Transcriptomic Response of the Ovarian Follicle Complex in Post-Vitellogenic Rainbow Trout to 17α,20β-Dihdroxy-4-pregnen-3-one In Vitro.

Gonadotropins and progestins are the primary regulators of follicle maturation and ovulation in fish, and they require complex communication among the oocyte and somatic cells of the follicle. The major progestin and the maturation-inducing hormone in salmonids is 17α,20β-dihdroxy-4-pregnen-3-one (17,20βP), and traditional nuclear receptors and membrane steroid receptors for the progestin have been identified within the follicle. Herein, RNA-seq was used to conduct a comprehensive survey of changes in gene expression throughout the intact follicle in response to in vitro treatment with these hormones to provide a foundation for understanding the coordination of their actions in regulating follicle maturation and preparation for ovulation.

Remodeling of the epigenetic landscape in rainbow trout, Oncorhynchus mykiss, offspring in response to maternal choline intake.

This project focused on evaluating the effects of maternal dietary choline intake on global DNA methylation profiles and related transcriptional changes in rainbow trout offspring. Three experimental diets were formulated to test different levels of choline intake: (a) 2065 ppm choline (Low Choline, 0 % supplementation), (b) 5657 ppm choline (Medium Choline, 0.6 % supplementation), and (c) 9248 ppm choline (High Choline, 1.

Profiling growth performance, insulin-like growth factors, and IGF-binding proteins in rainbow trout lacking IGFBP-2b.

Insulin-like growth factor-binding proteins (IGFBPs) regulate insulin-like growth factor (IGF) signaling, but IGFBP-specific functions are not well characterized in fishes. A line of rainbow trout () lacking a functional IGFBP-2b was produced using gene editing and subsequent breeding to an F2 generation. This loss-of-function model [IGFBP-2b knockout (2bKO)] was subjected to either continuous feeding or feed deprivation (3 wk) followed by refeeding (1 wk).

The Impact of Exposure Dosage and Host Genetics on the Shedding Kinetics of Flavobacterium psychrophilum in Rainbow Trout.

Flavobacterium psychrophilum, the causative agent of bacterial cold water disease (BCWD), is one of the leading pathogens in rainbow trout (Oncorhynchus mykiss) aquaculture. To date, there is little knowledge of the transmission kinetics of F. psychrophilum over the course of infection.

Direct actions of growth hormone in rainbow trout, Oncorhynchus mykiss, skeletal muscle cells in vitro.

The growth hormone (GH)-insulin-like growth factor-1 (IGF-1) system regulates skeletal muscle growth and function. GH has a major function of targeting the liver to regulate IGF-1 production and release, and IGF-1 mediates the primary anabolic action of GH on growth. However, skeletal muscle is a target tissue of GH as evidenced by dynamic GH receptor expression, but it is unclear if GH elicits any direct actions on extrahepatic tissues as it is difficult to distinguish the effects of IGF-1 from GH.

Accurate genotype imputation from low-coverage whole-genome sequencing data of rainbow trout.

With the rapid and significant cost reduction of next-generation sequencing, low-coverage whole-genome sequencing (lcWGS), followed by genotype imputation, is becoming a cost-effective alternative to single-nucleotide polymorphism (SNP)-array genotyping. The objectives of this study were 2-fold: (1) construct a haplotype reference panel for genotype imputation from lcWGS data in rainbow trout (Oncorhynchus mykiss); and (2) evaluate the concordance between imputed genotypes and SNP-array genotypes in 2 breeding populations. Medium-coverage (12×) whole-genome sequences were obtained from a total of 410 fish representing 5 breeding populations with various spawning dates.

Discovery and Genomic Characterization of a Novel Hepadnavirus from Asymptomatic Anadromous Alewife ().

The alewife ( is an anadromous herring that inhabits waters of northeastern North America. This prey species is a critical forage for piscivorous birds, mammals, and fishes in estuarine and oceanic ecosystems. During a discovery project tailored to identify potentially emerging pathogens of this species, we obtained the full genome of a novel hepadnavirus (ApHBV) from clinically normal alewives collected from the Maurice River, Great Egg Harbor River, and Delaware River in New Jersey, USA during 2015-2018.

