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Bird beaks are textbook examples of ecological adaptation to diet, but their shapes are also controlled by genetic and developmental histories. To test the effects of these factors on the avian craniofacial skeleton, we conducted morphometric analyses on raptors, a polyphyletic group at the base of the landbird radiation. Despite common perception, we find that the beak is not an independently targeted module for selection. Instead, the beak and skull are highly integrated structures strongly regulated by size, with axes of shape change linked to the actions of recently identified regulatory genes. Together, size and integration account for almost 80% of the shape variation seen between different species to the exclusion of morphological dietary adaptation. Instead, birds of prey use size as a mechanism to modify their feeding ecology. The extent to which shape variation is confined to a few major axes may provide an advantage in that it facilitates rapid morphological evolution via changes in body size, but may also make raptors especially vulnerable when selection pressures act against these axes. The phylogenetic position of raptors suggests that this constraint is prevalent in all landbirds and that breaking the developmental correspondence between beak and braincase may be the key novelty in classic passerine adaptive radiations.

In mammals, testis development is triggered by the expression of the sex-determining Y-chromosome gene SRY to commit the Sertoli cell (SC) fate at gonadal sex determination in the fetus. Several genes have been identified to be required to promote the testis pathway following SRY activation (i.e., SRY box 9 (SOX9)) in an embryo; however, it largely remains unknown about the genes and the mechanisms involved in stabilizing the testis pathway after birth and throughout adulthood. Herein, we report postnatal males with SC-specific deletion of Raptor demonstrated the absence of SC unique identity and adversely acquired granulosa cell-like characteristics, along with loss of tubular architecture and scattered distribution of SCs and germ cells. Subsequent genome-wide analysis by RNA sequencing revealed a profound decrease in the transcripts of testis genes (i.e., Sox9, Sox8, and anti-Mullerian hormone (Amh)) and, conversely, an increase in ovary genes (i.e., LIM/Homeobox gene 9 (Lhx9), Forkhead box L2 (Foxl2) and Follistatin (Fst)); these changes were further confirmed by immunofluorescence and quantitative reverse-transcription polymerase chain reaction. Importantly, co-immunofluorescence demonstrated that Raptor deficiency induced SCs dedifferentiation into a progenitor state; the Raptor-mutant gonads showed some ovarian somatic cell features, accompanied by enhanced female steroidogenesis and elevated estrogen levels, yet the zona pellucida 3 (ZP3)-positive terminally feminized oocytes were not observed. In vitro experiments with primary SCs suggested that Raptor is likely involved in the fibroblast growth factor 9 (FGF9)-induced formation of cell junctions among SCs. Our results established that Raptor is required to maintain SC identity, stabilize the male pathway, and promote testis development. Summary Sentence Raptor deletion induced Sertoli cells into an undifferentiated state and showed some ovarian somatic cell features. Graphical Abstract

Most species of migrating birds use a combination of innate vector-based orientation programs and social information to facilitate accurate navigation during their life. A number of various interspecies hybridisations have been reported in birds. The traits of parents are expressed in hybrids in typical ways which are either intermediate, combined or heterotic. Here, we analyse the different migration behaviours of medium-sized raptors, i.e., Red Kites Milvus milvus , Black Kites Milvus migrans , and their hybrids. We chose six well-established parameters to compare the behaviour of Kite hybrids with those of both parental species. When comparing 16 quantified behavioural characteristics between Red Kites and F1 hybrids and between Black Kites and F1 hybrids, significant differences were found in 10 characteristics between Red Kites and F1 hybrids but only one of the 16 characteristics between Black Kites and F1 hybrids. Hence, F1 hybrid individuals showed behaviour much more similar to Black Kites than Red Kites. It implies that the basis of the migratory behaviour of Kites is an innate program with the dominance of genetic determinants supplemented by the use of social learning from individuals of the parent species.

Background Birds of prey (raptors) are dominant apex predators in terrestrial communities, with hawks (Accipitriformes) and falcons (Falconiformes) hunting by day and owls (Strigiformes) hunting by night. Results Here, we report new genomes and transcriptomes for 20 species of birds, including 16 species of birds of prey, and high-quality reference genomes for the Eurasian eagle-owl ( Bubo bubo ), oriental scops owl ( Otus sunia ), eastern buzzard ( Buteo japonicus ), and common kestrel ( Falco tinnunculus ). Our extensive genomic analysis and comparisons with non-raptor genomes identify common molecular signatures that underpin anatomical structure and sensory, muscle, circulatory, and respiratory systems related to a predatory lifestyle. Compared with diurnal birds, owls exhibit striking adaptations to the nocturnal environment, including functional trade-offs in the sensory systems, such as loss of color vision genes and selection for enhancement of nocturnal vision and other sensory systems that are convergent with other nocturnal avian orders. Additionally, we find that a suite of genes associated with vision and circadian rhythm are differentially expressed in blood tissue between nocturnal and diurnal raptors, possibly indicating adaptive expression change during the transition to nocturnality. Conclusions Overall, raptor genomes show genomic signatures associated with the origin and maintenance of several specialized physiological and morphological features essential to be apex predators.

