The sperm storage capacity in hens was correlated with the morphological differences of the oviduct and uterus-vagina junction

The fertilization rate is an important index to evaluate the reproductive capacity of hens, which is mainly affected by semen quality, timing of artificial insemination (AI), and the ability to store sperm. A high sperm storage (SS) capacity can extend the interval, reduce the frequency, and decrease the labor costs of AI. However, relatively few studies have investigated the SS capacity of hens. Therefore, the aims of the present study were to identify factors influencing the SS capacity of Guangxi partridge chickens and to explore the impact of the sperm count in different sections of the oviduct and sperm storage tubules (SSTs), in addition to the number and surface area of SSTs on SS capacity at different time points after AI. We found that SS capacity was positively correlated to the egg production rate (P < 0.01) and body length (P < 0.05). On post-AI days 5, 10, and 15, the sperm count was higher in uterus-vagina junction (UVJ) than the magnum, isthmus, and infundibulum (P < 0.01), but gradually decreased over time. Also, the duration of SS and the sperm count of the UVJ was greater in the high SS group than the low SS group (P < 0.05). Histopathological analysis of the UVJ showed that the number and surface area of the SSTs (P < 0.01), as well as the proportion of SSTs containing sperm, were greater in the high SS group at all time points post AI (P < 0.01), while the proportion of SSTs containing sperm gradually decreased over time. Collectively, these results highlight the potential for selective breeding of SS capacity and show that SS capacity is related to laying performance and body length of Guangxi partridge hens. In addition, SS capacity was positively correlated to the surface area of SSTs and the proportion containing sperm. A greater sperm count stored in the UVJ was correlated to more sperm transported to the infundibulum and subsequent greater SS capacity of hens.

Identification of genes associated with sperm storage capacity in hens at different times after insemination by RNA-seq and Ribo-seq

BACKGROUND

Sperm storage capacity (SSC) determines the duration of fertility in hens and is an important reproduction trait that cannot be ignored in production. Currently, the genetic mechanism of SSC is still unclear in hens. Therefore, to explore the genetic basis of SSC, we analyzed the uterus-vagina junction (UVJ) of hens with different SSC at different times after insemination by RNA-seq and Ribo-seq.

RESULTS

Our results showed that 589, 596, and 527 differentially expressed genes (DEGs), 730, 783, and 324 differentially translated genes (DTGs), and 804, 625, and 467 differential translation efficiency genes (DTEGs) were detected on the 5th, 10th, and 15th days after insemination, respectively. In transcription levels, we found that the differences of SSC at different times after insemination were mainly reflected in the transmission of information between cells, the composition of intercellular adhesion complexes, the regulation of ion channels, the regulation of cellular physiological activities, the composition of cells, and the composition of cell membranes. In translation efficiency (TE) levels, the differences of SSC were mainly related to the physiological and metabolic activities in the cell, the composition of the organelle membrane, the physiological activities of oxidation, cell components, and cell growth processes. According to pathway analysis, SSC was related to neuroactive ligand-receptor interaction, histidine metabolism, and PPAR signaling pathway at the transcriptional level and glutathione metabolism, oxidative phosphorylation, calcium signaling pathway, cell adhesion molecules, galactose metabolism, and Wnt signaling pathway at the TE level. We screened candidate genes affecting SSC at transcriptional levels (COL4A4, MUC6, MCHR2, TACR1, AVPR1A, COL1A1, HK2, RB1, VIPR2, HMGCS2) and TE levels(COL4A4, MUC6, CYCS, NDUFA13, CYTB, RRM2, CAMK4, HRH2, LCT, GCK, GALT). Among them, COL4A4 and MUC6 were the key candidate genes differing in transcription, translation, and translation efficiency.

CONCLUSIONS

Our study used the combined analysis of RNA-seq and Ribo-seq for the first time to investigate the SSC and reveal the physiological processes associated with SSC. The key candidate genes affecting SSC were screened, and the theoretical basis was provided for the analysis of the molecular regulation mechanism of SSC.

Evolutionary diversification of defensins and cathelicidins in birds and primates

Divergent evolution for more than 310 million years has resulted in an avian immune system that is complex and more compact than that of primates, sharing much of its structure and functions. Not surprisingly, well conserved ancient host defense molecules, such as defensins and cathelicidins, have diversified over time. In this review, we describe how evolution influenced the host defense peptides repertoire, its distribution, and the relationship between structure and biological functions. Marked features of primate and avian HDPs are linked to species-specific characteristics, biological requirements, and environmental challenge.

