title: Environmental genomics: a tale of two fishes.
abstract: The influence of the environment on two congeneric fishes, Gillichthys mirabilis and Gillichthys seta, that live in the Gulf of California at temperatures of 10-25 degrees C, and up to 42-44 degrees C, respectively, was addressed by analyzing their genomes. Compared with G. mirabilis, G. seta showed some striking features. Substitution rates in the mitochondrial genes were found to be extremely fast, in fact faster than in noncoding control regions (D-loops), from which a divergence time of less than 0.66-0.75 Mya could be estimated. In the nuclear genome, 1) both AT --> GC/GC --> AT and transversion: transition ratios in coding sequences (CDSs) were relatively high; moreover, the ratios of nonsynonymous/synonymous changes (Ka/Ks) suggested that some genes were under positive selection; 2) DNA methylation showed a very significant decrease; and 3) a GC-rich minisatellite underwent a 4-fold amplification in the gene-rich regions. All these observations clearly indicate that the environment (temperature and the accompanying hypoxia) can rapidly mold the nuclear as well as the mitochondrial genome. The stabilization of gene-rich regions by the amplification of the GC-rich minisatellite and by the GC increase in nuclear CDSs is of special interest because it provides a model for the formation of the GC-rich and gene-rich isochores of the genomes of mammals and birds.
authors.affiliation: Laboratory of Molecular Evolution, Stazione Zoologica Anton Dohrn, Villa Comunale, Napoli, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Bucciarelli
authors.forename: Miriam
authors.initials: M
authors.lastname: Di Filippo
authors.forename: Domenico
authors.initials: D
authors.lastname: Costagliola
authors.forename: Fernando
authors.initials: F
authors.lastname: Alvarez-Valin
authors.forename: Giacomo
authors.initials: G
authors.lastname: Bernardi
authors.forename: Giorgio
authors.initials: G
authors.lastname: Bernardi
mesh_terms: D000818:Animals; D001482:Base Composition; D055028:Comparative Genomic Hybridization; D019175:DNA Methylation / Q000235:genetics; D004777:Environment; D019143:Evolution, Molecular; D029941:Fish Proteins / Q000235:genetics; D016678:Genome; D054629:Genome, Mitochondrial; D018598:Minisatellite Repeats / Q000235:genetics; D010100:Oxygen; D010473:Perciformes / Q000235:genetics*; D017354:Point Mutation; D013696:Temperature; D014461:Ultracentrifugation
chemical_list: D029941:Fish Proteins; D010100:Oxygen