Response of restraint stress-selected lines of Japanese quail to heat stress and Escherichia coli challenge

Identification of SNPs Associated with Stress Response Traits within High Stress and Low Stress Lines of Japanese Quail

Mitigation of stress is of great importance in poultry production, as chronic stress can affect the efficiency of production traits. Selective breeding with a focus on stress responses can be used to combat the effects of stress. To better understand the genetic mechanisms driving differences in stress responses of a selectively bred population of Japanese quail, we performed genomic resequencing on 24 birds from High Stress (HS) and Low Stress (LS) lines of Japanese quail using Illumina HiSeq 2 × 150 bp paired end read technology in order to analyze Single Nucleotide Polymorphisms (SNPs) within the genome of each line. SNPs are common mutations that can lead to genotypic and phenotypic variations in animals. Following alignment of the sequencing data to the quail genome, 6,364,907 SNPs were found across both lines of quail. 10,364 of these SNPs occurred in coding regions, from which 2886 unique, non-synonymous SNPs with a SNP% ≥ 0.90 and a read depth ≥ 10 were identified. Using Ingenuity Pathway Analysis, we identified genes affected by SNPs in pathways tied to immune responses, DNA repair, and neurological signaling. Our findings support the idea that the SNPs found within HS and LS lines of quail could direct the observed changes in phenotype.

Japanese quail (Coturnix japonica) as a novel model to study the relationship between the avian microbiome and microbial endocrinology-based host-microbe interactions

BACKGROUND

Microbial endocrinology, which is the study of neuroendocrine-based interkingdom signaling, provides a causal mechanistic framework for understanding the bi-directional crosstalk between the host and microbiome, especially as regards the effect of stress on health and disease. The importance of the cecal microbiome in avian health is well-recognized, yet little is understood regarding the mechanisms underpinning the avian host-microbiome relationship. Neuroendocrine plasticity of avian tissues that are focal points of host-microbiome interaction, such as the gut and lung, has likewise received limited attention. Avian in vivo models that enable the study of the neuroendocrine dynamic between host and microbiome are needed. As such, we utilized Japanese quail (Coturnix japonica) that diverge in corticosterone response to stress to examine the relationship between stress-related neurochemical concentrations at sites of host-microbe interaction, such as the gut, and the cecal microbiome.

RESULTS

Our results demonstrate that birds which contrast in corticosterone response to stress show profound separation in cecal microbial community structure as well as exhibit differences in tissue neurochemical concentrations and structural morphologies of the gut. Changes in neurochemicals known to be affected by the microbiome were also identified in tissues outside of the gut, suggesting a potential relationship in birds between the cecal microbiome and overall avian physiology.

CONCLUSIONS

The present study provides the first evidence that the structure of the avian cecal microbial community is shaped by selection pressure on the bird for neuroendocrine response to stress. Identification of unique region-dependent neurochemical changes in the intestinal tract following stress highlights environmental stressors as potential drivers of microbial endocrinology-based mechanisms of avian host-microbiome dialogue. Together, these results demonstrate that tissue neurochemical concentrations in the avian gut may be related to the cecal microbiome and reveal the Japanese quail as a novel avian model in which to further examine the mechanisms underpinning these relationships. Video abstract.

75-kDa glucose-regulated protein (GRP75) is a novel molecular signature for heat stress response in avian species

Glucose-regulated protein 75 (GRP75) was first characterized in mammals as a heat shock protein-70 (HSP70) family stress chaperone based on its sequence homology. Extensive studies in mammals showed that GRP75 is induced by various stressors such as glucose deprivation, oxidative stress, and hypoxia, although it remained unresponsive to the heat shock. Such investigations are scarce in avian (nonmammalian) species. We here identified chicken GRP75 by using immunoprecipitation assay integrated with LC-MS/MS, and found that its amino acid sequence is conserved with high homology (52.5%) to the HSP70 family. Bioinformatics and 3D-structure prediction indicate that, like most HSPs, chicken GRP75 has two principal domains (the NH2-terminal ATPase and COOH-terminal region). Immunofluorescence staining shows that GRP75 is localized predominantly in the avian myoblast and hepatocyte mitochondria. Heat stress exposure upregulates GRP75 expression in a species-, genotype-, and tissue-specific manner. Overexpression of GRP75 reduces avian cell viability, and blockade of GRP75 by its small molecular inhibitor MKT-077 rescues avian cell viability during heat stress. Taken together, this is the first evidence showing that chicken GRP75, unlike its mammalian ortholog, is responsive to heat shock and plays a key role in cell survival/death pathways. Since modern avian species have high metabolic rates and are sensitive to high environmental temperature, GRP75 could open new vistas in mechanistic understanding of heat stress responses and thermotolerance in avian species.

