Proteomic analysis of egg white proteins during the early phase of embryonic development

Integrated OMICs approach reveals energy metabolism pathway is vital for Salmonella Pullorum survival within the egg white

Eggs, an important part of a healthy daily diet, can protect chicken embryo development due to the shell barrier and various antibacterial components within the egg white. Our previous study demonstrated that Salmonella Pullorum, highly adapted to chickens, can survive in the egg white and, therefore, be passed to newly hatched chicks. However, the survival strategy of Salmonella Pullorum in antibacterial conditions remains unknown. The overall transcripts in the egg white showed a large-scale shift compared to LB broth. The expression of common response genes and pathways, such as those involved in iron uptake, biotin biosynthesis, and virulence, was significantly changed, consistent with the other transovarial transmission serovar Enteritidis. Notably, membrane stress response, amino acid metabolism, and carbohydrate metabolism were specifically affected. Additional upregulated functionally relevant genes (JI728_13095, JI728_13100, JI728_17960, JI728_10085, JI728_15605, and nhaA) as mutants confirmed the susceptible phenotype. Furthermore, fim deletion resulted in an increased survival capacity in the egg white, consistent with the downregulated expression. The second-round RNA-Seq analysis of the Δfim mutant in the egg white revealed significantly upregulated genes compared with the wild type in the egg white responsible for energy metabolism located on the hyc and hyp operons regulated by FhlA, indicating the Δfim mutant cannot receive enough oxygen and switched to fermentative growth due to its inability to attach to the albumen surface. Together, this study provides a first estimate of the global transcriptional response of Salmonella Pullorum under antibacterial egg white and highlights the new potential role of fim deletion in optimizing energy metabolism pathways that may assist vertical transmission.

IMPORTANCE

Pullorum disease, causing serious embryo death and chick mortality, results in substantial economic losses worldwide due to transovarial transmission. Egg-borne outbreaks are frequently reported in many countries. The present study has filled the knowledge gap regarding how the specific chicken-adapted pathogen Salmonella Pullorum behaves within the challenging environment of egg white. The deletion of the fim fimbrial system can increase survival in the albumen, possibly by reprogramming metabolism-related gene products, which reveals a new adaptive strategy of pathogens. Moreover, the comparison, including previous research on Salmonella Enteritidis, capable of vertical transmission, aims to provide diversified data sets in the field and further help to implement reasonable and effective measures to improve both food safety and animal health.

Proteomic Analysis of Egg Yolk Proteins During Embryonic Development in Wanxi White Goose

To investigate the alterations of yolk protein during embryonic development in Wanxi white goose, the egg yolk protein composition at days 0, 4, 7, 14, 18, and 25 of incubation (D0, D4, D7, D14, D18, and D25) was analyzed by two-dimensional gel electrophoresis combined with mass spectrometry. A total of 65 spots representing 11 proteins with significant abundance changes were detected. Apolipoprotein B-100, vitellogenin-1, vitellogenin-2-like, riboflavin-binding protein, and serotransferrin mainly participated in nutrient (lipid, riboflavin, and iron ion) transport, and vitellogenin-2-like showed a lower abundance after D14. Ovomucoid-like were involved in endopeptidase inhibitory activity and immunoglobulin binding and exhibited a higher expression after D18, suggesting a potential role in promoting the absorption of immunoglobulin and providing passive immune protection for goose embryos after D18. Furthermore, myosin-9 and actin (ACTB) were involved in the tight junction pathway, potentially contributing to barrier integrity. Serum albumin mainly participated in cytolysis and toxic substance binding. Therefore, the high expression of serum albumin, myosin-9, and ACTB throughout the incubation might protect the developing embryo. Apolipoprotein B-100, vitellogenin-1, vitellogenin-2-like, riboflavin-binding protein, and serotransferrin might play a crucial role in providing nutrition for embryonic development, and VTG-2-like was preferentially degraded/absorbed.

Pheasant hatchability and physicochemical features of egg and extra-embryonic structures depending on eggshell color

The study aimed to analyze the biological value of eggs and extra-embryonic structures affecting pheasant hatchability depending on the eggshell's color. Eggs (1,415) from 62-wk-old pheasants were used. The quality of fresh blue (BL), brown (BR), and green (G) eggs were analyzed. Incubation lasted for 25 d. Thick albumen (d 0, 1, 7, 14), amniotic fluid (d 14, 18), and the yolk (d 0-14) were collected. The pH, viscosity, lysozyme activity, crude protein (CP) content in albumen and amnion, pH, vitelline membrane strength, and fatty acids (FA) content in the yolk were performed. The lowest hatchability was in the BL group, and the highest was in the G group. BL group showed lower eggshell thickness and strength and higher egg weight. In thick albumen and amniotic fluid, the pH decreased with the incubation. In the yolk, there was an increasing trend (P = 0.015), with a decrease on d 18 (P < 0.001). The vitelline membrane strength decreased after 1 d of incubation, excluding BR eggs (P < 0.001). Thick albumen viscosity was higher on d 14 in the G group than in other dates and groups, the lowest in amniotic fluid, and slightly higher in BL and BR eggs. On d 18, amniotic fluid viscosity increased (P < 0.001). The lowest viscosity was indicated in BL eggs (P < 0.001). The lysozyme activity in thick albumen on d 14 was the highest (uniquely in BR and G groups), and the lowest values were found in amniotic fluid on d 14; after four d, the activity increased (P < 0.001). The CP content was higher in the BL group on d 14. In amnion, on d 14, the CP content was the lowest (<1%) and increased on d 18 (P < 0.001). There was a higher FA content (especially UFA) in the G group and a decrease in FA content after d 14 (P < 0.001). It was found that eggs with green eggshells have the highest biological value, and blue eggs are the least useful for incubation.

Fertility detection of unincubated chicken eggs by hyperspectral transmission imaging in the Vis-SWNIR region

Detection of infertile eggs prior to incubation can lead to an increase in the hatchability rate and prevent the wastage of billions of non-fertile eggs ended up by failed incubation. In this study, the feasibility of a line-scan hyperspectral imaging system in the visible and short-wavelength near-infrared region was assessed for early detection of non-fertile eggs on day 0 before incubation. A total of 227 white-shell eggs including 131 fertile and 96 infertile eggs were collected from a flock with similar conditions in terms of hen age, feeding, and management. Hyperspectral images of eggs were captured on day 0 before incubation in a transmittance mode of illumination and then the eggs were incubated in a commercial incubator. The edge detection method was used to segment the egg, including both the white and yolk, from the background, and the image spectral information was extracted from the egg region. After applying various pretreatment methods, different classifiers including soft independent modeling of class analogy (SIMCA), linear discriminant analysis (LDA), quadratic discriminant analysis (QDA), and artificial neural networks (ANN) classifiers were utilized to extract the predictive models. Following the acceptable results of SIMCA analysis accomplished by 1st derivative pretreatment (accuracy of 86.67%), the discrimination power plot was used to select the most informative wavebands. The results showed that by using fewer variables in effective wavebands better performance (precision and accuracy of 92.59% and 93.33%, respectively) could be obtained in comparison with the ANN classifier based on the whole spectral data (precision and accuracy of 89.29% and 91.11%, respectively). This study revealed the potential application of hyperspectral transmittance imaging in the Vis-SWNIR region to discern the fertile and infertile eggs before starting the incubation process.

