Eukaryotic evolution

Early origin of canonical introns

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Spliceosomal introns, one of the hallmarks of eukaryotic genomes, were thought to have originated late in evolution1,2 and were assumed not to exist in eukaryotes that diverged early — until the discovery of a single intron with an aberrant splice boundary in the primitive 'protozoan' Giardia3. Here we describe introns from a close relative of Giardia, Carpediemonas membranifera, that have boundary sequences of the normal eukaryotic type, indicating that canonical introns are likely to have arisen very early in eukaryotic evolution.

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Figure 1: Introns and evolutionary affinities of Carpediemonas.


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Correspondence to Alastair G. B. Simpson.

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The authors declare no competing financial interests.

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Simpson, A., MacQuarrie, E. & Roger, A. Early origin of canonical introns. Nature 419, 270 (2002) doi:10.1038/419270a

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