Late Changes in Spliceosomal Introns Define Clades in Vertebrate Evolution

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 96; no. 18; pp. 10267 - 10271
• Main Authors: Venkatesh, Byrappa, Ning, Yana, Brenner, Sydney
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 31.08.1999; National Acad Sciences; National Academy of Sciences; The National Academy of Sciences
• Subjects: Amino Acid Sequence; Animals; Base Sequence; Biological evolution; Biological Sciences; Cloning, Molecular; Codons; Dystrophin - genetics; Evolution; Evolution, Molecular; Exons; Exons - genetics; Fish; Fishes - classification; Fishes - genetics; Fugu; Genetic Markers; Genetics; Growth Hormone - genetics; Growth hormones; Introns; Introns - genetics; Molecular Sequence Data; Phylogenetics; Phylogeny; Polymerase Chain Reaction; Polypterus; Rhodopsin - genetics; Sequencing; Spliceosomes - genetics; Vertebrates - classification; Vertebrates - genetics
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.96.18.10267

The evolutionary origin of spliceosomal introns has been the subject of much controversy. Introns are proposed to have been both lost and gained during evolution. If the gain or loss of introns are unique events in evolution, they can serve as markers for phylogenetic analysis. We have made an extensive survey of the phylogenetic distribution of seven spliceosomal introns that are present in Fugu genes, but not in their mammalian homologues; we show that these introns were acquired by actinopterygian (ray-finned) fishes at various stages of evolution. We have also investigated the intron pattern of the rhodopsin gene in fishes, and show that the four introns found in the ancestral chordate rhodopsin gene were simultaneously lost in a common ancestor of ray-finned fishes. These changes in introns serve as excellent markers for phylogenetic analysis because they reliably define clades. Our intron-based cladogram establishes the difficult-to-ascertain phylogenetic relationships of some ray-finned fishes. For example, it shows that bichirs (Polypterus) are the sister group of all other extant ray-finned fishes.