Changes in physicochemical parameters of duck eggs and extra-embryonic structures during incubation

Duckling embryogenesis should be deepened due to the hatching technology and its modification possibilities. Many changes occur in incubated eggs, which expose the embryo to hazards. The study aimed to analyse the physicochemical properties of eggshell, yolk, thick albumen (TA), and amniotic fluid (AF) of incubated hatching eggs from 52-week-old Cherry Valley ducks. The morphological features of 18 fresh eggs were analysed. Over 28 days, a total of 800 eggs underwent incubation. Eggshell surface temperature and egg weight loss were measured on days 1, 4, 7, 10, 14, 18, 21, and 25. Eggshell, TA, AF, and yolk were collected from eggs at incubation days 1-21 (every week). TA was collected on days 0, 1, and 7, while AF on days 7, 14, and 21. The analysis covered a range of physicochemical parameters. Eggshell thickness decreased with incubation, reaching its lowest point posthatch (P < 0.001). The highest pH for TA was recorded on day 1, while the lowest was on day 7 when comparing days 0, 1, and 7 (P < 0.001). TA pH was consistently higher than in AF (P < 0.001). However, the pH of TA was the highest on day 1 and the lowest on day 7 (P < 0.001). Yolk pH increased from days 1 to 21 (P < 0.001). There was also a noticeable in egg weight loss (0.34% daily) (P < 0.001). Vitelline membrane strength decreased from day 0 to day 1 (P < 0.001). Lysozyme activity in thick albumen on day 7 was higher than on days 0 and 1 (P < 0.001). Lysozyme activity in AF was higher on day 21 than days 7 and 14 (P < 0.001). TA viscosity was highest on day 0 and lowest on day 1, compared to other days (P < 0.001). AF viscosity and CP content exhibited an increase on day 21 as compared to days 7 and 14 (P < 0.001). The CP content in TA was notably higher on day 7 than on days 0 and 1 (P < 0.001). Polyunsaturated fatty acids declined, while monounsaturated and transfatty acids increased (P < 0.001). Viscosity and lysozyme activity increased on day 7 in TA and day 21 in AF. TA and the amniotic cavity appeared to facilitate the transfer of substances, particularly CP. Viscosity could be an indicator for optimising incubation conditions, as incorrect changes can affect embryo mortality. The results showed the different utilisation of nutrients, such as fatty acids. It could support research on the in-ovo administration of various substances.

Glycoblotting enables seamless and straightforward workflow for MALDI-TOF/MS-based sulphoglycomics of N- and O-glycans

Sulfated N- and O-glycans exist in trace levels which are challenging to detect, especially when abundant neutral and sialylated glycans are present. Current matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS)-based sulfoglycomics approaches effectively utilize permethylation to discriminate sulfated glycans from sialyl-glycans. And a charge-based separation to isolate the sulfated glycans from the rest of the permethylated neutral and sialyl-glycans. However, these approaches suffer from concomitant sample losses during cleanup steps. Herein, we describe Glycoblotting as a straightforward complementary method with seamless glycan purification, enrichment, methylation, and labeling on a single platform to address sulfated glycan enrichment, sialic acid methylation, and sample loss. Glycoblottings' on-bead chemoselective ligation of reducing sugars with hydrazide showed excellent recovery of sulfated glycans, allowing the detection of more sulfated glycan species. On-bead methyl esterification of sialic acid using 3-methyl-1-p-tolyltriazene (MTT) effectively discriminates sulfated glycans from sialyl-glycans. Furthermore, we have shown that using MTT as a methylating agent allowed us to simultaneously detect and differentiate sulfate from phosphate groups in isobaric N-glycan species. We believe that Glycoblotting will contribute significantly to the MALDI-TOF MS-based Sulphoglycomics workflow.

The biological value of hatching eggs of broiler chicken in the early-mid incubation period based on physicochemical and morphological features

The study aimed to assess various quality characteristics (physical, morphologic, mechanical) of hatching eggs during the early-mid incubation period. Hatching eggs (1,200) were bought from a broiler Ross 308 breeder flock. Before incubation, 20 eggs were analyzed for dimensions and morphologic composition. Eggs (1,176) were incubated for 21 d. Hatchability was analyzed. On d 1, 2, 4, 6, 8, 10, and 12, eggs were collected (n = 20). The eggshell surface temperature and water loss were measured. The eggshell strength and thickness and the vitelline membrane strength were analyzed. The pH of thick albumen, amniotic fluid, and yolk were determined. The viscosity and lysozyme activity were studied for the thick albumen and amniotic fluid. Water loss was proportional and significantly different between incubation days. The yolk vitelline membrane strength highly depended on incubation days, decreasing steadily within the first 2 d (R² = 0.9643). The albumen pH decreased from d 4 till d 12 of incubation, whereas the yolk pH first increased from d 0 to d 2 before a decline on d 4. Albumen viscosity was highest on d 6. There was a strong dependence of viscosity decrease with increasing shear rate (R² = 0.7976). On the first day of incubation, the highest lysozyme hydrolytic activity was demonstrated (33,790 U/mL) compared to the activity from the amniotic fluid (8-12 d). From d 6, lysozyme activity decreased to 70 U/mL (d 10). On d 12, amniotic fluid lysozyme activity increased by over 6,000 U/mL compared to d 10. The lysozyme hydrolytic activity was lower in the amniotic fluid (d 8-12) compared to the thick albumen (0-6 d) (P < 0.001). The embryo's protective barriers are changed, and the fractions are hydrated during incubation. It could be concluded that the lysozyme is transferred from the albumen to the amniotic fluid due to its activity.

