RESUMEN
BACKGROUND: Once highly abundant, the European eel (Anguilla anguilla L.; Anguillidae; Teleostei) is considered to be critically endangered and on the verge of extinction, as the stock has declined by 90-99% since the 1980s. Yet, the species is poorly characterized at molecular level with little sequence information available in public databases. RESULTS: The first European eel transcriptome was obtained by 454 FLX Titanium sequencing of a normalized cDNA library, produced from a pool of 18 glass eels (juveniles) from the French Atlantic coast and two sites in the Mediterranean coast. Over 310,000 reads were assembled in a total of 19,631 transcribed contigs, with an average length of 531 nucleotides. Overall 36% of the contigs were annotated to known protein/nucleotide sequences and 35 putative miRNA identified. CONCLUSIONS: This study represents the first transcriptome analysis for a critically endangered species. EeelBase, a dedicated database of annotated transcriptome sequences of the European eel is freely available at http://compgen.bio.unipd.it/eeelbase. Considering the multiple factors potentially involved in the decline of the European eel, including anthropogenic factors such as pollution and human-introduced diseases, our results will provide a rich source of data to discover and identify new genes, characterize gene expression, as well as for identification of genetic markers scattered across the genome to be used in various applications.
Asunto(s)
Anguilla/genética , Bases de Datos de Ácidos Nucleicos , Especies en Peligro de Extinción , Perfilación de la Expresión Génica , Anotación de Secuencia Molecular , Análisis de Secuencia de ADN/métodos , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Mapeo Contig , Bases de Datos de Proteínas , Europa (Continente) , Proteínas de Peces/química , Proteínas de Peces/genética , Genoma/genética , Humanos , MicroARNs/genética , Reproducibilidad de los Resultados , Homología de Secuencia de Ácido Nucleico , Smegmamorpha/genética , Especificidad de la Especie , Pez Cebra/genéticaRESUMEN
BACKGROUND: Winter migration of immature brown trout (Salmo trutta) into freshwater rivers has been hypothesized to result from physiologically stressful combinations of high salinity and low temperature in the sea. RESULTS: We sampled brown trout from two Danish populations entering different saline conditions and quantified expression of the hsp70 and Na/K-ATPases alpha 1b genes following acclimation to freshwater and full-strength seawater at 2 degrees C and 10 degrees C. An interaction effect of low temperature and high salinity on expression of both hsp70 and Na/K-ATPase alpha 1b was found in trout from the river entering high saline conditions, while a temperature independent up-regulation of both genes in full-strength seawater was found for trout entering marine conditions with lower salinities. CONCLUSION: Overall our results support the hypothesis that physiologically stressful conditions in the sea drive sea-run brown trout into freshwater rivers in winter. However, our results also demonstrate intra-specific differences in expression of important stress and osmoregulative genes most likely reflecting adaptive differences between trout populations on a regional scale, thus strongly suggesting local adaptations driven by the local marine environment.
Asunto(s)
Aclimatación , Migración Animal , Salinidad , Trucha/genética , Animales , Agua Dulce , Variación Genética , Branquias/enzimología , Proteínas HSP70 de Choque Térmico/genética , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Agua de Mar , ATPasa Intercambiadora de Sodio-Potasio/metabolismoRESUMEN
Knockdown resistance to high temperature (KRHT) is a thermal adaptation trait in Drosophila melanogaster. Here we used quantitative real-time PCR (qRT-PCR) to test for possible associations between KRHT and the expression of candidate genes within quantitative trait loci (QTL) in eight recombinant inbred lines (RIL). hsp60 and hsc70-3 map within an X-linked QTL, while CG10383, catsup, ddc, trap1, and cyp6a13 are linked in a KRHT-QTL on chromosome 2. hsc70-3 expression increased by heat-hardening. Principal Components analysis revealed that catsup, ddc and trap1 were either co-expressed or combined in their expression levels. This composite expression variable (e-PC1) was positively associated to KRHT in non-hardened RIL. In heat-hardened flies, hsp60 was negatively related to hsc70-3 on e-PC2, with effects on KRHT. These results are consistent with the notion that QTL can be shaped by expression variation in combined candidate loci. We found composite variables of gene expression (e-PCs) that best correlated to KRHT. Network effects with other untested linked loci are apparent because, in spite of their associations with KRHT phenotypes, e-PCs were sometimes uncorrelated with their QTL genotype.
Asunto(s)
Drosophila melanogaster/genética , Regulación de la Expresión Génica , Sitios de Carácter Cuantitativo , Animales , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/química , Drosophila melanogaster/metabolismo , Femenino , Calor , MasculinoRESUMEN
Population structure was previously believed to be very limited or absent in classical marine fishes, but recently, evidence of weakly differentiated local populations has been accumulating using noncoding microsatellite markers. However, the evolutionary significance of such minute genetic differences remains unknown. Therefore, in order to elucidate the relationship between genetic markers and adaptive divergence among populations of marine fishes, we combined cDNA microarray and microsatellite analysis in European flounders (Platichthys flesus). We demonstrate that despite extremely low levels of neutral genetic divergence, a high number of genes were significantly differentially expressed between North Sea and Baltic Sea flounders maintained in a long-term reciprocal transplantation experiment mimicking natural salinities. Several of the differentially regulated genes could be directly linked to fitness traits. These findings demonstrate that flounders, despite little neutral genetic divergence between populations, are differently adapted to local environmental conditions and imply that adaptation in gene expression could be common in other marine organisms with similar low levels of population subdivision.