Genetic selection and molecular analysis of domesticated rainbow trout for enhanced growth on alternative diet sources

Abstract

Real-time polymerase chain reaction was used to monitor the expression of specific genes and confirm that an alteration in level of expression correlates with changes in diet, metabolism, or immune response. To test these probe and primer sets for their ability to monitor changes in gene expression, groups of fish were experimentally challenged either via daylength, vitamin availability, or with pathogenic microorganisms. The probes and primers sets were then used to analyze expression levels of specific gene products from isolated RNA. The expression of certain genes such as myosin in muscle correlated significantly with protein intake and seasonal daylength. Other genes involved with growth and metabolism such as insulin-like growth factor and pyruvate kinase showed lower levels of significance in correlating with planes of nutrition and varied with diet and treatment. However differences for pyruvate kinase were found in early tests done with animals receiving a vitamin-reduced diet. For factors relating immunological status after infection with microbiological pathogens, several factors such as MX-1 and CD-8 correlated with dose of the viral pathogen infectious hematopoeitic necrosis virus. Association of pathogen dose with immunological expression level was much less pronounced when fish were tested with bacterial microorganisms. This work will aid in evaluating the effects of diet on fish health and nutrient utilization and for evaluating the effects of selection of trout strains.