Comparative transcriptome analysis reveals PERP upregulated during Salmonella Enteritidis challenge in laying ducks

Flaxseed Supplementation in Chicken Feed Accelerates Salmonella enterica subsp. enterica Serovar Enteritidis Clearance, Modulates Cecum Microbiota, and Influences Ovarian Gene Expression in Laying Hens

Salmonella is a foodborne pathogen that poses a serious threat to both human and animal health and food safety. Flaxseed is rich in unsaturated fatty acids; has anti-metabolic syndrome, anti-inflammatory, and neuroprotective properties; and may be a potential source of feed additives. To investigate the impact of flaxseed on Salmonella-infected laying hens, we administered Salmonella enterica subsp. enterica serovar Enteritidis (S. Enteritidis) after adding flaxseed to the feed of laying hens (15% [750 mg/kg]). S. Enteritidis colonization was reduced and its clearance was accelerated from the laying hens. Furthermore, flaxseed supplementation mitigated the damage to the ileum caused by S. Enteritidis. We analyzed alterations in intestinal flora through 16S rRNA amplicon sequencing. S. Enteritidis infection increased the abundance of Akkermansia and triggered the host inflammatory response. Conversely, the addition of flaxseed to the feed increased the abundance of beneficial intestinal bacteria, such as Lactobacilli and Bacteroides. Ovarian health is important for egg production performance in laying hens and our findings indicate that S. Enteritidis can persist in the ovaries for an extended period. Therefore, we further performed transcriptome sequencing analysis of ovarian tissues on day seven after S. Enteritidis infection. S. Enteritidis infection leads to altered ovarian gene expression, including the downregulation of lipid metabolism and growth and development genes and the upregulation of host immune response genes in laying hens. The upregulation of genes associated with growth and development may have stimulated ovarian growth and development.

Molecular characterisation and function analysis of NOD1 gene from Yangzhou goose (Anser cygnoides domesticus)

1. NOD1 is a significant member of the NOD-like receptor (NLR) family. Its main role is to identify microorganisms that invade the body, transmit immune signals and regulate innate immune responses. However, the expression and role of the NOD1 in immune defence against infection in geese remain unknown.2. The RT-PCR method and rapid amplification of cDNA ends (RACE) was used to obtain the full-length goose NOD1 (gNOD1) cDNA series. The cDNA for gNOD1 contains 2856-bp nucleotides, i.e. 47-bp 5' UTR, 135-bp 3' UTR, and 1275-bp ORF region, and encodes a 951-amino-acids (AAs) polypeptide chain. The nucleotide sequence of gNOD1 was found more than 90% similar to its homologs from other avian organisms.3. The qRT-PCR results showed that gNOD1 mRNA was widely distributed in different tissues, but highly expressed in liver, spleen, lung and caecum tissues.4. Following stimulation of goose embryo fibroblasts (GEFs) with lipopolysaccharide (LPS) and polyriboinosinic polyribocytidylic acid (poly(I:C)), the expression of gNOD1 and cytokines, such as IL-1β, IL-6, IL-18, and TNF-α, changed with the response-efficacy correlation at 24 and 48 h post-infection (hpi).5. When the goslings were challenged with Salmonella entertidis (SE) and LPS, the expression of gNOD1 was up-regulated at 3 and 6 hpi in the spleen and caecum tissues, respectively. However, after SE infection, the expression level of gNOD1 fluctuated, while in the LPS group, gNOD1 mRNA increased immediately at a peak time of 6 hpi and then steadily declined. These results indicated that NOD1 was associated with the potency to resist bacterial and viral infections in the goose, both in vivo and in vitro.

Dual Transcriptomic Analyses Unveil Host-Pathogen Interactions Between Salmonella enterica Serovar Enteritidis and Laying Ducks (Anas platyrhynchos)

Salmonella enteritidis (SE) is a pathogen that can readily infect ovarian tissues and colonize the granulosa cell layer such that it can be transmitted via eggs from infected poultry to humans in whom it can cause food poisoning. Ducks are an important egg-laying species that are susceptible to SE infection, yet the host–pathogen interactions between SE and ducks have not been thoroughly studied to date. Herein, we performed dual RNA-sequencing analyses of these two organisms in a time-resolved infection model of duck granulosa cells (dGCs) by SE. In total, 10,510 genes were significantly differentially expressed in host dGCs, and 265 genes were differentially expressed in SE over the course of infection. These differentially expressed genes (DEGs) of dGCs were enriched in the cytokine–cytokine receptor interaction pathway via KEGG analyses, and the DEGs in SE were enriched in the two-component system, bacterial secretion system, and metabolism of pathogen factors pathways as determined. A subsequent weighted gene co-expression network analysis revealed that the cytokine–cytokine receptor interaction pathway is mostly enriched at 6 h post-infection (hpi). Moreover, a number of pathogenic factors identified in the pathogen–host interaction database (PHI-base) are upregulated in SE, including genes encoding the pathogenicity island/component, type III secretion, and regulators of systemic infection. Furthermore, an intracellular network associated with the regulation of SE infection in ducks was constructed, and 16 cytokine response-related dGCs DEGs (including IL15, CD40, and CCR7) and 17 pathogenesis-related factors (including sseL, ompR, and fliC) were identified, respectively. Overall, these results not only offer new insights into the mechanisms underlying host–pathogen interactions between SE and ducks, but they may also aid in the selection of potential targets for antimicrobial drug development.