Background The behaviour of blood-sucking arthropods is a crucial determinant of blood protozoan distribution and hence of host-parasite coevolution, but it is very challenging to study in the wild. The molecular identification of parasite lineages in vectors can be a useful key to understand the behaviour and transmission patterns realised by these vectors. Methods In this study, we collected blackflies around nests of three raptor species in the upper forest canopy in central Europe and examined the presence of vertebrate DNA and haemosporidian parasites in them. We molecularly analysed 156 blackfly individuals, their vertebrate blood meals, and the haemosporidian parasite lineages they carried. Results We identified nine species of Simulium blackflies, largely belonging to the subgenera Nevermannia and Eusimulium . Only 1% of the collected specimens was visibly engorged, and only 4% contained remains of host DNA. However, in 29% of the blackflies Leucocytozoon lineages were identified, which is evidence of a previous blood meal on an avian host. Based on the known vertebrate hosts of the recorded Leucocytozoon lineages, we can infer that large and/or abundant birds, such as thrushes, crows, pigeons, birds of prey, owls and tits are the main targets of ornithophilic blackflies in the canopy. Blackfly species contained similar proportions of host group-specific parasite lineages and thus do not appear to be associated with particular host groups. Conclusions The Leucocytozoon clade infecting thrushes, crows, and pigeons present in most represented blackfly species suggests a lack of association between hosts and blackflies, which can increase the probability of host switches of blood parasites. However, the composition of the simuliid species differed between nests of common buzzards, goshawks and red kites. This segregation can be explained by coinciding habitat preferences between host and vector, and may lead to the fast speciation of Leucocytozoon parasites. Thus, subtle ecological preferences and lack of host preference of vectors in the canopy may enable both parasite diversification and host switches, and enforce a habitat-dependent evolution of avian malaria parasites and related haemosporidia.

Although most birds show karyotypes with diploid number (2n) around 80, with few macrochromosomes and many microchromosomes pairs, some groups, such as the Accipitriformes, are characterized by a large karyotypic reorganization, which resulted in complements with low diploid numbers, and a smaller number of microchromosomal pairs when compared to other birds. Among Accipitriformes, the Accipitridae family is the most diverse and includes, among other subfamilies, the subfamily Aquilinae, composed of medium to large sized species. The Black-Hawk-Eagle ( Spizaetus tyrannus -STY), found in South America, is a member of this subfamily. Available chromosome data for this species includes only conventional staining. Hence, in order to provide additional information on karyotype evolution process within this group, we performed comparative chromosome painting between S . tyrannus and Gallus gallus (GGA). Our results revealed that at least 29 fission-fusion events occurred in the STY karyotype, based on homology with GGA. Fissions occurred mainly in syntenic groups homologous to GGA1-GGA5. On the other hand, the majority of the microchromosomes were found fused to other chromosomal elements in STY, indicating these rearrangements played an important role in the reduction of the 2n to 68. Comparison with hybridization pattern of the Japanese-Mountain-Eagle ( Nisaetus nipalensis orientalis ), the only Aquilinae analyzed by comparative chromosome painting previously, did not reveal any synapomorphy that could represent a chromosome signature to this subfamily. Therefore, conclusions about karyotype evolution in Aquilinae require additional painting studies.

Background Studies of non-model species are important for understanding the molecular processes underpinning phenotypic variation under natural ecological conditions. The common buzzard ( Buteo buteo ; Aves: Accipitriformes) is a widespread and common Eurasian raptor with three distinct plumage morphs that differ in several fitness-related traits, including parasite infestation. To provide a genomic resource for plumage polymorphic birds in general and to search for candidate genes relating to fitness, we generated a transcriptome from a single dead buzzard specimen plus easily accessible, minimally invasive samples from live chicks. Results We not only de novo assembled a near-complete buzzard transcriptome, but also obtained a significant fraction of the transcriptome of its malaria-like parasite, Leucocytozoon buteonis . By identifying melanogenesis-related transcripts that are differentially expressed in light ventral and dark dorsal feathers, but which are also expressed in other regions of the body, we also identified a suite of candidate genes that could be associated with fitness differences among the morphs. These include several immune-related genes, providing a plausible link between melanisation and parasite load. qPCR analysis of a subset of these genes revealed significant differences between ventral and dorsal feathers and an additional effect of morph. Conclusion This new resource provides preliminary insights into genes that could be involved in fitness differences between the buzzard colour morphs, and should facilitate future studies of raptors and their malaria-like parasites.