Unveiling and application of the chicken egg proteome: An overview on a two-decade achievement

Egg proteins are not only the most complete and ideal form of protein for human or embryo nutrition but also play the vital role in the food industry. Egg proteins are subjected to many potential changes under various conditions, which may further alter the nutritional value, physicochemical-properties, and bioactivities of proteins. Recent advances in our understanding of the proteome of raw egg matrix from different species and dynamic changes occurring during storage and incubation are developing rapidly. This review provides a comprehensive overview of the main characteristics of chicken egg proteome, covering all its components and applications under various conditions, such as markers detection, egg quality evaluation, genetic and biological unknown identification, and embryonic nutritional supplementation, which not only contributes to our in-depth understanding of each constituent functionality of proteome, but also provides information to increase the value to egg industry.

Temperature-induced changes in egg white antimicrobial concentrations during pre-incubation do not influence bacterial trans-shell penetration but do affect hatchling phenotype in Mallards

Microbiome formation and assemblage are essential processes influencing proper embryonal and early-life development in neonates. In birds, transmission of microbes from the outer environment into the egg’s interior has been found to shape embryo viability and hatchling phenotype. However, microbial transmission may be affected by egg-white antimicrobial proteins (AMPs), whose concentration and antimicrobial action are temperature-modulated. As both partial incubation and clutch covering with nest-lining feathers during the pre-incubation period can significantly alter temperature conditions acting on eggs, we experimentally investigated the effects of these behavioural mechanisms on concentrations of both the primary and most abundant egg-white AMPs (lysozyme and avidin) using mallard (Anas platyrhychos) eggs. In addition, we assessed whether concentrations of egg-white AMPs altered the probability and intensity of bacterial trans-shell penetration, thereby affecting hatchling morphological traits in vivo. We observed higher concentrations of lysozyme in partially incubated eggs. Clutch covering with nest-lining feathers had no effect on egg-white AMP concentration and we observed no association between concentration of egg-white lysozyme and avidin with either the probability or intensity of bacterial trans-shell penetration. The higher egg-white lysozyme concentration was associated with decreased scaled body mass index of hatchlings. These outcomes demonstrate that incubation prior to clutch completion in precocial birds can alter concentrations of particular egg-white AMPs, though with no effect on bacterial transmission into the egg in vivo. Furthermore, a higher egg white lysozyme concentration compromised hatchling body condition, suggesting a potential growth-regulating role of lysozyme during embryogenesis in precocial birds.

Omics as a Window To Unravel the Dynamic Changes of Egg Components during Chicken Embryonic Development

Chicken egg, as a completely aseptic and self-sufficient biological entity, contains all of the components required for embryonic development. As such, it constitutes not only an excellent model to study the mechanisms of early embryo nutrition and disease origin but can also be used to develop egg-based products with specific applications. Different omics disciplines, like transcriptomics, proteomics, and metabolomics, represent promising approaches to assess nutritional and functional molecules in eggs under development. However, these individual molecules do not act in isolation during the dynamic embryogenic process (e.g., migration, transportation, and absorption). Unless we integrate the information from all of these omics disciplines, there will remain an unbridged gap in the systematic and holistic assessment of the information from one omics level to the other. This integrative review of the dynamic molecular processes of the different chicken egg components involved in embryo development describes the critical interplay between the egg components and their implications in immunity, hematopoiesis, organ formation, and nutrient transport functions during the embryonic process.

Comparative Yolk Proteomic Analysis of Fertilized Low and High Cholesterol Eggs during Embryonic Development

Simple Summary

Cholesterol exists in each cell of the living organism and plays a significant role in cellular functions. Several reports have demonstrated that high yolk cholesterol concentration affected embryo mortality, hatchability, and performance. The present results showed that high-cholesterol egg yolks had increased protein intensities and egg and yolk weight relative to low-cholesterol egg yolks. The differentially expressed yolk proteins were primarily involved in lipid transport, lipid localization, nutrient reservoir function, and embryo protection during embryonic development.

Abstract

The yolk is the principal part of the egg that contains vitamins, minerals, lipids, and proteins which are essential for embryo development and hatching. The egg yolk contains significant amounts of lipoproteins, triacylglycerides, and cholesterol, whose dynamics are indistinct during embryogenesis. The effects of cholesterol on the yolk protein abundance, intensity, and function are ill-defined during embryonic development. Using two-dimensional gel electrophoresis, eggs with respective high and low cholesterol protein abundance were investigated after 0, 2, 6, and 13 days of embryogenesis and further analyzed by matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry. The results revealed that the vitellogenin proteins are the most abundant egg yolk protein that showed proximity and a high degree of variation in isoelectric point and molecular weight. The results demonstrated increased expression of vitellogenin-1 and vitellogenin-3 at two days and vitellogenin-2 protein at 13 days of embryogenesis in both egg types. The ovoinhibitor, immunoglobulin lambda light chain precursor, Ig-gamma (clone-36 chicken), and beta-2-glycoprotein-1 precursor proteins were significantly expressed in high cholesterol eggs while haptoglobin protein PIT-54 and vitelline membrane outer layer proteins intensities were significant in low cholesterol eggs at two days of embryogenesis. The high cholesterol eggs showed a modest increase in egg weight, yolk weight, albumen height, yolk color, and egg strength relative to the low cholesterol eggs. The gene ontology enrichment analysis revealed that the differentially expressed proteins such as vitellogenin proteins were involved in lipid transport and lipid localization biological processes and showed nutrient reservoir activity function. The ovotransferrin regulated the biological processes of plasminogen activation and extracellular matrix disassembly and characterized the anchored component of the plasma membrane. The ovoinhibitor protein was involved in response to mineralocorticoid and corticosterone biological processes whereas the vitellin membrane outer layer protein constituted the extracellular exosome, extracellular organelle, and membrane-bounded vesicle cellular components. Collectively, our study revealed yolk protein abundance, molecular function, cellular components, and biological processes and concluded that yolk protein intensities were significantly altered by cholesterol concentration.

Transcriptome analyses to reveal the dynamic change mechanism of pigeon magnum during one egg-laying cycle

We analyzed the transcriptome of pigeon magnum in three stages (C1: pre-ovulation, C2: post-ovulation, C3: 5-6 days after ovulation) to elucidate the molecular and cellular events associated with morphological changes during the laying cycle. We observed that C1 was highly developed, apoptosis rate was highest in C2, and C3 attained the smallest size. Through RNA-sequencing, we obtained 54,764,938 (97.2%) high-quality clean reads that aligned to 20,767 genes. Gene expression profile analysis showed the greatest difference between C1 and C3; 3966 differentially expressed genes (DEGs) were identified, of which 2250 genes were upregulated and 1716 genes were downregulated in C1. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses revealed that protein processing and transport activities were prominent in C1, and upregulated genes included those related to signal recognition particle (SRP), signal recognition particle receptor (SRPR), translocon, GRP78, RRBP1, TRAP, TRAM1, and OST. Egg white protein-related gene expression was highest, with OVALY being the most highly expressed. In C2, apoptosis-related gene expression was higher than in C1, and fatty acid metabolism was active, which may be correlated with magnum tissue regression. Collagen- and laminin-related gene expression was prominent in C1 and C3, indicating roles in egg white protein generation and magnum reconstruction. PR gene expression was highest and exhibited drastic change in the three groups, indicating that PR and its regulation may be involved in changes in magnum morphology and function. Through the identification and functional analysis of DEGs and other crucial genes, this may contribute to understand the egg white protein production, magnum tissue regression, and magnum regeneration mechanisms.

