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Related Experiment Videos

Intron phylogeny: a new hypothesis.

T Cavalier-Smith1

  • 1Department of Botany, University of British Columbia, Vancouver, Canada.

Trends in Genetics : TIG
|May 1, 1991
PubMed
Summary
This summary is machine-generated.

Introns, the non-coding DNA sequences, evolved at different times. Structured introns are ancient, while spliceosomal introns arose later with the nucleus and mitochondria.

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Area of Science:

  • Molecular Biology
  • Evolutionary Biology
  • Genetics

Background:

  • Introns are non-coding sequences within genes that are removed during RNA processing.
  • Three major classes of introns exist: structured (group I), protein-spliced, and spliceosomal.
  • The evolutionary history and relative antiquity of these intron classes are not fully understood.

Purpose of the Study:

  • To investigate the evolutionary timeline of the three major intron classes.
  • To determine the relative ages and origins of structured, protein-spliced, and spliceosomal introns.
  • To correlate intron evolution with major cellular events like the origin of the nucleus and mitochondria.

Main Methods:

  • Comparative analysis of intron structures and splicing mechanisms.

Related Experiment Videos

  • Phylogenetic reconstruction of intron origins.
  • Integration of molecular clock estimates with known cellular evolutionary events.

    • Main Results:

    • Structured introns (e.g., group I) are the most ancient, originating ~3.5 billion years ago in eubacterial ancestors, initially in tRNA.
    • Protein-spliced introns evolved from structured introns ~1.7 billion years ago in the common ancestor of eukaryotes and archaea, also primarily in tRNA.
    • Spliceosomal introns evolved from group II-like introns after the nucleus formed (~1.7-1.0 billion years ago) and were inserted into protein-coding genes post-mitochondria origin (~1.0 billion years ago).

    Conclusions:

    • The three major intron classes exhibit unequal evolutionary ages, reflecting distinct origins and diversification timelines.
    • Intron evolution is closely linked to major transitions in cellular life, including the emergence of eukaryotes, the nucleus, and mitochondria.
    • Understanding intron antiquity provides insights into the early evolution of gene expression and genome complexity.