RT Journal
A1 Cho, Soochin
A1 Jin, Suk-Won
A1 Cohen, Adam
A1 Ellis, Ronald E.
T1 A Phylogeny of Caenorhabditis Reveals Frequent Loss of Introns During Nematode Evolution
JF Genome Research 
JO Genome Research 
YR 2004 
FD July 01 
VO 14 
IS 7 
SP 1207 
OP 1220 
DO 10.1101/gr.2639304 
UL http://genome.cshlp.org/content/14/7/1207.abstract 
AB Since introns were discovered 26 years ago, people have wondered how changes in intron/exon structure occur, and what role these changes play in evolution. To answer these questions, we have begun studying gene structure in nematodes related to Caenorhabditis elegans. As a first step, we cloned a set of five genes from six different Caenorhabditis species, and used their amino acid sequences to construct the first detailed phylogeny of this genus. Our data indicate that nematode introns are lost at a very high rate during evolution, almost 400-fold higher than in mammals. These losses do not occur randomly, but instead, favor some introns and do not affect others. In contrast, intron gains are far less common than losses in these genes. On the basis of the sequences at each intron site, we suggest that several distinct mechanisms can cause introns to be lost. The small size of C. elegans introns should increase the rate at which each of these types of loss can occur, and might account for the dramatic difference in loss rate between nematodes and mammals.