A Comprehensive Identification of Chicken Egg White Phosphoproteomics Based on a Novel Digestion Approach

There are plenty of phosphoproteins in chicken egg white (CEW), which are of great significance for the biological activity and function of CEW. In this study, phosphorylated proteins in CEW were identified and analyzed based on two digestion strategies (trypsin and trypsin/glutamyl endoproteinase). Besides, the enrichment strategy of immobilized metal affinity chromatography was used, and phosphopeptides were identified by nano liquid chromatography/tandem mass spectrometry. A total of 189 phosphosites mapped onto 166 phosphopeptides corresponding to 96 phosphoproteins were identified. Gene ontology analysis suggested that these phosphoproteins of CEW mainly participated in biological processes such as "cell process", "biological regulation", and "response to stimulus". Moreover, the phosphoproteins of CEW were involved in molecular functions, primarily including "binding" and "catalytic activity". On the basis of the available literature, the research was the first comprehensive identification of chicken egg white phosphoproteins. This study further enriched the identification of phosphoproteins in CEW and laid a foundation for the subsequent study of phosphoproteins.

Interactions between egg storage duration and broiler breeder age on egg fat content, chicken organ weights, and growth performance

Egg storage and breeder age are between the most important factors affecting egg lipids, chicken quality, and posthatch performance. To evaluate these factors, including their interaction, the impact of egg storage duration (5, 12, and 19 D), and breeder age (47 and 67 wk) was investigated in Arbor Acres broiler eggs and chickens. Total yolk fat content, chicken organ development at hatch and at 6 D of age, and posthatch performance (at 7 D and 35 D of age) were determined. Total fat content in fresh yolk was lower in 12 and 19 D stored eggs than in 5 D stored eggs (Δ = −2.42% on average). In hatchlings, the heart percentage was not affected by storage duration in the younger flock but was higher after 19 D than after 5 and 12 D of storage in the old flock (Δ = +0.09% on average). Residual yolk weight was higher after 12 D egg storage than after 5 D egg storage (Δ = +1.7 g), with 19 D egg storage in between. Liver and intestine percentage decreased with storage duration. Residual yolk weight (Δ = +1.09 g) and liver percentage (Δ = +0.18%) were higher in old breeders than in younger breeders. At day 6, chicken BW, yolk free body mass, liver percentage, and intestine percentage interacted between egg storage duration and breeder age with the strongest effects in chickens from older breeder after 19 D of storage. Heart percentage was lower after 19 D compared with 5 and 12 D of storage (Δ = −0.05% on average). Feed intake and feed conversion ratio were higher between day 0 to 7 and 0 to 35 after 19 D than after 5 D egg storage (Δ19-5 D = +12 g and +199 g; +0.11 points and +0.09 points, respectively). It can be concluded that when it is needed, eggs from younger breeders should be stored for a prolonged period (≥12 D) rather than those from older breeders.

Proteomic alteration of albumen by dietary vanadium in commercial egg-type layers

Vanadium (V) is an ultratrace metal with the insulin-tropic properties and is often researched as the diabetes drug. However, in animals, V has been reported to have toxic effects on the development, immunity, oxidation-reduction equilibrium, gastrointestinal function, and so forth. Especially in poultry, supplementation of more than 10 mg of V/kg in the layer diets has been shown to adversely affect the egg production and egg quality. In this study, we supplemented 0 mg of V/kg, 5 mg of V/kg, and 10 mg of V/kg in the layer diets for 35 D and examined the quantitative proteomics of albumen for finding the possible target signaling pathway and mechanism of V action and made the preliminary verification. In contrast to the control group, V resulted in a significant drop in the albumen height, and in oviduct ampulla, the activity of total antioxidant capacity and glutathione peroxidase significantly decreased (P = 0.01, P = 0.02), the content of malonic dialdehyde significantly increased (P = 0.01), and the apoptosis rate significantly increased in the 5-mg V/kg and 10-mg V/kg treatment groups (P ＜ 0.01). V affected 36 differentially accumulated proteins in albumen, with 23 proteins upregulated and 13 proteins downregulated. The expressions of innate protein albumen lysozyme (Q6LEL2), vitellogenin-2 (P02845), and the F1NWD0 protein in albumen belonged to the P53 family were significantly reduced, in contrast to the control (P < 0.05), and the expression of riboflavin-binding protein (P02752) was significantly improved (P < 0.05). The Hippo signaling pathway-fly, which is suitable for the key protein P53 as the most significantly affected network, might be important for discriminating V.

Comparative Quantitative Phosphoproteomic Analysis of the Chicken Egg during Incubation Based on Tandem Mass Tag Labeling

Protein phosphorylation plays an important role in protein structure and function. To investigate the role of egg protein phosphorylation in chicken embryonic development, a comparative and quantitative phosphoproteomic analysis of fertilized chicken egg white and yolk was performed during incubation. Overall, 215 phosphosites mapped onto 205 phosphopeptides corresponding to 100 phosphoproteins were identified. Among these phosphoproteins, 123 phosphosites from 62 egg proteins were found significantly changed (p < 0.05) at day 12 during incubation. Furthermore, GO analysis suggested that these differentially phosphorylated proteins were associated with various molecular functions, primarily including binding, molecular function regulator, and transport activity. Such findings in this study improved our understanding of the protein molecular functions involved in chicken embryonic development from a protein phosphorylation perspective.

