Worms reveal intron insights
Team finds "newborn" introns by comparing C. elegans and C.
briggsae genomes
By Nicole Johnston

Irish researchers have discovered 122 novel introns that appeared in the
genomes of Caenorhabditis elegans and Caenorhabditis briggsae since the two
species diverged 80 to 120 million years ago, shedding light on how new
introns arise and are subsequently spread among genes.

The genomes of both worms contain roughly 100,000 introns, of which more
than 6000 are unique to one species or the other. Kenneth Wolfe and Avril
Coghlan identified 81 new introns in C. elegans and 41 new introns in C.
briggsae. Of these, 13 are found in genes implicated in premRNA processing,
the authors report in the June 28 PNAS early online edition.

"We used BLAST [Basic Local Alignment Search Tool] to identify orthologous
genes across all the species (animal and nematode), and by comparison of all
genes, we were able to find intron sites present in one of the nematodes,
but absent in all other species," Wolfe, from Trinity College Dublin, told
The Scientist. "We therefore inferred that these gained introns must be less
than 100 million years old."

Their results represent two major findings, said John Logsdon, an
evolutionary biologist at the University of Iowa. One of these is the
finding that introns are changing a lot, both in terms of gain and loss.
"The more incredibly novel part, is that this is some of the first evidence
of how one intron can give rise to another," he said. Even more significant
is the fact that the authors used actual sequence data to infer the process
by which introns were gained, rather than relying on phylogenetic arguments,
the conventional approach to studying intron evolution, he added.

Read the rest at TheScientist.com
http://www.biomedcentral.com/news/20040629/01

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