Identification of Three Pomca Genotypes in Largemouth Bass (Micropterus Salmoides) and Their Differential Physiological Response to Feed Domestication

Abstract

Diverse feeding habits in teleost are closely related to food intake, involving a wide range of appetite regulating factors. As an appetite-suppressing gene, the polymorphisms of POMCa in largemouth bass (Micropterus salmoides) were validated via direct sequencing and HRM detection, frequency distribution of POMC genotypes were analyzed in two populations fed on different diets, and physiological response to fasting and refeeding were investigated in different genotypes domesticated by formulated diet. 1,828 bp of POMCa cDNA sequence in largemouth bass was amplified and predicted to encode a protein of 218 amino acids which possess the core motifs of POMC gene family. The insertion/deletion of an 18 bp AU-rich element in the 3’ UTR and 4 interlocked SNP loci in the ORF of POMCa were identified in largemouth bass and constitute three genotypes of POMC-A I, II and III, respectively. POMC-A I and Allele I had an increased frequency distribution in the selection population than in the non-selection population, and the proportion of POMC-A Ⅰ in the largest individuals was much greater than that in the smallest individuals of the selection population, while there were a lesser proportion of POMC-A Ⅲ in the largest individuals than that in the smallest individuals (P < 0.05). POMC-A I possessed the lowest value of POMCa mRNA during fasting in feed domestication (P < 0.05), and exhibited growth and physiological advantages according to the levels of body mass and four physiological indicators (i.e., Cor, GH, IGF-1 and Glu) under food deprivation and refeeding. Domestication of largemouth bass by formulated diet in replace of forage fish has been well developed in aquaculture industry in China, and the random inheritance of allele frequency might be affected by decades of selection on feeding traits of largemouth bass. This research would benefit the molecular marker-assisted breeding of largemouth bass that are prone to be domesticated by alternative feed, or better adapted to feeding on formulated diet.

Keywords: Largemouth bass, Proopiomelanocortin (POMC), Genotypes, Fasting and refeeding, Physiological response