title: Retroduplication and loss of parental genes is a mechanism for the generation of intronless genes in Ciona intestinalis and Ciona savignyi.
abstract: Tunicates, the sister clade of vertebrates, have miniature genomes and numerous intronless genes compared to other animals. It is still unclear how the tunicates acquired such a large number of intronless genes. Here, we analyzed sequences and intron-exon organizations of homologous genes from two closely related tunicates, Ciona intestinalis and Ciona savignyi. We found seven cases in which ancestral introns of a gene were completely lost in a species after their divergence. In four cases, both the intronless copy and the intron-containing copy were present in the genome, indicating that the intronless copy was generated by retroduplication. In the other three cases, the intron-containing copy was absent, implying it was lost after retroduplication. This result suggests that retroduplication and loss of parental genes is a major mechanism for the accumulation of intronless genes in tunicates.
authors.affiliation: Department of Life Science, Research Center for Biomolecules and Biosystems, Chung-Ang University, Seoul, 156-756, South Korea.
authors.forename: Dong Seon
authors.initials: DS
authors.lastname: Kim
authors.forename: Yao
authors.initials: Y
authors.lastname: Wang
authors.forename: Hye Ji
authors.initials: HJ
authors.lastname: Oh
authors.forename: Dongjin
authors.initials: D
authors.lastname: Choi
authors.forename: Kangseok
authors.initials: K
authors.lastname: Lee
authors.forename: Yoonsoo
authors.initials: Y
authors.lastname: Hahn
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002938:Ciona intestinalis / Q000235:genetics*; D019143:Evolution, Molecular; D020440:Gene Duplication; D007438:Introns; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D014561:Urochordata / Q000145:classification* / Q000235:genetics*