Long-term sperm storage in eusocial Hymenoptera

In internally fertilizing species, sperm transfer is not always immediately followed by egg fertilization, and female sperm storage (FSS) may occur. FSS is a phenomenon in which females store sperm in a specialized organ for periods lasting from a few hours to several years, depending on the species. Eusocial hymenopterans (ants, social bees, and social wasps) hold the record for FSS duration. In these species, mating takes place during a single nuptial flight that occurs early in adult life for both sexes; they never mate again. Males die quickly after copulation but survive posthumously as sperm stored in their mates' spermathecae. Reproductive females, also known as queens, have a much longer life expectancy, up to 20 years in some species. Here, we review what is currently known about the molecular adaptations underlying the remarkable FSS capacities in eusocial hymenopterans. Because sperm quality is crucial to the reproductive success of both sexes, we also discuss the mechanisms involved in sperm storage and preservation in the male seminal vesicles prior to ejaculation. Finally, we propose future research directions that should broaden our understanding of this unique biological phenomenon.

Transcriptome analysis and identification of genes associated with individual fertilization rate differences in hen infundibulum

1. Fertilisation rate is closely related to the reproductive performance and economic status of chicken laying breeders. In this study, two flocks (n = 1,029 in population I and n = 358 in population II) in the later laying period were used for investigating the individual differences among population fertilisation rates (FRs).2. The funnel and distal parts of the infundibulum were collected from nine individuals (five with low FR and four with high FR from population II) and RNA-sequencing (RNA-seq) method was used to investigate the transcriptome differences in fertilisation. Differences in fertilisation regulation were investigated by comparing the different parts (funnel and distal) of the infundibulum between the low FR and high FR groups.3. There were notable individual FR differences in both categories. Some individuals had a relative high FR (≥90%) for a long time (>5 days after AI), contrarily, some individuals lost the ability to fertilise eggs in a very short time.4. Differentially expressed genes (DEGs), such as DUSP7, PPP1R3B, FYB, OVA, OVALX and OVALY may be associated with sperm functional regulation, fertilisation and early-stage fertilised ovum development processes. DEGs such as AVBD1, AVBD2, AVBD6, NFATC2 and BANK1 indicated a severe immune response to sperm survival and fertilisation in the oviduct.5. The results suggested that individual differences should be considered in the breeding and reproduction process. The DEGs identified in this study may promote our understanding of different fertilisation regulation in laying breeders.

Transcriptomic and metabolomic insights into the variety of sperm storage in oviduct of egg layers

In birds, the sperm storage tubules (SST) are dispersed in uterovaginal junction (UVJ) and highly correlated with differential capacity of sperm storage (SS) in and among species with unspecified mechanisms. Here, the SS duration of 252 egg layer breeders was evaluated in 5 rounds with 3 phenotypic traits to screen high- and low-SS individuals, respectively, followed with transcriptome of UVJ tissues and metabolome of serum (high-SS vs. low-SS) to decipher the candidate genes and biochemical markers correlated with differential SS capacity. Histological characterization suggested slightly higher density of SST in UVJ (high-SS vs. low-SS). Transcriptome analyses identified 596 differentially expressed genes (336 upregulated vs. 260 downregulated), which were mainly enriched in gene ontology terms of homeostasis, steroid and lipid metabolism and hormone activity, and 12 significant pathways (P < 0.05) represented by calcium, steroid, and lipid metabolism. Immunohistochemical staining of GNAQ, ST6GAL1, ADFP, and PCNA showed similar distribution in UVJ tissues between 2 groups. Several candidates (HSD11B2, DIO2, AQP3, GNAQ, NANS, ST6GAL1) combined with 4 (11β-prostaglandin F2α, prostaglandin B1, 7α-hydroxytestosterone, and N-acetylneuraminic acid) of 40 differential metabolites enriched in serum metabolome were considered as regulators and biomarkers of SS duration in egg layer breeders. The integrated transcriptome and metabolome analyses of chicken breeder hens will provide novel insights for exploration and improvement of differential SS capacity in birds.