Deleterious amino acid substitutions with a series of putative damaging effects on egg components are revealed in the ovalbumin gene family; an in silico approach

This study was conducted to identify the most deleterious nonsynonymous single nucleotide polymorphisms (nsSNPs) in the ovalbumin gene family, including OVALX, OVALY, and OVAL genes, which are involved in the synthesis of the most important components in the chickens’ eggs using a comprehensive in silico approach. Ten different computational servers were utilized to prioritize the possible deleterious effects of the retrieved nsSNPs in terms of structure, function, and stability. Results indicated entirely damaging effects of H365P in OVALX, I167T in OVALY, and V209G, L231P, F307C, and S317P in OVAL proteins. Further prediction tools showed that all of these deleterious nsSNPs were positioned in variable locations within several α-helix motifs in all studied ovalbumin proteins. Furthermore, all witnessed nsSNPs were predicted to be resided in the receptors binding sites, signifying remarkable involvement of such nsSNPs in damaging of the altered proteins. In conclusion, the present study provides the first inclusive data with regard to the most deleterious nsSNPs in OVALX, OVALY and OVAL genes in chickens. The present bioinformatics data may be useful for breeders who intend to raise chickens for egg production, in such a way the presence of any of these deleterious nsSNPs in any selected breed may possess several damaging effects on the egg components, which may impair egg production. Therefore, it can be stated that breeders have to confirm the absence of any of these deleterious nsSNPs before being proceeded further for large-scale egg-production purposes.

Differential proteomic analysis revealed crucial egg white proteins for hatchability of chickens

For healthy development, an avian embryo needs the nutritional and functional molecules maternally deposited in avian eggs. Egg white not only provides nutritional components but also exhibits functional properties, such as defenses against microbial invasion. However, the roles of the more detailed messages in embryo development remain unclear. In this study, a tandem mass tag labeling quantitation approach was used to innovatively identify the differential proteins in the egg whites of fresh eggs produced by hens with divergent high/low hatchability and in the egg whites of embryonated eggs with healthy and dead embryos. A total of 378 proteins were quantified in egg white, which is the most complete proteome identified for egg white to date, and up to 102 differential proteins were identified. GO enrichment, pathway, and hierarchical clustering analysis revealed some of the differential proteins that are the main participants in several biological processes, including blood coagulation, intermediate filament, antibacterial activity, and neurodevelopment. A list of 11 putative protein biomarkers, such as keratin (KRT19, KRT12, KRT15, and KRT6A), which is involved in cell architecture, and fibrinogen (fibrinogen alpha chain, fibrinogen beta chain, and fibrinogen gamma chain), which is related to blood coagulation, were ultimately screened. The current study screened egg white proteins that can predict low hatchability and embryonic death and deciphered the role of these proteins in embryonic development, which is meaningful for the comprehensive understanding of embryonic growth.

Integrated Proteomic and N-Glycoproteomic Analyses of Chicken Egg during Embryonic Development

To better appreciate the alterations of egg proteins and their modifications during embryonic development, a comparative and quantitative study was performed aimed at chicken egg white and yolk proteome and N-glycoproteome after 12 days of incubation using tandem mass tag (TMT)-labeling technology in conjunction with reversed-phase high-performance liquid chromatography (RP-HPLC). A total of 334 unique N-glycosite-containing peptides from 153 N-glycoproteins were identified, of which 82 N-glycosite-containing peptides showed significant changes after 12 days of incubation. The varied proteome was mainly involved with antibacterial, ionic binding, cell proliferation, and embryonic development, while the different degrading and/or absorbing priorities of egg proteins were proposed. This study provides substantial insight into the effects of N-glycoprotein variations on the utilization of egg proteins by chicken embryo during incubation.

Comparative proteomic analysis of hen egg yolk plasma proteins during embryonic development

Avian egg yolk provides essential nutrients and physiological support for the developing embryo. To reveal the dynamics of yolk proteins during the entire period of incubation, we analyzed the alterations of egg yolk plasma proteins at different times during incubation (day 0, 7, 14, and 18). Day 14 (D14) of incubation was considered as the key point on the alteration of egg yolk proteins according to the SDS-PAGE analysis. The two-dimensional electrophoresis-based comparative proteomic analysis was conducted, and 26 spots representing 13 proteins were detected with significant changes in abundance. An accelerating transfer of ovalbumin from egg white into egg yolk was observed at D14 in fertilized eggs but not detected in unfertilized eggs, indicating an unrevealed absorbing pathway for the egg proteins/peptides particularly in fertilized eggs. Meanwhile, the abundance of yolk riboflavin-binding protein constantly decreased after D14, which might meet the need for essential riboflavin during embryo development. PRACTICAL APPLICATIONS: These findings provide fundamental insight into the effects of incubation on egg yolk plasma protein alterations during the entire embryonic development for a better understanding of plasma protein biological functions, especially in nutrient transportations and the formation of embryonic organs.

Non-destructive characterization of egg odor and fertilization status by SPME/GC-MS coupled with electronic nose

BACKGROUND

Early and non-destructive identification of fertile (F) eggs is a difficult task in the process of breeding laying hens. The odors emitted from unfertilized (UF), infertile (IF), and fertile (F) eggs were characterized by solid-phase microextraction / gas chromatograph-mass spectrometry (SPME/GC-MS) and electronic nose (E-nose) to determine their differences by principal component, partial least squares, and canonical discriminant analyses.

RESULTS

A total of 14 volatiles were identified in unhatched shell white Leghorn eggs, such as nonanal, decanal, 6-methyl-5-hepten-2-one, and 6,10-dimethyl-5,9-undecadien-2-one. Cedrene and decanal contributed greatly to the classification of UF and fertilized (Fd)/IF eggs; cedrene, decanal, 1-octanol and hexanal contributed greatly to the distinction between UF and IF eggs; heptanal might be the potential marker to determine F/IF eggs. P40/1, P10/2, P10/1, TA/2, T40/2 and T30/1, P30/1, P40/2, PA/2, T40/2 mostly contributed to the distinction between UF and Fd eggs and between F and IF eggs, respectively. Canonical discriminant analysis presented superior differentiating efficiency for almost all groups, and the odor differences between UF and Fd eggs were significantly larger than the differences between F and IF eggs.

CONCLUSION

Solid-phase microextraction / gas chromatograph-mass spectrometer combined with E-nose may have the potential to non-destructively distinguish UF, F, and IF eggs, which will provide a new perspective to understand the differences among them. © 2018 Society of Chemical Industry.

The Salmonella Enteritidis TolC outer membrane channel is essential for egg white survival

Salmonella Enteritidis has developed the potential to contaminate eggs by surviving in the antimicrobial environment of the hen's egg white. This has led to a worldwide pandemic of foodborne salmonellosis infections in humans due to the consumption of contaminated eggs and egg-derived products. The molecular mechanisms of Salmonella Enteritidis egg white survival are not fully clear. Using in vivo expression technology and promoter-reporter fusions we showed that the promoter of the tolC gene, encoding the TolC outer membrane channel that is used by multidrug efflux pumps to export harmful molecules and to secrete bacterial products, is activated by egg white at the chicken body temperature. Using a Salmonella Enteritidis tolC deletion mutant we showed that TolC has an important role in egg white survival. Chromatographic separation techniques and subsequent testing of antimicrobial activities of separated egg white fractions led to the identification of ovotransferrin as the egg white antimicrobial factor which is capable of inhibiting growth of a tolC deletion strain but not the wild type strain. We provide evidence that TolC protects Salmonella Enteritidis against ovotransferrin-mediated growth inhibition in egg white.

