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

Genetic improvement for faster growth is a conventional approach to increase growth rates in 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 a rainbow trout line selectively bred for fast growth (Growth Line, GL) and a contemporary 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 characterize differences in gene expression profiles between populations. 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 (GH/IGF) and PI3K-Akt, JAK-STAT, MAPK, and cAMP signal transduction pathways. A greater concentration of plasma IGF-I was detected in the GL compared to SC (p < 0.05). 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 variation in growth performance in selectively bred rainbow trout.针对快速生长的遗传改良是提升水产养殖物种生长速率的常规手段，但目前尚未完全阐明调控鱼类生长表现的遗传与生理因子。本研究旨在通过对比同一选育项目中，快速生长选育虹鳟品系（Growth Line, GL）与同期随机交配对照品系（Synthetic Control, SC）的肝脏及肌肉转录组（transcriptome），解析与快速生长相关的生理机制。本研究同时纳入了来自商业卵供应商的第三个遗传品系（Commercial A, CA），以解析不同种群间的基因表达谱差异。收获时，GL组的体质量分别较SC组与CA组高出约20%与8%（p < 0.05）。GL与SC组的肝脏及白肌中分别存在145个和36个差异表达基因（differentially expressed genes, DEG），这些基因显著富集于生长激素/胰岛素样生长因子轴（growth hormone/ insulin-like growth factor axis, GH/IGF）及PI3K-Akt、JAK-STAT、MAPK、cAMP等信号转导通路。GL组的血浆胰岛素样生长因子I（IGF-I）浓度显著高于SC组（p < 0.05）。CA组呈现独特的基因表达谱，其肝脏与白肌中分别存在11个和210个差异表达基因，这些基因与先天免疫、补体系统及代谢通路相关。综上，本研究结果更为全面地解析了鱼类快速生长表型，进一步阐明了选育虹鳟生长表现遗传变异的生理基础。