RESUMEN
High-throughput RNA sequencing is a powerful tool that allows us to perform gene prediction and analyze tissue-specific overexpression of genes, but also at species level comparisons can be performed, although in a more restricted manner. In the present study complete liver transcriptomes of five tropical bat species were De novo assembled and annotated. Highly expressed genes in the five species were involved in glycolysis and lipid metabolism pathways. Cross-species differential expression analysis was conducted using single copy orthologues shared across the five species. Between 22 and 29 orthologs were upregulated for each species. We detected upregulated expression in Artibeus jamaicensis genes related to fructose metabolism pathway. Such findings can be correlated with A. jamaicensis dietary habits, as it was the unique frugivorous species included. This is the first report of transcriptome assembly by RNA-seq in these species, except for A. jamaicensis and as far as our knowledge is the first cross-species comparisons of transcriptomes and gene expression in tropical bats.
Asunto(s)
Quirópteros/clasificación , Quirópteros/genética , Anotación de Secuencia Molecular , Transcriptoma , Animales , Expresión Génica , Perfilación de la Expresión Génica , Glucólisis/genética , Secuenciación de Nucleótidos de Alto Rendimiento , Metabolismo de los Lípidos/genética , Hígado , Filogenia , RNA-Seq , Análisis de Secuencia de ARNRESUMEN
The genes of the Major Histocompatibility Complex (MHC) play an important role in the vertebrate immune response and are among the most polymorphic genes known in vertebrates. In some marine mammals, MHC genes have been shown to be characterized by low levels of polymorphism compared to terrestrial taxa; this reduction in variation is often explained as a result of lower pathogen pressures in marine habitats. To determine if this same reduction in variation applies to the migratory population of blue whales (Balaenoptera musculus) that occurs in the Gulf of California, we genotyped a 172 bp fragment of exon 2 of the MHC Class II DQB locus for 80 members of this population. Twenty-two putatively functional DQB allotypes were identified, all of which were homologous with DQB sequences from other cetacean species. Up to 5 putative alleles per individual were identified, suggesting that gene duplication has occurred at this locus. Rates of non-synonymous to synonymous substitutions (ω) and maximum likelihood analyses of models of nucleotide variation provided potential evidence of ongoing positive selection at this exon. Phylogenetic analyses of DQB alleles from B. musculus and 16 other species of cetaceans revealed trans-specific conservation of MHC variants, suggesting that selection has acted on this locus over prolonged periods of time. Collectively our findings reveal that immunogenic variation in blue whales is comparable to that in terrestrial mammals, thereby providing no evidence that marine taxa are subject to reduced pathogen-induced selective pressures.