Microbiota, Gut Health and Chicken Productivity: What Is the Connection?

Gut microbiota and its relationship to animal health and productivity in commercial broiler chickens has been difficult to establish due to high variability between flocks, which derives from plenty of environmental, nutritional, and host factors that influence the load of commensal and pathogenic microbes surrounding birds during their growth cycle in the farms. Chicken gut microbiota plays a key role in the maintenance of intestinal health through its ability to modulate host physiological functions required to maintain intestinal homeostasis, mainly through competitive exclusion of detrimental microorganisms and pathogens, preventing colonization and therefore decreasing the expense of energy that birds normally invest in keeping the immune system active against these pathogens. Therefore, a “healthy” intestinal microbiota implies energy saving for the host which translates into an improvement in productive performance of the birds. This review compiles information about the main factors that shape the process of gut microbiota acquisition and maturation, their interactions with chicken immune homeostasis, and the outcome of these interactions on intestinal health and productivity.

Overexpressing ovotransferrin and avian β-defensin-3 improves antimicrobial capacity of chickens and poultry products

Zoonotic and foodborne diseases pose a significant burden, decreasing both human and animal health. Modifying chickens to overexpress antimicrobials has the potential to decrease bacterial growth on poultry products and boost chicken innate immunity. Chickens overexpressing either ovotransferrin or avian β-defensin-3 (AvβD3) were generated using Tol-2 transposons. Transgene expression at the RNA and protein level was seen in egg white, breast muscle, and serum. There were significant differences in the immune cell populations in the blood, bursa, and spleen associated with transgene expression including an increased proportion of CD8+ cells in the blood of ovotransferrin and AvβD3 transgenic birds. Expression of the antimicrobials inhibited the in vitro growth of human and chicken bacterial pathogens and spoilage bacteria. For example, transgene expression significantly reduced growth of aerobic and coliform bacteria in breast muscle and decreased the growth of Salmonella enterica in egg white. Overall these results indicate that overexpression of antimicrobials in the chicken can impact the immune system and increase the antimicrobial capacity of poultry products.

Effect of antibiotic withdrawal in feed on chicken gut microbial dynamics, immunity, growth performance and prevalence of foodborne pathogens

Development of antibiotic resistance in foodborne pathogens, Salmonella spp. and Campylobacter, is a public health concern. Public demand to reduce the use of sub-therapeutic antibiotic growth promoters (AGP) in poultry feeding has resulted in greater adoption of antibiotic-free poultry production systems. There is a need to understand the effects of AGP removal from poultry feed on gut microbiota and its impact on prevalence of foodborne pathogens. The effect of antibiotic withdrawal from poultry feed on gut microbial community, host performance and immunity, and prevalence of Salmonella and Campylobacter was evaluated. Birds were raised on three phase diets (starter [d0-22], grower [d23-35] and finisher [d36-42]) with and without bacitracin dimethyl salicyclate (BMD). At early growth stage, bird performance was improved (P ≤ 0.05) with BMD treatment, whereas performance was better (P ≤ 0.05) in control group (no BMD in the feed) at the time of commercial processing. Acetate and butyrate production was affected (P ≤ 0.05) by age, whereas propionate production was affected (P ≤ 0.05) by both the treatment and age. The bacterial communities in the cecum were more diverse (P ≤ 0.001) and rich compared to the ileal communities, and they shifted in parallel to one another as the chicks matured. Differences in diversity and species richness were not observed (P > 0.05) between the BMD-fed and control groups. Comparing all ages, treatments and diets, the composition of cecal and ileal bacterial communities was different (P ≤ 0.001). Inclusion of BMD in the feed did not affect the bacterial phyla. However, predictable shift in the ileal and cecal bacterial population at lower taxonomic level was observed in control vs BMD-fed group. Cytokines gene expression (IL-10, IL-4, IFN-γ, beta-defensin, and TLR-4) was affected (P≤ 0.05) in the BMD-fed group at early stages of growth. The prevalence of foodborne pathogens, Campylobacter spp. and Salmonella spp. showed higher abundance in the ilea of BMD-fed chicks compared to control group. Overall, this study provided insight of the impact of AGP supplementation in the feed on gut microbial modulations, bird performance, host immunity and pathogen prevalence. This information can assist in designing alternative strategies to replace antibiotics in modern poultry production and for food safety.