Genome-wide association analysis of the resistance to infectious hematopoietic necrosis virus in two rainbow trout aquaculture lines confirms oligogenic architecture with several moderate effect quantitative trait loci.

Infectious hematopoietic necrosis (IHN) is a disease of salmonid fish that is caused by the IHN virus (IHNV), which can cause substantial mortality and economic losses in rainbow trout aquaculture and fisheries enhancement hatchery programs. In a previous study on a commercial rainbow trout breeding line that has undergone selection, we found that genetic resistance to IHNV is controlled by the oligogenic inheritance of several moderate and many small effect quantitative trait loci (QTL). Here we used genome wide association analyses in two different commercial aquaculture lines that were naïve to previous exposure to IHNV to determine whether QTL were shared across lines, and to investigate whether there were major effect loci that were still segregating in the naïve lines.

Structural and genetic basis for the binding of a mouse monoclonal antibody to Flavobacterium psychrophilum lipopolysaccharide.

A mouse monoclonal antibody (mAb FL100A) previously prepared against Flavobacterium psychrophilum (Fp) CSF259-93 has now been examined for binding to lipopolysaccharides (LPS) of this strain and Fp 950106-1/1. The corresponding O-polysaccharides (O-PS) of these strains are formed by identical trisaccharide repeats composed of l-Rhamnose (l-Rha), 2-acetamido-2-deoxy-l-fucose (l-FucNAc) and 2-acetamido-4-R-2,4-dideoxy-d-quinovose (d-Qui2NAc4NR) where R represents a dihydroxyhexanamido moiety. The O-PS loci of these strains are also identical except for the gene (wzy1 or wzy2) that encodes the polysaccharide polymerase.

Gliding motility proteins GldJ and SprB contribute to virulence.

causes columnaris disease in fish. Columnaris disease is incompletely understood, and adequate control measures are lacking. The type IX secretion system (T9SS) is required for gliding motility and virulence.

Maternal dietary choline levels cause transcriptome shift due to genotype-by-diet interactions in rainbow trout (Oncorhynchus mykiss).

The objective of this study was to identify metabolic regulatory mechanisms affected by choline availability in rainbow trout (Oncorhynchus mykiss) broodstock diets associated with increased offspring growth performance. Three customized diets were formulated to have different levels of choline: (a) 0 % choline supplementation (Low Choline: 2065 ppm choline), (b) 0.6 % choline supplementation (Medium Choline: 5657 ppm choline), and (c) 1.

Complete genome sequence of a novel papillomavirus in Siamese fighting fish () from Trinidad and Tobago.

Here, we announce the complete genome of a previously undescribed papillomavirus from a betta fish, . The genome is 5,671 bp with a GC content of 38.2%.

Fecal Microbiome Analysis Distinguishes Bacterial Taxa Biomarkers Associated with Red Fillet Color in Rainbow Trout.

The characteristic reddish-pink fillet color of rainbow trout is an important marketing trait. The gastrointestinal microbiome is vital for host health, immunity, and nutrient balance. Host genetics play a crucial role in determining the gut microbiome, and the host-microbiome interaction impacts the host's phenotypic expression.

Plasma proteomic profiling of bacterial cold water disease-resistant and -susceptible rainbow trout lines and biomarker discovery.

Genetic variation for disease resistance is present in salmonid fish; however, the molecular basis is poorly understood, and biomarkers of disease susceptibility/resistance are unavailable. Previously, we selected a line of rainbow trout for high survival following standardized challenge with (), the causative agent of bacterial cold water disease. The resistant line (ARS-Fp-R) exhibits over 60 percentage points higher survival compared to a reference susceptible line (ARS-Fp-S).

RNA-Seq analysis of the pyloric caecum, liver, and muscle reveals molecular mechanisms regulating fillet color in rainbow trout.

Background: The characteristic pink-reddish color in the salmonids fillet is an important, appealing quality trait for consumers and producers. The color results from diet supplementation with carotenoids, which accounts for up to 20-30% of the feed cost. Pigment retention in the muscle is a highly variable phenotype.

The generation of the first chromosome-level de novo genome assembly and the development and validation of a 50K SNP array for the St. John River aquaculture strain of North American Atlantic salmon.

