Seventy new microsatellites for the pied flycatcher, Ficedula hypoleuca and amplification in other passerine birds

The pied flycatcher (Ficedula hypoleuca) is a small migratory passerine bird commonly distributed across Europe which has been the focus of considerable ecological and evolutionary research. Here, we present details of 70 microsatellite markers for the species adding to the six which are currently available. Sixty-six markers were also polymorphic in the closely related collared flycatcher (Ficedula albicollis), while 54 were polymorphic in another related passerine, the bluethroat (Luscinia svecica), and 12 were polymorphic in the more distantly related Siberian jay (Perisoreus infaustus).

Transcription and redox enzyme activities: comparison of equilibrium and disequilibrium levels in the three-spined stickleback

Evolutionary and acclimatory responses require functional variability, but in contrast with mRNA and protein abundance data, most physiological measurements cannot be obtained in a high-throughput manner. Consequently, one must either rely on high-throughput transcriptomic or proteomic data with only predicted functional information, or accept the limitation that most physiological measurements can give fewer data than those provided by transcriptomics or proteomics. We evaluated how transcriptional and redox enzyme activity data agreed with regard to population differentiation (i.e. a system in steady state in which any time lag between transcription, translation and post-translational effects would be irrelevant) and in response to an acute 6°C increase in temperature (i.e. a disequilibrium state wherein translation could not have caught up with transcription) in the three-spined stickleback (Gasterosteus aculeatus). Transcriptional and enzyme activity data corresponded well with regard to population differentiation, but less so with regard to acute temperature increase. The data thus suggest that transcriptional and functional measurements can lead to similar conclusions when a biological system is in a steady state. The responses to acute changes must, as has been demonstrated earlier, be based on changes in cellular conditions or properties of existing proteins without significant de novo synthesis of new gene products.

Responses of threespine stickleback (Gasterosteus aculeatus, L) transcriptome to hypoxia

Hypoxia is a naturally occurring phenomenon in aquatic systems. Its occurrence is potentiated by eutrophication caused by human actions and it may be made even more severe as a result of increasing temperatures due to climate change. Threespine stickleback (Gasterosteus aculeatus) has previously been used by ecologists and evolutionary biologists, but has great potential also for physiological studies. We subjected threespine sticklebacks to hypoxia (air saturation 24-28%) or normoxia for 3 and 48 h. To study changes in the transcriptome, microarray determinations were carried out for the 48 h treatments and complementary real-time quantitative PCR was run on selected transcripts at both time points. The microarray results suggest downregulation of genes encoding proteins with functions typically inhibited by hypoxia, i.e., cell proliferation, DNA replication and repair, and protein degradation, and upregulation of transcripts with products having oxygenase and oxidase activities including two 2-oxoglutarate-deoxygenases. These transcripts encode for JmjC domain containing proteins JMJD6 and JMJD2C. JMJD6 transcription has not earlier been characterized to change in hypoxia. Cyp1A2 mRNA was also increased in the microarray and the upregulation could be confirmed on protein level by measuring ethoxyresorufin-O-deethlyase (EROD)-activity.

Strong gene flow and lack of stable population structure in the face of rapid adaptation to local temperature in a spring-spawning salmonid, the European grayling (Thymallus thymallus)

Gene flow has the potential to both constrain and facilitate adaptation to local environmental conditions. The early stages of population divergence can be unstable because of fluctuating levels of gene flow. Investigating temporal variation in gene flow during the initial stages of population divergence can therefore provide insights to the role of gene flow in adaptive evolution. Since the recent colonization of Lake Lesjaskogsvatnet in Norway by European grayling (Thymallus thymallus), local populations have been established in over 20 tributaries. Multiple founder events appear to have resulted in reduced neutral variation. Nevertheless, there is evidence for local adaptation in early life-history traits to different temperature regimes. In this study, microsatellite data from almost a decade of sampling were assessed to infer population structuring and its temporal stability. Several alternative analyses indicated that spatial variation explained 2-3 times more of the divergence in the system than temporal variation. Over all samples and years, there was a significant correlation between genetic and geographic distance. However, decomposed pairwise regression analysis revealed differing patterns of genetic structure among local populations and indicated that migration outweighs genetic drift in the majority of populations. In addition, isolation by distance was observable in only three of the six years, and signals of population bottlenecks were observed in the majority of samples. Combined, the results suggest that habitat-specific adaptation in this system has preceded the development of consistent population substructuring in the face of high levels of gene flow from divergent environments.