Expression profiles of human epididymis epithelial cells reveal the functional diversity of caput, corpus and cauda regions

STUDY HYPOTHESIS

Region-specific transcriptional profiling of tissues and cultured epithelial cells from the human epididymis will predict functional specialization along the duct.

STUDY FINDING

We identified the molecular signature driving functions of the caput, corpus and cauda epithelium, and determined how these differ to establish the regional differentiation of the organ.

WHAT IS KNOWN ALREADY

The epithelium lining the human male genital ducts has a critical role in fertility. In particular, it controls the luminal environment in the epididymis, which is required for normal sperm maturation and reproductive competence. Studies in many animal species have largely informed our understanding of the molecular basis of epididymis function. However, there are substantial differences between species.

STUDY DESIGN, SAMPLES/MATERIALS, METHODS

Using RNA sequencing on biological replicates, we described gene expression profiles for tissue from each region of the epididymis and cultured epithelial cells derived from these regions. Bioinformatic tools were then utilized to identify differentially expressed genes (DEGs) between tissues and cells from the caput, corpus and cauda.

MAIN RESULTS AND THE ROLE OF CHANCE

The data showed that the caput is functionally divergent from the corpus and cauda, which have very similar transcriptomes. Interrogation of DEGs using gene ontology process enrichment analyses showed that processes of ion transport, response to hormone stimulus and urogenital tract development are more evident in the caput, while defense response processes are more important in the corpus/cauda. Consistent with these regional differences in epididymis function, we observed differential expression of transcription factors in the caput and corpus/cauda.

LIMITATIONS, REASONS FOR CAUTION

Cultured caput, corpus and cauda cells may not faithfully represent the same cells in the intact organ, due to loss of hormonal signals from the testis and communication from other cell types.

WIDER IMPLICATIONS OF THE FINDINGS

Our data provide a molecular characterization that will facilitate advances in understanding human epididymis epithelium biology in health and disease. They may also reveal the mechanisms coordinating epididymis luminal environment and sperm maturation.

LARGE SCALE DATA

Data deposited at http://www.ncbi.nlm.nih.gov/geo/GSE72986.

STUDY FUNDING AND COMPETING INTERESTS

This work was supported by the National Institutes of Health: R01HD068901 (PI: A.H.). The authors declare no conflict of interest.

Activation of innate immune system in response to lipopolysaccharide in chicken Sertoli cells

Sertoli cells (SCs) play an important physiological role in the testis, as they support, nourish, and protect the germ cells. As protection of the developing spermatozoa is an emerging aspect of reproductive physiology, this study examined the expression pattern of innate immune-related genes, including avian β-defensins (AvBDs), Toll-like receptors (TLRs), and cytokines, and investigated the time course of an inflammatory response in rooster SCs triggered by exposure to the bacterial endotoxin lipopolysaccharide (LPS). SCs were isolated from 6-week-old chicken, culturedin vitro, and stimulated with 1 μg/ml LPS at different time courses (0, 6, 12, 24, and 48 h). Data on expression analysis revealed that all ten members of the chickenTLRfamily, nine members of theAvBDfamily, as well as eight cytokine genes were expressed in SCs. Quantitative real-time PCR analysis revealed that LPS treatment resulted in significant induction of the expression levels of sixTLRs, sixAvBDs, and four cytokine genes, while two cytokine genes were downregulated and two other genes were unchanged. The increasing interleukin 1β (IL1β) production was confirmed in the conditioned medium. Furthermore, the phagocytosis of SCs was increased after LPS treatment. In conclusion, these findings provide evidence that SCs express innate immune-related genes and respond directly to bacterial ligands. These genes represent an important component of the immune system, which could be integrated into semen, and present a distinctive constituent of the protective repertoire of the testis against ascending infections.

