Ploidy effects on genes regulating growth mechanisms during fasting and refeeding in juvenile rainbow trout (Oncorhynchus mykiss)

Authors: Cleveland, Beth; Weber, Gregory - Greg

Submitted to: Molecular and Cellular Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/18/2013
Publication Date: 1/25/2014
Publication URL: http://handle.nal.usda.gov/10113/58239
Citation: Cleveland, B.M., Weber, G.M. 2014. Ploidy effects on genes regulating growth mechanisms during fasting and refeeding in juvenile rainbow trout (Oncorhynchus mykiss). Molecular and Cellular Endocrinology. 382(1): 139-149.

Interpretive Summary: Production of triploid (three sets of chromosomes instead of two) fish is a valuable technology in the aquaculture industry, with sterility in triploid females being the trait of most value. With three sets of chromosomes, the triploid nuclei are 50% larger than diploid (two sets of chromosomes) nuclei, so triploid cells are generally larger than diploid cells, often with consequences such as reduced surface area to volume ratios. Therefore, understanding how triploidy alters the regulation of genes affecting growth and nutrient partitioning provides insights into how physiological mechanisms differ with polyploidy. During feed deprivation at this early age diploids mobilize visceral nutrient stores more than triploids, and during refeeding triploids increase carcass growth rates faster than diploids. Differences in kinetics of gene expression between diploids and triploids and between liver and muscle may contribute to improved recovery growth in triploids. These results indicate that regulation of physiological mechanisms in response to feed deprivation and refeeding differ between early juvenile diploid and triploid rainbow trout, and that each ploidy may exhibit optimal growth and nutrient retention under different feeding strategies or diet formulations that exploit these mechanisms.

Technical Abstract: Diploid and triploid rainbow trout weighing approximately 3 g were either fed for five weeks, or feed deprived for one week, followed by refeeding. During feed deprivation the diploids mobilized visceral stores to a greater extent than the triploids, and during refeeding, carcass growth rate recovered more quickly in the triploids than in the diploids. Liver ghr2 and igfbp2b expression increased and igfbp1b decreased in fasted fish. The extent to which genes were regulated during feed deprivation and refeeding was also affected by ploidy, with a gene dosage effect evident as a greater capacity for up-regulation and down-regulation in the diploids and triploids, respectively. Mechanisms for improved recovery growth in triploids include decreased hepatic igfbp expression, differences in TGFbeta ligand signaling through tgfbr and smad expression, and variations in expression of muscle regulatory factors. These data suggest effects of polyploidy on physiological and endocrine mechanisms regulating growth and nutrient partitioning.