Location: Office of The Director2012 Annual Report
1a. Objectives (from AD-416):
The main problems in yellow perch culture are the lack of genetically defined broodstock with enhanced traits for year-round production, poor larval survival, slow growth, and disease susceptibility. These problems are being pursued via a long-term genetic selection program to produce superior germplasm and complementary studies to understand the physiological basis for performance traits of interest. This project aims to integrate genetic, molecular, physiological, and nutritional approaches to develop superior pathogen-free broodstocks and improved production methods for commercial industry. We will focus on the following objectives: Objective 1: Develop yellow perch broodstock, define growth and viral hemorrhagic septicemia (VHS)-resistant phenotypes, characterize genetic diversity, and evaluate genotype x environment interaction for growth. Objective 2: Characterize critical pathways involved in growth and VHS resistance in yellow perch through gene expression and physiological studies. Objective 3: Improve early survival and methods for producing feed-trained fingerlings. Objective 4: Develop and evaluate challenge assays, detection tools, and vaccines for protecting yellow perch and other Great Lakes region species of fish from VHS.
1b. Approach (from AD-416):
For objective 1, we will characterize important phenotypes and genotypes in yellow perch broodstocks. Third-generation progeny will undergo performance testing for improved growth and survival and decreased susceptibility to the viral hemorrhagic septicemia (VHS) virus. This will involve evaluation of genotype x environment interactions in laboratory and industrial settings. This information will provide estimates for the heritability of desired traits (growth and VHS resistance) and a better understanding of the sources of phenotypic variation for these traits. For objective 2, we will generate genomic resources to aid in development of molecular tools to genotype and quantify expression of genes involved with growth and immunity in yellow perch. We will also develop proteomic tools that will enable us to measure and characterize the function of critical proteins (hormones and immune markers) important to growth and immunity for this species. Genomic tools will come from next-generation sequencing efforts to characterize the transcriptomes (expressed genes) of key tissues involved with growth and immunity. Proteomic tools will be developed to characterize biochemical pathways that underlie growth and immunity in yellow perch. Lastly, in vitro methods will be used to characterize how viral proteins impact cellular antiviral recognition and response pathways that impact how yellow perch combat VHS infection, and how the virus might evade or suppress immune pathways in this species. For objective 3, we will evaluate and test use of larval specialty micro-diets (SMD) as substitutes for live-prey diets to improve larval survival and standardize and reduce overall costs of producing high-quality yellow perch fingerlings. We will evaluate performance measures (first-feeding, swim bladder inflation, development, survival and growth) of genetically defined larval perch broodstock progeny that are reared under either a control live-diet regimen (typical for industry) or a dietary regimen where live prey is progressively substituted with SMD. For objective 4, we will utilize a standardized VHS challenge model to characterize the disease process and susceptibility of perch broodstocks to VHS infection. We will also develop new diagnostic tools to detect VHS and use these detection tools to evaluate how vaccines and vaccination strategies increase protective immunity against VHS infection. For the challenge assay, genetically defined perch will be exposed to varying doses of VHS virus, and survivors will be re-infected with VHS to characterize resistance and protective immunity to this pathogen. To detect this pathogen, we will develop and validate a novel polymerase chain reaction (PCR) assay that reliably speeds up VHS detection in a cost-effective manner. For vaccination and vaccination strategies, we will characterize protective immunity in perch, evaluating the efficacy and duration of existing and new vaccines for VHS and how new and existing adjuvants extend the efficacy of these vaccines.
3. Progress Report:
Progress was made on all four objectives. We continued to produce and evaluate improved yellow perch broodstocks. Performance trials of the third generation (F3) progeny were completed, and the highest performing individuals were selected, tagged, and are being cycled to enable reproduction in 2013. Genotype by Environment (GxE) studies were completed at two commercial facilities, and data on growth and survival and genetic material were collected at these sites. Cross by strain tests for susceptibility of F3 progeny to the viral hemorrhagic septicemia virus (VHSv) have shown strain-specific differences in survival to pathogen exposure. A non-lethal method for identifying gender in yellow perch was developed. This method was transferred to a major yellow perch producer, enabling this producer to cost-effectively sort sexes for broodstock management and development. We continued to characterize critical pathways that underlie growth, immunity, and susceptibility to the VHSv pathogen, and recently demonstrated that the immune response differs between male (higher) and female (lower) yellow perch following exposure to a pathogen mimetic. Given the higher growth and apparent resistance to pathogen challenge in female perch, development of all-female broodstocks may improve production of perch in commercial aquaculture. Research is underway to develop and test diets that sustain high growth and immunity in genetically-improved yellow perch; this research will address suspected nutritional deficiencies that cause skeletal abnormalities and disease in rapidly growing perch. Research is demonstrating that various structural genes of the VHSv contribute to its virulence in fish cell-lines, whereas another specific gene stimulates the innate immune response in fish cell-lines. The stimulating effect of this VHSv structural gene on the innate immune system suggests it can be used as an adjuvant to boost immune performance in vaccines. We continued to develop and test methods that improve early survival and feed training of yellow perch fingerlings. Improvements to early feeding and rearing resulted in higher egg survival from each egg strand, meaning that reproductive success was improved. Findings are also enabling refinements to live feeds that will further improve survival of larval yellow perch. Development of a rapid test for detecting VHSv in yellow perch was completed. The standardized reverse transcriptase polymerase chain reaction (StaRT-PCR) shows high specificity to the VHSv and displays higher dynamic range in quantifying virus levels and lower false positive and false negative events than present assays. The progress resulting from this research should impact efforts to select yellow perch broodstocks with high growth and low susceptibility to the VHS virus, improve reproductive performance and fingerling quality for yellow perch producers, facilitate the development and testing of vaccines that minimize the effects of the VHS virus, and enable cost-effective surveillance and detection of the VHS virus in agricultural and fisheries production settings.
Shepherd, B.S., Rees, C.B., Binkowski, F., Goetz, F. 2012. Characterization and evaluation of sex-specific expression of suppressors of cytokine signaling (SOCS) -1 and -3 in juvenile yellow perch (Perca flavescens) treated with lipopolysaccharide. Fish and Shellfish Immunology. 33:468-481.