Effects of sexual maturation and Salmonella infection on the expression of avian β-defensin genes in the chicken testis

Rooster infertility is a major concern in the poultry industry and protection of the male reproductive organs from pathogens is an essential aspect of reproductive physiology. During the last years, research on antimicrobial protection has elucidated the critical role of the antimicrobial peptides avian β-defensins (AvBDs) in the innate immunity in chickens. AvBDs have been reported to be expressed in the hen reproductive organs, providing protection against microbial pathogens including Salmonella Enteritidis (SE). However, mechanisms of antimicrobial protection of rooster reproductive organs and especially the testis, mediated by AvBDs are poorly understood. The aim of this study was to investigate the expression of the complete family of the 14 AvBD genes, in the rooster testis in vivo, to determine whether sexual maturation affects their testicular mRNA abundance and to investigate whether SE infection alters their expression. Expression analysis revealed that 9 members of the AvBD family, namely AvBD1, 2, 4, 5, 6, 9, 10, 12 and 14 were expressed in the testis. Quantitative real-time PCR analysis revealed that the mRNA abundance of three AvBDs was up regulated and of three AvBDs was down regulated with respect to sexual maturation. In addition, SE infection resulted in a significant induction of AvBD4, 10, 12 and 14 in the testis of sexually mature roosters. These findings provide strong evidence to suggest that an AvBD-mediated immune response mechanism exists in the rooster testis providing protection against bacterial pathogens including Salmonella species.

A novel subclass of bovine β-defensins links reproduction and immunology

β-defensins are effector molecules of the innate immune system, found in many diverse species. Their presence in invertebrates as well as vertebrates suggests highly conserved functional roles. Most β-defensins are believed to act as antimicrobial agents at epithelial surfaces, although additional functions have also been described, including immune regulatory activity, wound repair and a role in coat-colour determination. High expression of β-defensins have been found in testis and epididymidal epithelium as well as in the seminal fluid of humans, macaque, rat, mouse and cow. Human and macaque β-defensins have recently been shown to affect sperm motility while a mutation in β-defensin 126 is associated with reduced fertility in men. Genetic variation in bovine defensin genes may explain the increased incidence of low fertility in cattle. Here, we present a summary of the known functions of β-defensins as well as their emerging role in reproduction and their potential to improve fertility in cattle.

Avian host defense peptides

Host defense peptides (HDPs) are important effector molecules of the innate immune system of vertebrates. These antimicrobial peptides are also present in invertebrates, plants and fungi. HDPs display broad-spectrum antimicrobial activities and fulfill an important role in the first line of defense of many organisms. It is becoming increasingly clear that in the animal kingdom the functions of HDPs are not confined to direct antimicrobial actions. Research in mammals has indicated that HDPs have many immunomodulatory functions and are also involved in other physiological processes ranging from development to wound healing. During the past five years our knowledge about avian HDPs has increased considerably. This review addresses our current knowledge on the evolution, regulation and biological functions of HDPs of birds.

Expression of avian β-defensins and Toll-like receptor genes in the rooster epididymis during growth and Salmonella infection

The epididymis is an organ involved in the maturation, transport, and storage of sperm prior to ejaculation. As epididymis is exposed to a constant risk of inflammatory conditions that may lead to transient or permanent sterility, protection of this organ from pathogens is an essential aspect of reproductive physiology. The families of antimicrobial peptides β-defensins and the pattern-recognition receptors Toll-like (TLR) mediate innate immunity in various vertebrates including avian species. As rooster infertility is a major concern in the poultry industry, the objectives of this study were to determine the expression profile of the entire family of the avian β-defensins (AvBD) and TLR genes in the rooster epididymis, to investigate whether sexual maturation affects their epididymidal mRNA abundance and to determine the changes in their expression levels in response to Salmonella enteritidis (SE) infection in the epididymis of sexually mature roosters. RNA was extracted from the epididymis of healthy pubertal, sexually mature and aged birds, and from sexually mature SE infected birds. RT-PCR analysis revealed that 10 members of the AvBD and nine members of the TLR gene families were expressed in the epididymis. Quantitative real-time PCR analysis revealed that the epididymidal mRNA abundance of certain AvBD and TLR genes was developmentally regulated with respect to sexual maturation. SE infection resulted in a significant induction of AvBD 1, 9, 10, 12 and 14, as well as TLR 1-2, 2-1, 2-2, 4, 5 and 7 genes, in the epididymis of sexually mature roosters, compared to healthy birds of the same age. These findings provide strong evidence to suggest that the rooster epididymis is capable of initiating an inflammatory response to Salmonella, through activation of certain members of the AvBD and TLR gene families.

