tRNAs, siRNAs) in Arabidopsis mutants.
  • Assessment of transgene silencing and tRNA processing.

Main Results:

  • Arabidopsis miRNAs are single-stranded in the nucleus.
  • HST loss-of-function mutations reduced miRNA accumulation but not tRNA or siRNA accumulation.
  • PSD mutation affected tRNA-Tyr processing but not miRNA accumulation or export.

Conclusions:

  • HST and PSD do not share RNA cargos for nuclear export in Arabidopsis.
  • Distinct nuclear export pathways exist for different small RNA classes in plants.
  • These findings highlight differences in small RNA export between plants and mammals.

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