Different incubation patterns affect selective antimicrobial properties of the egg interior: experimental evidence from eggs of precocial and altricial birds

Avian eggs contend with omnipresent microorganisms entering the egg interior, where they affect embryo viability and hatchling phenotype. The incubation behaviour and deposition of egg white antimicrobial proteins (AMPs) vary highly across the avian altricial-precocial spectrum. Experimental evidence of how these alterations in avian reproductive strategies affect the antimicrobial properties of the precocial and altricial egg interior is lacking, however. Here, we tested the egg white antimicrobial activity in eggs of two representative model species, from each end of the avian altricial-precocial spectrum, against potentially pathogenic and beneficial probiotic microorganisms. Eggs were experimentally treated to mimic un-incubated eggs in the nest, partial incubation during the egg-laying period, the onset of full incubation and the increased deposition of two main egg white AMPs, lysozyme and ovotransferrin. We moreover assessed to what extent egg antimicrobial components, egg white pH and AMP concentrations varied as a result of different incubation patterns. Fully incubated precocial and altricial eggs decreased their antimicrobial activity against a potentially pathogenic microorganism, whereas partial incubation significantly enhanced the persistence of a beneficial probiotic microorganism in precocial eggs. These effects were most probably conditioned by temperature-dependent alterations in egg white pH and AMP concentrations. While lysozyme concentration and pH decreased in fully incubated precocial but not altricial eggs, egg white ovotransferrin increased along with the intensity of incubation in both precocial and altricial eggs. This study is the first to experimentally demonstrate that different incubation patterns may have selective antimicrobial potential mediated by species-specific effects on antimicrobial components in the egg white.

Roles of the sire and dam quail in egg, yolk, albumen, and shell weight alterations due to the parthenogenetic trait

Infertile eggs from Chinese Painted quail exhibit parthenogenesis, and the 1st egg in a clutch sequence is more likely to develop a parthenogenetic embryo. Also, hens that exhibit parthenogenesis have shorter clutches and heavier egg weights. These larger eggs may be a result of the egg residing in the oviduct longer, allowing more time for the parthenote to develop. However, it is unknown which components of the egg are altered due to the parthenogenetic trait or the role of dams and sires from the parthenogenetic line of quails in these alterations. Therefore, our objective was to determine if the parthenogenetic trait in dams, sires, or both contributes to alterations in egg components, such as yolk, albumen, and shell weights. Two selected lines of quail, 1 line selected for parthenogenesis and 1 line that was unselected for the parthenogenetic trait (control), were utilized in a 2 x 2 factorial arrangement of dam and sire lines to create 4 breeding treatments: control dams + control sires (CC), control dams + parthenogenetic sires (CP), parthenogenetic dams + control sires (PC), parthenogenetic dams + parthenogenetic sires (PP). Daily, fresh eggs were collected, labeled, weighed, and the germinal disc was classified as fertile, unfertilized without development, or parthenote. Yolk, albumen, and shell weights were obtained, and their weights were also calculated as percentage of total egg weight. A dam main effect revealed heavier weights for total egg, yolk, albumen, and shell as well as a larger percentage of albumen and ratio of albumen to yolk in parthenogenetic line dams versus control line dams. However, the percentage of yolk was higher for control than parthenogenetic line dams. The increase in total egg and egg component weights due to the parthenogenetic trait suggests that the transit time of the egg through the oviduct is altered. Perhaps transit through the magnum and uterus is delayed the most yielding greater albumen and shell weights, respectively.

Identification of N-Glycosites in Chicken Egg White Proteins Using an Omics Strategy

Chicken egg white (CEW) is a perfect source of natural proteins that possesses outstanding functional properties and various bioactivities. The glycosylation structure of CEW proteins plays important roles in their functions, bioactivities, and allergies. The present work attempted to identify N-glycosites of CEW proteins using an omics strategy. CEW proteins were digested with trypsin and chymotrypsin; glycopeptides were enriched and deglycosylated using PNGase F in H₂¹⁸O water, followed by analysis using high-performance liquid chromatography/tandem mass spectrometry (HPLC-MS/MS). A total of 71 N-glycosites in 26 CEW glycoproteins were identified. Web-Logo analysis showed that most of the N-glycosites were at N-X-T (55%) and N-X-S (32%). Furthermore, two-dimensional electrophoresis of CEW clusterin demonstrated a series of spots horizontally distributed at 35-37 kDa with an extremely wide isoelectric point range of 4.54-6.68, indicating the heterogeneity of glycosylation of CEW clusterin. These results provided important information for the understanding of the structures, functions, and bioactivities of CEW glycoproteins.

Arginine prevents thermal aggregation of hen egg white proteins

The control of aggregation and solubilization of hen egg white protein (HEWP) is an important issue for industrial applications of one of the most familiar food protein sources. Here, we investigated the effects of edible amino acids on heat-induced aggregation of HEWP. The addition of 0.6M arginine (Arg) completely suppressed the formation of insoluble aggregates of 1mgmL^-1 HEWP following heat treatment, even at 90°C for 20min. In contrast, lysine (Lys), glycine (Gly), and sodium chloride (NaCl) did little to suppress the aggregation of HEWP under the same conditions. SDS-PAGE indicated that Arg suppresses the thermal aggregation of almost all types of HEWP at 1mgmL^-1. However, Arg did not suppress the thermal aggregation of HEWP at concentrations ≥10mgmL^-1 and prompted the formation of aggregates. Transmission electron micrographs revealed a high-density structure of unfolded proteins in the presence of Arg. These results indicate that Arg exerts a greater suppressive effect on a protein mixture, such as HEWP, than on a single model protein. These observations may propose Arg as a safe and reasonable additive to HEWP for the elimination of microorganisms by allowing an increase in sterilization temperature.