Research Note: Role of the hippocampus in spatial memory in Japanese quail

The Japanese quail is a powerful model to characterize behavioral, physiological, and neurobiological processes in Galliformes. Behavioral tests have already been adapted for quail to assess memory systems, but despite the pivotal role of the hippocampus in this cognitive process, its involvement in spatial memory has not been demonstrated in this species. In this study, lesions were created in the hippocampus of Japanese quail, and both lesioned and control quail were tested for spatial and cue-based learning performances. These hippocampal lesions specifically impacted spatial learning performance, but spared learning performance when birds could solve the task using their cue-based memory. These findings, thus, highlight that the hippocampus plays a crucial role and is essential for spatial declarative memory. Future studies could aim to elucidate the cellular or molecular mechanisms involved in this form of memory.

Copy number variation study in Japanese quail associated with stress related traits using whole genome re-sequencing data

Copy number variation (CNV) is a major driving factor for genetic variation and phenotypic diversity in animals. To detect CNVs and understand genetic components underlying stress related traits, we performed whole genome re-sequencing of pooled DNA samples of 20 birds each from High Stress (HS) and Low Stress (LS) Japanese quail lines using Illumina HiSeq 2×150 bp paired end method. Sequencing data were aligned to the quail genome and CNVnator was used to detect CNVs in the aligned data sets. The depth of coverage for the data reached to 41.4x and 42.6x for HS and LS birds, respectively. We identified 262 and 168 CNV regions affecting 1.6 and 1.9% of the reference genome that completely overlapped 454 and 493 unique genes in HS and LS birds, respectively. Ingenuity pathway analysis showed that the CNV genes were significantly enriched to phospholipase C signaling, neuregulin signaling, reelin signaling in neurons, endocrine and nervous development, humoral immune response, and carbohydrate and amino acid metabolisms in HS birds, whereas CNV genes in LS birds were enriched in cell-mediated immune response, and protein and lipid metabolisms. These findings suggest CNV genes identified in HS and LS birds could be candidate markers responsible for stress responses in birds.

Behavioral phenotype relates to physiological differences in immunological and stress responsiveness in reactive and proactive birds

It has now been demonstrated in many species that individuals display substantial variation in coping styles, generally separating into two major behavioral phenotypes that appear to be linked to the degree of physiological stress responsiveness. Laying hens are perfect examples of these dichotomous phenotypes; white laying hens are reactive, flighty, and exhibit large hormonal and behavioral responses to both acute and chronic stress, while brown laying hens are proactive, exploratory, and exhibit low hormonal and behavioral responses to stress. Given the linkages between stress physiology and many other body systems, we hypothesized that behavioral phenotype would correspond to additional physiological responses beyond the stress response, in this case, immunological responses. Because corticosterone is widely known to be immunosuppressive, we predicted that the reactive white hens would show more dampened immune responses than the proactive brown hens due to their exposure to higher levels of corticosterone throughout life. To assess immune function in white and brown hens, we compared febrile responses, corticosterone elevations, feed consumption, and egg production that occurred in response an injection of lipopolysaccharide (LPS) or saline, inflammatory responses to phytohemagglutinin (PHA) injection in the toe web, innate phagocytic activity in whole blood, and antibody responses to an injection of Sheep Red Blood Cells (SRBCs). Contrary to our predictions, white hens had significantly greater swelling of the toe web in response to PHA and showed a greater inhibition of feeding and reproductive output in response to LPS. These results indicated that reactive individuals are more reactive in both stress and immunological responsiveness.

Tissue distribution, gender- and genotype-dependent expression of autophagy-related genes in avian species

As a result of the genetic selection of broiler (meat-type breeders) chickens for enhanced growth rate and lower feed conversion ratio, it has become necessary to restrict feed intake. When broilers are fed ad libitum, they would become obese and suffer from several health-related problems. A vital adaptation to starvation is autophagy, a self-eating mechanism for recycling cellular constituents. The autophagy pathway has witnessed dramatic growth in the last few years and extensively studied in yeast and mammals however, there is a paucity of information in avian (non-mammalian) species. Here we characterized several genes involved in autophagosome initiation and elongation in Red Jungle fowl (Gallus gallus) and Japanese quail (coturnix coturnix Japonica). Both complexes are ubiquitously expressed in chicken and quail tissues (liver, leg and breast muscle, brain, gizzard, intestine, heart, lung, kidney, adipose tissue, ovary and testis). Alignment analysis showed high similarity (50.7 to 91.5%) between chicken autophagy-related genes and their mammalian orthologs. Phylogenetic analysis demonstrated that the evolutionary relationship between autophagy genes is consistent with the consensus view of vertebrate evolution. Interestingly, the expression of autophagy-related genes is tissue- and gender- dependent. Furthermore, using two experimental male quail lines divergently selected over 40 generations for low (resistant, R) or high (sensitive, S) stress response, we found that the expression of most studied genes are higher in R compared to S line. Together our results indicate that the autophagy pathway is a key molecular signature exhibited gender specific differences and likely plays an important role in response to stress in avian species.