Atlantic salmon (Salmo salar) in Northeastern US and Eastern Canada has high economic value for the sport fishing and aquaculture industries. Large differences exist between the genomes of Atlantic salmon of European origin and North American (N.A.

Secreted peptidases contribute to virulence of fish pathogen .

causes columnaris disease in freshwater fish in both natural and aquaculture settings. This disease is often lethal, especially when fish population density is high, and control options such as vaccines are limited. The type IX secretion system (T9SS) is required for virulence, but secreted virulence factors have not been fully identified.

Genomic selection models substantially improve the accuracy of genetic merit predictions for fillet yield and body weight in rainbow trout using a multi-trait model and multi-generation progeny testing.

Background: In aquaculture, the proportion of edible meat (FY = fillet yield) is of major economic importance, and breeding animals of superior genetic merit for this trait can improve efficiency and profitability. Achieving genetic gains for fillet yield is possible using a pedigree-based best linear unbiased prediction (PBLUP) model with direct and indirect selection. To investigate the feasibility of using genomic selection (GS) to improve FY and body weight (BW) in rainbow trout, the prediction accuracy of GS models was compared to that of PBLUP.

ferric iron uptake systems are required for virulence.

, which causes columnaris disease, is one of the costliest pathogens in the freshwater fish-farming industry. The virulence mechanisms of are not well understood and current methods to control columnaris outbreaks are inadequate. Iron is an essential nutrient needed for metabolic processes and is often required for bacterial virulence.

A large-scale, multi-year microbial community survey of a freshwater trout aquaculture facility.

Aquaculture is an important tool for solving the growing worldwide food demand, but infectious diseases of farmed animals represent a serious roadblock to continued industry growth. Therefore, it is essential to understand the microbial communities that reside within the built environments of aquaculture facilities to identify reservoirs of bacterial pathogens and potential correlations between commensal species and specific disease agents. Here, we present the results from 3 years of sampling a commercial rainbow trout aquaculture facility.

Siderophores Produced by the Fish Pathogen Flavobacterium columnare Strain MS-FC-4 Are Not Essential for Its Virulence.

Flavobacterium columnare causes columnaris disease in wild and aquaculture-reared freshwater fish. F. columnare virulence mechanisms are not well understood, and current methods to control columnaris disease are inadequate.

Weighted Single-Step GWAS Identifies Genes Influencing Fillet Color in Rainbow Trout.

The visual appearance of the fish fillet is a significant determinant of consumers' purchase decisions. Depending on the rainbow trout diet, a uniform bright white or reddish/pink fillet color is desirable. Factors affecting fillet color are complex, ranging from the ability of live fish to accumulate carotenoids in the muscle to preharvest environmental conditions, early postmortem muscle metabolism, and storage conditions.

Identification of Haplotypes Associated With Resistance to Bacterial Cold Water Disease in Rainbow Trout Using Whole-Genome Resequencing.

Bacterial cold water disease (BCWD) is an important disease in rainbow trout aquaculture. Previously, we have identified and validated two major QTL (quantitative trait loci) for BCWD resistance, located on chromosomes Omy08 and Omy25, in the odd-year Troutlodge May spawning population. We also demonstrated that marker-assisted selection (MAS) for BCWD resistance using the favorable haplotypes associated with the two major QTL is feasible.

Leptin Receptor Deficiency Results in Hyperphagia and Increased Fatty Acid Mobilization during Fasting in Rainbow Trout ().

Leptin is a pleiotropic hormone known for regulating appetite and metabolism. To characterize the role of leptin signaling in rainbow trout, we used CRISPR/Cas9 genome editing to disrupt the leptin receptor (LepR) genes, and . We compared wildtype (WT) and mutant fish that were either fed to satiation or feed deprived for six weeks.

Evidence for a leptin-insulin axis in a fish, the tilapia (Oreochromis mossambicus).

Leptin, insulin, and glucagon are involved in regulating glycaemia in vertebrates and play a role in the progression of obesity and type 2 diabetes. While mammals possess an 'adipoinsular axis' whereby insulin stimulates leptin release from adipocytes and leptin in turn feeds back on the pancreas to inhibit further insulin secretion, evidence of such an axis in non-mammalian vertebrates is unknown. We investigated the interactions between these glycaemic hormones and provide evidence for a leptin-insulin axis in a teleost fish, the tilapia.