A novel beta-defensin antimicrobial peptide in Atlantic cod with stimulatory effect on phagocytic activity

A novel defensin antimicrobial peptide gene was identified in Atlantic cod, Gadus morhua. This three exon/two intron defensin gene codes for a peptide precursor consisting of two domains: a signal peptide of 26 amino acids and a mature peptide of 40 residues. The mature cod defensin has six conserved cysteine residues that form 1–5, 2–4 and 3–6 disulphide bridges. This pattern is typical of beta-defensins and this gene was therefore named cod beta-defensin (defb). The tertiary structure of Defb exhibits an α/β fold with one α helix and β₁β₂β₃ sheets_. RT-PCR analysis indicated that defb transcripts were present mainly in the swim bladder and peritoneum wall but could also be detected at moderate to low levels in skin, head- and excretory kidneys. In situ hybridisation revealed that defb was specifically expressed by cells located in the swim bladder submucosa and the oocytes. During embryonic development, defb gene transcripts were detectable from the golden eye stage onwards and their expression was restricted to the swim bladder and retina. Defb was differentially expressed in several tissues following antigenic challenge with Vibrio anguillarum, being up-regulated up to 25-fold in head kidney. Recombinant Defb displayed antibacterial activity, with a minimal inhibitory concentration of 0.4–0.8 µM and 25–50 µM against the Gram-(+) bacteria Planococcus citreus and Micrococcus luteus, respectively. In addition, Defb stimulated phagocytic activity of cod head kidney leucocytes invitro. These findings imply that beta-defensins may play an important role in the innate immune response of Atlantic cod.

Multifunctional glycoprotein DEFB126--a curious story of defensin-clad spermatozoa

During maturation, the surface of mammalian spermatozoa undergoes dramatic changes leading to the acquisition of properties vital for survival and performance in the female reproductive tract. A prominent change is the addition to the sperm surface of an atypical β-defensin polypeptide. In primates, the β-defensin DEFB126 becomes adsorbed to the entire sperm surface as spermatozoa move through the epididymal duct. DEFB126 has a conserved β-defensin core and a unique long glycosylated peptide tail. The carbohydrates of this domain contribute substantially to the sperm glycocalyx. DEFB126 is critical for efficient transport of sperm in the female reproductive tract, preventing their recognition by the female immune system, and might facilitate the delivery of capacitated sperm to the site of fertilization. A newly discovered dinucleotide deletion in the human DEFB126 gene is unusually common in diverse populations and results in a null allele. Predictably, men who are homozygous for the deletion produce sperm with an altered glycocalyx and impaired function, and have reduced fertility. Insights into the biology of DEFB126 are contributing to a better understanding of reproductive fitness in humans, as well as the development of diagnostics and therapeutics for male infertility.

Maturational changes in the survivability and fertility of fowl sperm during their passage through the male reproductive tract

The objective of this study was to examine whether domestic fowl (Gallus domesticus) sperm undergo maturation in their capacity for survival and fertilization in the male reproductive tract. Sperm collected from the testis, epididymis and the proximal, middle and distal vas deferens were simultaneously stored in vitro in minimum essential medium (MEM) at 39°C for 0, 3 and 6h, and at 4°C for 24 and 48h. Sperm membrane integrity was measured using the dual fluorescent stain SYBR-14/propidium iodide (PI). Aliquots of sperm from the various sites were subjected to artificial insemination (AI) into the uteri of hens to assess the duration of sperm survival in the oviduct and to determine the fertility status of the sperm. Testicular sperm exhibited a very low capacity to survive under in vitro liquid storage conditions, irrespective of the storage temperature used, and in the oviduct, and they had a low ability to fertilize the ovum. On the contrary, sperm from the distal vas deferens had a higher survival rate during in vitro storage periods, a longer life span in the oviduct, and high fertility. Survival and fertilizing capacity of the sperm recovered from the testes increased gradually (P<0.05) from the testes to the distal vas deferens. In conclusion, we suggest that fowl sperm may undergo functional maturation through a process of gradual changes in their survival and fertilization capacities during their passage through the successive parts of the male reproductive tract.

