Ascidian and Amphioxus Adh Genes Correlate Functional and Molecular Features of the ADH Family Expansion During Vertebrate Evolution |
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Authors: | Cristian Cañestro Ricard Albalat Lars Hjelmqvist Laura Godoy Hans Jörnvall Roser Gonzàlez-Duarte |
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Institution: | (1) Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, Av. Diagonal 645, E-08028 Barcelona, Spain, ES;(2) Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-17177 Stockholm, Sweden, SE |
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Abstract: | The alcohol dehydrogenase (ADH) family has evolved into at least eight ADH classes during vertebrate evolution. We have characterized
three prevertebrate forms of the parent enzyme of this family, including one from an urochordate (Ciona intestinalis) and two from cephalochordates (Branchiostoma floridae and Branchiostoma lanceolatum). An evolutionary analysis of the family was performed gathering data from protein and gene structures, exon–intron distribution,
and functional features through chordate lines. Our data strongly support that the ADH family expansion occurred 500 million
years ago, after the cephalochordate/vertebrate split, probably in the gnathostome subphylum line of the vertebrates. Evolutionary
rates differ between the ancestral, ADH3 (glutathione-dependent formaldehyde dehydrogenase), and the emerging forms, including
the classical alcohol dehydrogenase, ADH1, which has an evolutionary rate 3.6-fold that of the ADH3 form. Phylogenetic analysis
and chromosomal mapping of the vertebrate Adh gene cluster suggest that family expansion took place by tandem duplications, probably concurrent with the extensive isoform
burst observed before the fish/tetrapode split, rather than through the large-scale genome duplications also postulated in
early vertebrate evolution. The absence of multifunctionality in lower chordate ADHs and the structures compared argue in
favor of the acquisition of new functions in vertebrate ADH classes. Finally, comparison between B. floridae and B. lanceolatum Adhs provides the first estimate for a cephalochordate speciation, 190 million years ago, probably concomitant with the beginning
of the drifting of major land masses from the Pangea.
Received: 10 April 2001 / Accepted: 23 May 2001 |
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Keywords: | : Alcohol dehydrogenase — Evolutionary rate — Gene duplication — Vertebrate genome evolution |
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