Identification of Differentially Expressed Non-coding RNA Networks With Potential Immunoregulatory Roles During Salmonella Enteritidis Infection in Ducks

Salmonella enterica serovar Enteritidis (S. Enteritidis) is a pathogen that can colonize the preovulatory follicles of poultry, thereby causing both reduced egg production and an elevated risk of foodborne salmonellosis in humans. Although a few studies have revealed S. Enteritidis preferentially invades the granulosa cell layer within these follicles, it can readily persist and proliferate through mechanisms that are not well-understood. In this study, we characterized competing endogenous RNA (ceRNA) regulatory networks within duck granulosa cells following time-course of S. Enteritidis challenge. The 8108 long non-coding RNAs (lncRNAs), 1545 circular RNAs (circRNAs), 542 microRNAs (miRNAs), and 4137 mRNAs (fold change ≥2; P < 0.01) were differentially expressed during S. Enteritidis challenge. Also, eight mRNAs, eight lncRNAs and five circRNAs were selected and the consistent expression trend was found between qRT-PCR detection and RNA-seq. Moreover, the target genes of these differentially expressed ncRNAs (including lncRNAs, circRNAs and miRNAs) were predicted, and significantly enriched in the innate immune response and steroidogenesis pathways. Then, the colocalization and coexpression analyses were conducted to investigate relationships between ncRNAs and mRNAs. The 16 differentially expressed miRNAs targeting 60 differentially expressed mRNAs were identified in granulosa cells at 3 and 6 h post-infection (hpi) and enriched in the MAPK, GnRH, cytokine-cytokine receptor interaction, Toll-like receptor, endocytosis, and oxidative phosphorylation signaling pathways. Additionally, underlying lncRNA-miRNA-mRNA and circRNA-miRNA-mRNA ceRNA networks were then constructed to further understand their interaction during S. Enteritidis infection. Lnc_012227 and novel_circ_0004892 were identified as ceRNAs, which could compete with miR-let-7g-5p and thereby indirectly modulating map3k8 expression to control S. Enteritidis infection. Together, our data thus identified promising candidate ncRNAs responsible for regulating S. Enteritidis infection in the preovulatory follicles of ducks, offering new insights regarding the ovarian transmission of this pathogen.

Screening and identification of SipC-interacting proteins in Salmonella enteritidis using Gal4 yeast two-hybrid system in duck

The zoonotic pathogen Salmonella not only reduces the production performance in ducks, but also poses a serious threat to human health through eggs and pollutes water bodies through feces. SipC, an effector protein of type III secretion systems (T3SS) in Salmonella, mediates translocation of effectors into the eukaryotic host. However, the precise role of SipC effectors remains unknown in ducks. In this study, the SipC from duck granulosa cells (dGCs) was selected as bait, and the SipC-interacting proteins in Salmonella enteritidis (SE) were screened using Gal4 yeast two-hybrid system in duck. Twelve SipC-interacting proteins were identified. Among those, the p53-effector related to PMP-22 (PERP) and TGF-β activated kinase 1-binding protein 2 (TAB2) were selected to further confirm the function by GST pull-down in vitro. Over-expression of PERP resulted in not only increasing SE adhesion and invasion but also triggering the production of IL-1β and IFN-α in SE infected dGCs, while knock-down PERP showed the opposite tendency (P < 0.01). In addition, TAB2 significantly induced the production of IL-6, IL-1β, IFN-α, and INF-γ in SE infected dGCs (P < 0.05), but did not cause obvious changes in SE adhesion and invasion. When the sipC in SE was deleted, the activities of duck PERP and TAB2 were abolished because they could not bind to SipC. Taken together, although the protein of PERP and TAB2 can interact with SipC, their mechanisms were different in duck challenged by SE. Therefore, PERP was involved in SE invasion and inflammatory response of dGC ovaries, and TAB2 only contributed to dGCs inflammatory response, which provided critical insights about the mechanism in host- bacterium protein interactions during Salmonella invasion in duck.