Transcriptomic response to selective breeding for fast growth in rainbow trout (Oncorhynchus mykiss)

Authors: Cleveland, Beth; Gao, Guangtu; Leeds, Timothy - Tim

Submitted to: Marine Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/2020
Publication Date: 5/26/2020
Citation: Cleveland, B.M., Gao, G., Leeds, T.D. 2020. Transcriptomic response to selective breeding for fast growth in rainbow trout (Oncorhynchus mykiss). Marine Biotechnology. https://doi.org/10.1007/s10126-020-09974-3.
DOI: https://doi.org/10.1007/s10126-020-09974-3

Interpretive Summary: Fast growth is a performance trait desired by US rainbow trout producers. To support the need for faster growing fish, scientists at the National Center for Cool and Cold Water Research used selective breeding to produce a line of rainbow trout, called the Growth Line, that grows approximately 20% faster than a Control Line. This study identified differences in the gene expression profile between the two lines; these findings are valuable to 1) characterize physiological mechanisms responsible for regulating growth, 2) determine additional mechanisms indirectly affected by genetic selection for improved growth, and 3) identify novel biomarkers valuable for improving breeding efficiency. Results indicated differential regulation of endocrine mechanisms and intracellular signaling pathways that play critical roles in signal transduction and promote muscle and bone growth. These findings provide a more extensive understanding of the mechanistic basis of fast growth in rainbow trout that, in combination with information on genomic variation, contributes to development of novel breeding strategies to establish superior genetics.

Technical Abstract: Genetic improvement for faster growth is a conventional approach to increase growth rates aquaculture species, however the genetic and physiological factors regulating growth performance in fish are not fully characterized. The objective of this study was to identify physiological mechanisms associated with faster growth rates by comparing the liver and muscle transcriptome of rainbow trout bred for fast growth (Growth Line, GL) and a second randomly mated control line (Synthetic Control, SC) from the same selective breeding program. A third genetic line from a commercial egg supplier (Commercial A, CA) was also included to determine whether breeding programs displayed unique gene expression profiles. Body weight of the GL at harvest was approximately 20% and 8% heavier (p < 0.05) than SC and CA, respectively. There were 145 and 36 differentially expressed genes (DEG) in liver and white muscle, respectively, between the GL and SC that were enriched for the growth hormone/ insulin-like growth factor axis and PI3K-Akt, JAK-STAT, MAPK, and cAMP signal transduction pathways. A unique gene profile was detected in CA, with 11 and 210 DEG in liver and white muscle; these genes associated with innate immunity, complement systems, and metabolic pathways. Collectively, these findings provide a more extensive characterization of the fast-growth phenotype in fish that furthers knowledge of the physiological basis for genetic variations in growth performance in selectively bred rainbow trout.