1,721,187 research outputs found
Antarctic fish hemoglobins: evidence of adaptive evolution at subzero temperature
No full textNotothenioids represent a large group of marine teleosts that are mostly endemic to the Antarctic Ocean. In this environment, the low metabolic demand and the high oxygen concentration reduce the need for hemoglobin(s) [Hb(s)]. The extreme condition is represented by the icefish (Channichthyidae, Notothenioidei), the only vertebrates that lack Hb. We obtained the nucleotide sequence coding for the beta-globin chain of the single major Hb form in six red-blooded notothenioids. These included Gymnodraco acuticeps, one of the closest species to the Hb-less icefish, which is also the only known fish having a single Hb without Bohr effect. This species shows a higher rate of nonsynonymous substitutions (K-A), in contrast with the homogeneity of synonymous substitution (K-S) rates, and K-A/K-S ratios significantly greater than one in the majority of comparisons. These results are suggestive of positive selection, diversifying the single major Hb toward specialized functions. A single Hb that is free to diversify means that its role in routine oxygen transport can be reduced in the presence of a combination of physiological, ecological, and environmental factors. Although a reduced "routine" function for Hb, as is apparent in G. acuticeps, might, indeed, evoke the lack of Hb in icefish, evidence of diversifying selection reported here is at variance with the hypothesis of a simple trend from a single Hb toward the Hb-less condition
Inherited disease in dogs: molecular genetics applied to diagnosis
No full textThe recent progresses of molecular genetics and biotechnology allowed to significantly advance in the field of biomedical sciences. These extraordinary progresses also regarded species of veterinary interest such as dog, the genome of which was completely sequenced. More than 350 dog-breed gene pools combined to new powerful technologies represent a unique opportunity to investigate the molecular basis of inherited canine disorders as well as to develop appropriate test for quick and accurate molecular diagnosis
Strategies for microsatellite isolation: a review
No full textIn the last few years microsatellites have become one of the most popular molecular markers used with applications in many different fields. High polymorphism and the relative ease of scoring represent the two major features that make microsatellites of large interest for many genetic studies. The major drawback of microsatellites is that they need to be isolated de novo from species that are being examined for the first time. The aim of the present paper is to review the various methods of microsatellite isolation described in the literature with the purpose of providing useful guidelines in making appropriate choices among the large number of currently available options. In addition, we propose a fast and easy protocol which is a combination of different published methods
Molecular zoogeography of Antarctic euphausiids and notothenioids: from species phylogenies to intraspecific patterns of genetic variation
No full textPublished and unpublished data are used to investigate possible mechanisms of species diversification in two key soups of Antarctic organisms. the Notothenioidei and the Euphausiidae. Species distributions are mapped onto molecular phylogenies, and this evidence is interpreted in light of the various ecological and historical factors which characterize the Southern Ocean. The joint effect of diverse agents (vicariance, "jump" dispersal) appears to be determinant in several cases for species divergence. A review of results from population genetics studies, together with new molecular evidence, confirm the importance of physical barriers (oceanographic fronts) in reducing migration, thereby promoting speciation, at least in notothenioids
Krill evolution and the Antarctic ocean currents: Evidence of vicariant speciation as inferred by molecular data
No full textThe phylogenetic relationships of the Antarctic krill Euphausia superba, the key species in the Antarctic food web, and other Antarctic and sub-Antarctic euphausiids have been investigated using the 16S ribosomal mitochondrial gene. The phylogenetic reconstructions indicated that the Antarctic species form a monophyletic clade separated by the non-Antarctic species. The results revealed a large genetic divergence between the Antarctic (E. superba and E. crystallorophias) and sub-Antarctic species (E. vallentini). The time of separation between these species, estimated from the molecular data, is around 20 million years ago, which is comparable with the geological time of the formation of a circum-Antarctic water circulation and the Antarctic Polar Frontal Zone. The euphausiid molecular phylogeny therefore represents evidence for vicariant speciation
Isolating genes of potential interest for aquaculture: some caveat from a comparative study
No full textMitochondrial phylogeny of notothenioids: A molecular approach to antarctic fish evolution and biogeography
No full textAntarctic waters represent a unique marine environment delimited by an oceanographic barrier, the Polar Front Zone, and characterized by constant subzero temperatures and presence of sea ice. A group of teleost fish, the Notothenioidei, have adapted to these challenging environmental conditions, undergoing a remarkable diversification. In the present study a total of 798 base pairs, generated from partial sequencing of 16S and 12S mitochondrial ribosomal RNA genes, were examined in 33 notothenioid species representative of all families included in the suborder Notothenioidei. Phylogenetic trees, reconstructed on the basis of sequence data by different methods, indicate that traditional hypotheses on notothenioid systematics and biogeography might be in need of reexamination. Molecular evidence suggests that vicariant speciation could be invoked to explain the early divergence of Eleginops maclovinus, a species previously included in the family Nototheniidae, which is now proposed as the closest sister group to all the rest of notothenioids apart from bovichtids. On the other hand, repeated, independent dispersal through the Polar Front is proposed for the divergence of other subantarctic notothenioid species. Likewise, multiple, independent transitions from benthic to pelagic habit are inferred from molecular data, at variance with the more conservative hypothesis based on cladograms reconstructed from morphological data
Isolation and characterization of a FTZ-F1-homolog in the gilthead sea bream, Sparus aurata L
No full textMitochondrial DNA sequence variation in the European sea bass, Dicentrarchus labrax L. (Serranidae): evidence of differential haplotype distribution in natural and farmed populations
No full textPCR and direct sequencing of 300 to 377-bp fragments of the cytochrome b mitochondrial gene were carried out in 40 specimens of European sea bass, Dicentrarchus labrax L., collected at different sites in the Mediterranean basin and representing wild and farmed populations. Sequence analysis revealed 6 transitional changes, which generated 5 different haplotypes (A-E). Only one mutation was nonsynonymous because it occurred in the first position of a codon leading to the replacement of valine by isoleucine. The genotypic distribution revealed that haplotype B was not present in the farm samples, whereas its frequency in the wild samples exceeded 30%. In contrast, haplotypes D and E were found in farmed populations but not in the wild populations. The comparison among wild populations showed a nonhomogeneous distribution of the two most frequent haplotypes, A and B
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