Characterization of egg white antibacterial properties during the first half of incubation: A comparative study between embryonated and unfertilized eggs

Egg white is an important contributor to the protection of eggs against bacterial contaminations during the first half of incubation (day zero to 12), prior to the egg white transfer into the amniotic fluid to be orally absorbed by the embryo. This protective system relies on an arsenal of antimicrobial proteins and on intrinsic physicochemical properties that are generally unfavorable for bacterial multiplication and dissemination. Some changes in these parameters can be observed in egg white during egg storage and incubation. The aim of this work was to characterize changes in the antibacterial potential of egg white in embryonated eggs (FE) during the first half of incubation using unfertilized eggs (UF) as controls. Egg white samples were collected at day zero, 4, 8, and 12 and analyzed for pH, protein concentration, and protein profile. Antibacterial properties of egg white proteins were evaluated against Listeria monocytogenes, Streptococcus uberis, Staphylococcus aureus, Escherichia coli, and Salmonella Enteritidis. During incubation, differential variations of egg white pH and protein concentrations were observed between UF and FE. At equal protein concentrations, similar activities against L. monocytogenes and S. uberis were observed for FE and UF egg white proteins. A progressive decline in these activities, however, was observed over incubation time, regardless of the egg group (UF or FE). SDS-PAGE analysis of egg white proteins during incubation revealed discrete changes in the profile of major proteins, whereas the stability of some less abundant antimicrobial proteins seemed more affected. To conclude, the antibacterial activity of egg white proteins progressively decreased during the first half of egg incubation, possibly resulting from the alteration of specific antimicrobial proteins. This apparent decline may be partly counterbalanced in embryonated eggs by the increase in egg white protein concentration. The antibacterial potential of egg white is very effective during early stages of embryonic development but its alteration during incubation suggests that extra-embryonic structures could then progressively ensure protective functions.

Egg serpins: The chicken and/or the egg dilemma

Twenty-seven serpins belonging to clade A, B, C, D, E, F, G, H and I serpins are currently referenced in chicken genome databases. Phylogenetic analysis of chicken serpins revealed that ovalbumin (Serpinb14) and its paralogs ovalbumin-related protein Y (Serpinb14b) and ovalbumin-related protein X (Serpinb14c) are found in bird species. These clade B serpins are specifically expressed in reproductive tissues and exported in the egg where they constitute major protein components. These data suggest that these three paralogs have probably appeared in birds to face new environments and ensure the extra-uterine development of an embryo in a shell egg. Twelve other serpins have been identified in the newly produced egg, some of them having a specific distribution in the respective egg structures (eggshell, egg white, vitelline membrane and egg yolk). The physiological role of these egg serpins remain largely unexplored, but there is increasing evidence in literature or by homologies with their mammalian counterparts, that some of them participate in cell proliferation, tissue remodeling and/or angiogenesis associated with folliculogenesis and development of extraembryonic structures, eggshell biomineralization, egg defense and nutrition of the embryo. A better knowledge of the phylogenetic evolution of these 15 serpins in other oviparous species, on their egg distribution, on their regulation during embryonic development (activation/degradation/transfer) and on their functional specificity, is needed to better appreciate their role and their bird-specificity. These review shed light on the multiple possibilities that offer the avian egg model to study the role of serpins in reproduction and developmental biology.

Proteome analysis of the almond kernel (Prunus dulcis)

BACKGROUND

Almond (Prunus dulcis) is a popular tree nut worldwide and offers many benefits to human health. However, the importance of almond kernel proteins in the nutrition and function in human health requires further evaluation. The present study presents a systematic evaluation of the proteins in the almond kernel using proteomic analysis.

RESULTS

The nutrient and amino acid content in almond kernels from Xinjiang is similar to that of American varieties; however, Xinjiang varieties have a higher protein content. Two-dimensional electrophoresis analysis demonstrated a wide distribution of molecular weights and isoelectric points of almond kernel proteins. A total of 434 proteins were identified by LC-MS/MS, and most were proteins that were experimentally confirmed for the first time. Gene ontology (GO) analysis of the 434 proteins indicated that proteins involved in primary biological processes including metabolic processes (67.5%), cellular processes (54.1%), and single-organism processes (43.4%), the main molecular function of almond kernel proteins are in catalytic activity (48.0%), binding (45.4%) and structural molecule activity (11.9%), and proteins are primarily distributed in cell (59.9%), organelle (44.9%), and membrane (22.8%).

CONCLUSION

Almond kernel is a source of a wide variety of proteins. This study provides important information contributing to the screening and identification of almond proteins, the understanding of almond protein function, and the development of almond protein products. © 2015 Society of Chemical Industry.

Identification and comparative proteomic study of quail and duck egg white protein using 2-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry analysis

A proteomic study of egg white proteins from 2 major poultry species, namely quail (Coturnix coturnix) and duck (Anas platyrhynchos), was performed with comparison to those of chicken (Gallus gallus) through 2-dimensional polyacrylamide gel electrophoresis (2-DE) analysis. By using matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry (MALDI-TOF MS/MS), 29 protein spots representing 10 different kinds of proteins as well as 17 protein spots designating 9 proteins were successfully identified in quail and duck egg white, respectively. This report suggested a closer relationship between quail and chicken egg white proteome patterns, whereas the duck egg white protein distribution on the 2-DE map was more distinct. In duck egg white, some well-known major proteins, such as ovomucoid, clusterin, extracellular fatty acid-binding protein precursor (ex-FABP), and prostaglandin D2 synthase (PG D2 synthase), were not detected, while two major protein spots identified as “deleted in malignant brain tumors 1” protein (DMBT1) and vitellogenin-2 were found specific to duck in the corresponding range on the 2-DE gel map. These interspecies diversities may be associated with the egg white protein functions in cell defense or regulating/supporting the embryonic development to adapt to the inhabiting environment or reproduction demand during long-term evolution. The findings of this work will give insight into the advantages involved in the application on egg white proteins from various egg sources, which may present novel beneficial properties in the food industry or related to human health.

Thermal aggregation of hen egg white proteins in the presence of salts

Hen egg white contains more than 40 kinds of proteins with concentrations reaching 100 mg/mL. Highly concentrated protein mixtures are common in the food industry, but the effects of a crowded environment containing salts on protein stability and aggregation have only been investigated using pure protein solutions. Here, we investigated the thermal aggregation of hen egg white protein (EWP) at various concentrations in the presence of inorganic salts by solubility measurements and SDS-PAGE. EWP at 1 mg/mL formed aggregates with increasing temperature above 55 °C; the aggregation temperatures increased in the presence of inorganic salt with the Hofmeister series. Namely, the chaotrope 0.5 M NaSCN completely suppressed the thermal aggregation of 1 mg/mL EWP. As the protein concentration increased, NaSCN unexpectedly enhanced the protein aggregation; the aggregation temperature of 10 and 100 mg/mL EWP solutions were dramatically decreased at 62 and 47 °C, respectively. This decrease in aggregation temperatures due to the chaotrope was described by the excluded volume effect, based on a comparative experiment using Ficoll 70 as a neutral crowder. By contrast, the kosmotrope Na2SO4 did not affect the aggregation temperature at concentrations from 1 to 100 mg/mL EWPs. The unexpected fact that a chaotrope rather enhanced the protein aggregation at high concentration provides new insight into the aggregation phenomena with the Hofmeister effect as well as the crude state of highly concentrated proteins.