Endocrine effects of growth hormone overexpression in transgenic coho salmon

Non-transgenic (wild-type) coho salmon (Oncorhynchus kisutch), growth hormone (GH) transgenic salmon (with highly elevated growth rates), and GH transgenic salmon pair fed a non-transgenic ration level (and thus growing at the non-transgenic rate) were examined for plasma hormone concentrations, and liver, muscle, hypothalamus, telencephalon, and pituitary mRNA levels. GH transgenic salmon exhibited increased plasma GH levels, and enhanced liver, muscle and hypothalamic GH mRNA levels. Insulin-like growth factor-I (IGF-I) in plasma, and growth hormone receptor (GHR) and IGF-I mRNA levels in liver and muscle, were higher in fully fed transgenic than non-transgenic fish. GHR mRNA levels in transgenic fish were unaffected by ration-restriction, whereas plasma GH was increased and plasma IGF-I and liver IGF-I mRNA were decreased to wild-type levels. These data reveal that strong nutritional modulation of IGF-I production remains even in the presence of constitutive ectopic GH expression in these transgenic fish. Liver GHR membrane protein levels were not different from controls, whereas, in muscle, GHR levels were elevated approximately 5-fold in transgenic fish. Paracrine stimulation of IGF-I by ectopic GH production in non-pituitary tissues is suggested by increased basal cartilage sulphation observed in the transgenic salmon. Levels of mRNA for growth hormone-releasing hormone (GHRH) and cholecystokinin (CCK) did not differ between groups. Despite its role in appetite stimulation, neuropeptide Y (NPY) mRNA was not found to be elevated in transgenic groups.

The pro-opiomelanocortin genes in rainbow trout (Oncorhynchus mykiss): duplications, splice variants, and differential expression

Pro-opiomelanocortin (POMC) is a precursor for several important peptide hormones involved in a variety of functions ranging from stress response to energy homeostasis. In mammals and fish, the POMC-derived peptide alpha-melanocyte stimulating hormone (MSH) is known to be involved in appetite suppression through its interaction with melanocortin-4 receptors. The details of energy homeostasis in fishes are beginning to be elucidated and many of the genes involved in mammalian neuroendocrine signaling pathways are being discovered in fish. In salmonid fishes such as the rainbow trout, genome duplication adds another degree of complexity when trying to compare gene function and homology with other vertebrates. This is true of the POMC gene. Two copies of the POMC gene were previously identified, A and B, presumably resulting from the salmonid duplication. However, while investigating POMC involvement in the feeding response of rainbow trout, a second copy of POMC-A was discovered which is more likely the result of the salmonid duplication and suggests that POMC-B is a duplicate resulting from the earlier teleost duplication prior to tetrapod divergence. The duplicated POMC-A had five deleted amino acids, five inserted amino acids, and 39 amino acid differences from the published POMC-A. In addition to the duplicate POMC-A, a splice variant of the published POMC-A sequence was also identified. Quantitative real-time PCR assays were developed for the different POMC transcripts, and expression was examined in a variety of tissues. Expression of POMC transcripts was highest in the pituitary for all POMC genes, but varied among other tissues for POMC-A1, POMC-A2, POMC-A2s, and POMC-B. POMC-A1 was the only transcript to respond significantly to food deprivation.

The candidate gene, Clock, localizes to a strong spawning time quantitative trait locus region in rainbow trout

We applied a candidate gene mapping approach to an existing quantitative trait loci (QTL) data set for spawning date in rainbow trout (Oncorynchus mykiss) to ascertain whether these genes could potentially account for any observed QTL effects. Several genes were chosen for their known or suspected roles in reproduction, circadian, or circannual timing, including salmon-type gonadotropin-releasing hormone 3A and 3B (GnRH3A and GnRH3B), Clock, Period1, and arylalkylamine N-acetlytransferase-1 and -2 (AANAT-1 and AANAT-2). Genes were sequenced, and polymorphisms were identified in parents of two rainbow trout mapping families, one of which was used previously to detect spawn timing QTL. Interval mapping was used to identify associations between genetic markers and spawning date effects. Using a genetic map that was updated with 574 genetic markers (775 total), we found evidence for 11 significant or suggestive QTL regions. Most QTL were only localized within one of the parents; however, a strong QTL region was identified in both female and male parents on linkage group RT-8 that explained 20% and 50% of trait variance, respectively. The Clock gene mapped to this region. Period1 mapped to a region in the female parent associated with a marginal effect (P = .056) on spawn timing. Other candidate genes were not associated with significant QTL effects.

Comparison of GNRH3 genes across salmonid genera

Genomic sequences of gonadotropin-releasing hormone genes were amplified and examined for sequence divergence among members of three different genera of the subfamily Salmoninae: rainbow trout (Oncorhynchus mykiss), Atlantic salmon (Salmo salar), and Arctic charr (Salvelinus alpinus). Sequences of GNRH3A and GNRH3B (formerly known as sGnRH1 and sGnRH2) were 97-99% similar in coding regions and 94-98% similar in non-coding regions among genera, but comparisons within species between GNRH3A and GNRH3B were only 90-92% similar in coding regions and 83-89% similar in non-coding regions. Polymorphisms in the parents of mapping families for each species allowed for linkage mapping of the GNRH3B gene in all three species and the GNRH3A gene in rainbow trout. GNRH3B maps to linkage group 6 in rainbow trout, linkage group 16 in Atlantic salmon and linkage group 25 in Arctic charr. GNRH3A mapped to linkage group 30 in rainbow trout.