U12 introns in unicellular eukaryotes

When U12 introns were found in plants (Wu et al. 1996, "Non-canonical introns are at least [a billion] years old" PubMed, Nature Genetics) we knew that they must have been present in the ancestors of most unicellular eukaryotes, but none had been found until now (Russell et al. 2006; PubMed, Nature). Thus, this discovery of minor spliceosomal snRNAs proteins and introns in unicellular eukaryotes was anticipated, but it is still very exciting. It will provide tools for understanding the dynamics of U12 intron loss. In addition, the early indications are that the conservation observed between plants and animals is also retained in these species, making the divergence in insects (Schneider et al. 2004; PubMed, PNAS) all the more interesting.