Intron polymorphisms: sometimes there, sometimes not
Up until now, biologists believed that within a species, an intron is either fixed or not present at a particular point in a gene. The plant pathologists were surprised, therefore, to discover that M. graminicola deviated from the conventional model. The intron was present in some individuals and absent in others. "The idea that introns can exhibit presence/absence polymorphisms within a species is quite new and very few reports exist in the literature up until now," says Torriani.
The first reports of intron presence-absence polymorphisms include one gene found in the fruit fly Drosophila and a handful of genes in the water flea Daphnia. In their paper, which has just appeared in Current Biology, the group led by Professor McDonald added three new species that showed a multitude of intron polymorphisms.
Younger species in transition
In their work, the researchers compared not only genes from different individuals of M. graminicola, but also the same genes in other closely related fungal species. In some cases the evolutionarily older species had no intron in a gene, while the younger species M. graminicola was in a transitional stage where some individuals carried an intron while it was absent in others. "It is these rare transitional stages that will allow us to understand the evolutionary processes that lead to intron gains and losses in genomes," concludes co-author Daniel Croll. "Once the intron is present in every individual, it is fixed in the gene and we don't know h
|Contact: Bruce McDonald|
ETH Zurich/Swiss Federal Institute of Technology