During the last decade, the major histocompatibility complex (MHC) has received much attention in the fields of evolutionary and conservation biology because of its potential implications in many biological processes. New insights into the gene structure and evolution of MHC genes can be gained through study of additional lineages of birds not yet investigated at the genomic level. In this study, we characterized MHC class II B genes in five families of birds of prey (Accipitridae, Pandionidae, Strigidae, Tytonidae, and Falconidae). Using PCR approaches, we isolated genomic MHC sequences up to 1300 bp spanning exons 1 to 3 in 26 representatives of each raptor lineage, finding no stop codons or frameshift mutations in any coding region. A survey of diversity across the entirety of exon 2 in the lesser kestrel Falco naumanni reported 26 alleles in 21 individuals. Bayesian analysis revealed 21 positively selected amino acid sites, which suggests that the MHC genes described here are functional and probably expressed. Finally, through interlocus comparisons and phylogenetic analysis, we also discuss genetic evidence for concerted and transspecies evolution in the raptor MHC.

Background Genomic studies in non-domestic avian models, such as the California condor and white-throated sparrow, can lead to more comprehensive conservation plans and provide clues for understanding mechanisms affecting genetic variation, adaptation and evolution. Developing genomic tools and resources including genomic libraries and a genetic map of the California condor is a prerequisite for identification of candidate loci for a heritable embryonic lethal condition. The white-throated sparrow exhibits a stable genetic polymorphism (i.e. chromosomal rearrangements) associated with variation in morphology, physiology, and behavior (e.g., aggression, social behavior, sexual behavior, parental care). In this paper we outline the utility of these species as well as report on recent advances in the study of their genomes. Results Genotyping of the condor resource population at 17 microsatellite loci provided a better assessment of the current population's genetic variation. Specific New World vulture repeats were found in the condor genome. Using condor BAC library and clones, chicken-condor comparative maps were generated. A condor fibroblast cell line transcriptome was characterized using the 454 sequencing technology. Our karyotypic analyses of the sparrow in combination with other studies indicate that the rearrangements in both chromosomes 2 m and 3 a are complex and likely involve multiple inversions, interchromosomal linkage, and pleiotropy. At least a portion of the rearrangement in chromosome 2 m existed in the common ancestor of the four North American species of Zonotrichia , but not in the one South American species, and that the 2 m form, originally thought to be the derived condition, might actually be the ancestral one. Conclusion Mining and characterization of candidate loci in the California condor using molecular genetic and genomic techniques as well as linkage and comparative genomic mapping will eventually enable the identification of carriers of the chondrodystrophy allele, resulting in improved genetic management of this disease. In the white-throated sparrow, genomic studies, combined with ecological data, will help elucidate the basis of genic selection in a natural population. Morphs of the sparrow provide us with a unique opportunity to study intraspecific genomic differences, which have resulted from two separate yet linked evolutionary trajectories. Such results can transform our understanding of evolutionary and conservation biology.

Ursolic acid (UA), a pentacyclic triterpenoid widely found in medicinal herbs and fruits, has been reported to possess a wide range of beneficial properties including anti-hyperglycemia, anti-obesity, and anti-cancer. However, the molecular mechanisms underlying the action of UA remain largely unknown. Here we show that UA inhibits leucine-induced activation of the mechanistic target of rapamycin complex 1 (mTORC1) signaling pathway in C2C12 myotubes. The UA-mediated inhibition of mTORC1 is independent of Akt, tuberous sclerosis complex 1/2 (TSC1/2), and Ras homolog enriched in brain (Rheb), suggesting that UA negatively regulates mTORC1 signaling by targeting at a site downstream of these mTOR regulators. UA treatment had no effect on the interaction between mTOR and its activator Raptor or inhibitor Deptor, but suppressed the binding of RagB to Raptor and inhibited leucine-induced mTOR lysosomal localization. Taken together, our study identifies UA as a direct negative regulator of the mTORC1 signaling pathway and suggests a novel mechanism by which UA exerts its beneficial function.