Changes in the expression of Toll-like receptors in the chicken testis during sexual maturation and Salmonella infection

Rooster infertility is a major concern in the poultry industry and chicken male reproductive organs are the infectious tissues of various pathogenic microorganisms. Protection of the chicken male reproductive organs from pathogens is therefore an essential aspect of reproductive physiology. Recently Toll-like receptors (TLRs) have been identified as one of the key components of innate immunity in vertebrate species and have been reported to be expressed in the reproductive organs in various female species, including the chicken. However, mechanisms of antimicrobial protection of male reproductive organs mediated by TLRs are poorly understood. The objectives of this study were to determine the expression profile of the entire family of the ten chicken TLR genes in the chicken testis, to investigate whether sexual maturation affects their testicular mRNA abundance and to determine the changes in their expression levels in response to Salmonella enteritidis (SE) infection. RNA was extracted from the testis of healthy pre-pubertal, sexually mature and aged birds, and from sexually mature SE infected birds. RT-PCR analysis revealed that all TLRs, apart from TLR1-1 (TLR6), were expressed in the chicken testis. Quantitative real-time PCR analysis revealed that the testicular mRNA abundance of certain TLRs was developmentally regulated with respect to sexual maturation, while SE infection resulted in a significant induction of TLR2-1, 4, 5, 15 and 21 in the testis of sexually mature birds compared, to healthy birds of the same age. These findings provide strong evidence to suggest a key role of TLRs in the innate immune responses of chicken testis against Salmonella colonization.

Expression of Toll-like receptors and avian β-defensins and their changes in response to bacterial components in chicken sperm

The aim of the present study was to examine whether chicken sperm express mRNA of Toll-like receptors (TLR) and avian β-defensins (avBD), and whether the expression of avBD in the sperm are regulated by the interaction of TLR-2 and TLR-4 with their corresponding ligands. Total RNA was extracted from fresh sperm and mRNA expression for TLR and avBD were examined by reverse-transcription PCR. Changes in the expression of avBD-5, avBD-9, avBD-10, and avBD-12 in the sperm after incubation with lipopolysaccharide (LPS; TLR-4 ligand) or lipopeptide (Pam3CSK4; TLR-2 ligand) were examined by real-time PCR. Among 8 types of TLR, PCR products of 7 types, namely, TLR-2 to TLR-5, TLR-7, TLR-15, and TLR-21, were identified in the sperm. The sperm also expressed cluster of differentiation 14 (CD14), which is required for the binding of LPS to TLR-4. Out of 14 avBD types reported in the chicken, a total of 9 types, namely, avBD-1, avBD-3, avBD-5, and avBD-7 to avBD-12 were expressed by the sperm, whereas avBD-5, avBD-9, avBD-10, and avBD-12 showed dense signals on the gel. Expression levels of avBD-5, avBD-9, avBD-10, and avBD-12 were significantly increased in the sperm stimulated with LPS, and that of avBD-5 was also enhanced by Pam3CSK4. These results suggest that avian sperm have the ability of the innate host defense to protect themselves from infection in the male and female genital tracts.

Expression of chicken LEAP-2 in the reproductive organs and embryos and in response to Salmonella enterica infection

In recent years host antimicrobial peptides and proteins have been recognised as key mediators of the innate immune response in many vertebrate species, providing the first line of defense against potential pathogens. In chickens a number of cationic antimicrobial peptides have been recently identified. However, although these peptides have been studied extensively in the avian gastrointestinal tract, little is known about their function in the chicken reproductive organs and embryos. Chicken Liver Expressed Antimicrobial Peptide-2 (cLEAP-2) has been previously reported to function in protecting birds against microbial attack. The aim of this study was to investigate the expression of cLEAP-2 gene in the chicken reproductive organs, as well as in chicken embryos during embryonic development, and to determine whether cLEAP-2 expression in the chicken reproductive organs was constitutive or induced as a response to Salmonella enteritidis infection. RNA was extracted from ovary, oviduct, testis and epididymis of sexually mature healthy and Salmonella infected birds, as well as from chicken embryos until day ten of embryonic development. Expression analysis data revealed that cLEAP-2 was expressed in the chicken ovary, testis and epididymis as well as in embryos during early embryonic development. Quantitative real-time PCR analysis revealed that cLEAP-2 expression was constitutive in the chicken epididymis, but was significantly up regulated in the chicken gonads, following Salmonella infection. In addition, expression of cLEAP-2 during chicken embryogenesis appeared to be developmentally regulated. These data provide evidence to suggest a key role of cLEAP-2 in the protection of the chicken reproductive organs and the developing embryos from Salmonella colonization.