Maternal Dietary Choline Levels Cause Transcriptome Shift due to Genotype-by-Diet Interaction 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) 1.2% choline supplementation (High Choline: 9248 ppm choline). Six all-female rainbow trout families were fed experimental diets beginning 18 months post-hatch until spawning; their offspring were fed a commercial diet. Experimental broodstock diet did not affect overall choline, fatty acid, or amino acid content in the oocytes (p > 0.05), apart from tyrosine (p = 0.05). Offspring body weights from the High and Low Choline diets did not differ from those in the Medium Choline diet (p > 0.05); however, family-by-diet and sire-by-diet interactions on offspring growth were detected (p = 0.05). The High Choline diet did not improve growth performance in the six broodstock families at final harvest (520-days post-hatch, or dph). Numerous genes associated with muscle development and lipid metabolism were identified, including myosin, troponin C, and fatty acid binding proteins, which were associated with key signaling pathways of lipid metabolism, muscle cell development, muscle cell proliferation, and muscle cell differentiation. These findings indicate that supplementing broodstock diets with choline does regulate expression of genes related to growth and nutrient partitioning but does not lead to growth benefits in rainbow trout families selected for disease resistance. Overall design: To identify metabolic regulatory mechanisms affected by choline availability in rainbow trout broodstock diets associated with improved offspring growth performance, we fed one of three commercial diets formulated with different levels of choline: Low (2065 ppm choline), Medium (5657 ppm choline), and High (9248 ppm choline). We then performed gene expressin profiling analysis using data obtained from RNA-seq of 18 rainbow trout sac-fry at 0-days post-hatch (dph) and 14-dph. Gene expression profiling analysis of RNA-seq data for sac-fry through a main effect of diet and diet-by-broodstock family interaction.