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Evolution of microRNAs and their targets: are all microRNAs biologically relevant?

Michael J Axtell1

  • 1Department of Biology, Pennsylvania State University, University Park, PA 16802, USA. mja18@psu.edu

Biochimica Et Biophysica Acta
|March 18, 2008
PubMed

Insights

Plant microRNAs (miRNAs) exhibit diverse evolutionary patterns. While some are conserved and regulate development, many are transient, potentially serving as a reservoir for future regulatory innovation.

Area of Science:

  • Molecular Biology
  • Evolutionary Biology
  • Genetics

Background:

  • MicroRNAs (miRNAs) are key regulators processed from stem-loop precursors, distinct from their targets.
  • Evidence suggests miRNAs originated multiple times in eukaryotes from ancestral small RNA machinery.
  • Plant miRNAs show a dichotomy: highly conserved, developmental regulators versus transient, weakly expressed ones.

Purpose of the Study:

  • To explore the evolutionary origins and functional diversity of plant microRNAs.
  • To differentiate between conserved and transient microRNA populations in plants.
  • To investigate the potential role of transient microRNAs in evolutionary innovation.

Main Methods:

  • Comparative genomics to identify conserved miRNA families and their targets.
  • Expression analysis to distinguish between highly and weakly expressed miRNA populations.
  • Phylogenetic analysis to infer evolutionary histories of plant miRNAs.

Main Results:

  • A subset of plant miRNAs are strongly expressed, conserved across species, and target DNA-binding transcription factors involved in development.
  • A larger group of plant miRNAs are weakly expressed, poorly conserved, and have few identifiable targets, termed 'transient' miRNAs.
  • Transient miRNAs may represent an evolutionary reservoir, with new regulatory functions potentially selected over time.

Conclusions:

  • Plant miRNA evolution is characterized by both stable, conserved regulatory pathways and dynamic, transient populations.
  • Transient microRNAs, despite low apparent selective value, may contribute to evolutionary adaptability by providing novel regulatory elements.
  • Understanding the dual nature of plant miRNAs is crucial for deciphering gene regulation and evolutionary processes in plants.

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