Mass Spectrometry and Two-Dimensional Electrophoresis To Characterize the Glycosylation of Hen Egg White Ovomacroglobulin

Glycosylation of proteins plays an important role in their biological functions, such as allergenicity. Ovomacroglobulin (OVMG) is a glycoprotein from hen egg white, but few studies have been done so far to delineate the glycosylated sites of OVMG. The present study characterized the glycosylation of OVMG using mass spectrometry and two-dimensional electrophoresis. MALDI-TOF-MS showed that the OVMG subunit [M + H](+) ion has a peak at m/z 183297; therefore, the carbohydrate moiety is calculated as 11.5% of the whole OVMG molecule. HPLC-ESI-MS/MS confirmed that of 13 potential N-glycosylation sites of OVMG, 11 sites were glycosylated; 1 site (N(1221)) was found in both glycosylated and nonglycosylated forms. On the two-dimensional electrophoresis gel, a series of OVMG spots horizontally distributed at 170 kDa, with an isoelectric point range of 5.03-6.03, indicating the heterogeneity of glycosylation of OVMG. These results provided important information for understanding of structure, function, and potential allergenic sites of OVMG.

Effects of experimentally increased in ovo lysozyme on egg hatchability, chicks complement activity, and phenotype in a precocial bird

In birds, spectrum of egg white proteins deposited into the egg during its formation are thought to be essential maternal effects. Particularly, egg white lysozyme (LSM), exhibiting great between and within species variability, is considered to be essential for developing avian embryos due to its physiological, antimicrobial, and innate immune defense functions. However, there have been few studies investigating effects of LSM on early post-hatching phenotype, despite its broad physiological and protective role during embryogenesis. Here, we test how experimentally increased concentrations of egg white LSM affect hatchability in Japanese quail (Coturnix japonica) and chick phenotype immediately after hatching (particularly body weight, tarsus length, plasma LSM concentration, and plasma complement activity). Chicks from eggs with increased LSM concentration displayed reduced tarsus length compared to chicks from control eggs while hatchability, body weight and plasma LSM concentration were unaffected. It is worth noting that no effect of increased in ovo lysozyme on eggs hatchability could be related to pathogen-free environment during artificial incubation of experimental eggs causing minimal pressure on embryo viability. While tangible in vivo mechanisms during avian embryogenesis remain to be tested, our study is the first to document experimentally that egg white LSM appears to have growth-regulation role during embryo development, with possible underlying phenotypic consequences in the early post-hatching period in precocial birds.

The Family Secrets of Avian Egg-Specific Ovalbumin and Its Related Proteins Y and X

The ovalbumin gene family in Gallus gallus is composed of three homologous genes located within a 46 kb locus on chromosome 2: ovalbumin, ovalbumin-related protein Y (OVAY), and ovalbumin-related protein X (OVAX) genes. The expression of these genes in hen oviduct is under estrogen control, but their relative hormonal responsiveness and subsequent protein concentration in egg, is distinctive. Interestingly, all three proteins lack the classical signal peptide for secretion. Ovalbumin, OVAX, and OVAY belong to the serine protease inhibitor (serpin) family whose members share a common tertiary structure. Ovalbumin and OVAX are one of the few members of this family that do not express any protease inhibition activity whereas OVAY has been predicted to be inhibitory, by comparison with the consensus sequence for inhibitory serpins. In contrast to ovalbumin and OVAY, OVAX interacts with heparin, a negatively charged glycosaminoglycan, via a positively charged domain exposed at the surface of the molecule. Ovalbumin is the major egg white protein and might be a source of amino acids for the developing embryo. The physiological function of OVAY is not known, but recent data have revealed a possible role of this protein in early embryonic development. Considering the antibacterial activities of OVAX, this protein might play a role in egg defense. This review sheds light on the expression, biochemistry, and structural specificities of these three highly similar paralogs. It gives new clues in favor of diverging functions, which are likely to have arisen by duplication events from a common ancestral gene.

Differential abundance of egg white proteins in laying hens treated with corticosterone

Stressful environments can affect not only egg production and quality but also gene and protein abundance in the ovary and oviduct in laying hens. The oviductal magnum of laying hens is the organ responsible for the synthesis and secretion of egg white proteins. The objective of this study was to investigate the effects of dietary corticosterone as a stress model on the abundance of proteins in the egg white and of mRNA and proteins in the magnum in laying hens. After a 14-day acclimation, 40 laying hens were divided into two groups which were provided for the next 14 days with either control (Control) or corticosterone (Stress) diet containing at 30 mg/kg. Corticosterone treatment resulted in increased feed intake (P ≤ 0.05) and decreased egg production. Two-dimensional electrophoresis (2DE) with MALDI-TOF/TOF MS/MS using eggs obtained on days 0 and 5 revealed differential abundance of egg white proteins by Stress: transiently expressed in neural precursors (TENP), hemopexin (HPX), IgY-Fcυ3-4, and extracellular fatty acid-binding protein (Ex-FABP) were decreased while ovoinhibitor and ovalbumin-related protein X (OVAX) were increased on days 5 vs 0 (P ≤ 0.05). Expression of mRNAs and proteins was also significantly modulated in the magnum of hens in Stress on day 14 (P ≤ 0.05). In conclusion, the current study provides the first evidence showing that dietary corticosterone modulates protein abundance in the egg white in laying hens, and it suggests that environmental stress can differentially modify expression of egg white proteins in laying hens.

Effect of embryonic development on the chicken egg yolk plasma proteome after 12 days of incubation

To better appreciate the dynamics of yolk proteins during embryonic development, we analyzed the protein quantitative changes occurring in the yolk plasma at the day of lay and after 12 days of incubation, by comparing unfertilized and fertilized chicken eggs. Of the 127 identified proteins, 69 showed relative abundance differences among conditions. Alpha-fetoprotein and two uncharacterized proteins (F1NHB8 and F1NMM2) were identified for the first time in the egg. After 12 days of incubation, five proteins (vitronectin, α-fetoprotein, similar to thrombin, apolipoprotein B, and apovitellenin-1) showed a major increase in relative abundance, whereas 15 proteins showed a significant decrease in the yolks of fertilized eggs. In unfertilized/table eggs, we observed an accumulation of proteins likely to originate from other egg compartments during incubation. This study provides basic knowledge on the utilization of egg yolk proteins by the embryo and gives some insight into how storage can affect egg quality.