Abstract
Leptin is a multifunctional protein involved in processes such as body weight regulation, energy expenditure, fat metabolism, food intake, and appetite regulation. Duplicate leptin genes, leptin-a and leptin-b, were previously detected in the orange-spotted grouper. In this study, we cloned the full-length open reading frame (ORF) of the leptin-a gene in the orange-spotted grouper, searched for polymorphisms, and performed association analyses between these polymorphisms and seven growth traits. Six polymorphisms, consisting of 2 SNPs in intron 1 (c.182T > G, c.183G > T) and 4 SNPs in exon 2 (c.339C > G, c.345C > T, c.447G > A, c.531C > T), were identified and genotyped in 200 individuals. The c.182T > G and c.183G > T polymorphisms showed complete linkage and were analyzed together. Association analyses revealed that the c.182 + 183TG > GT polymorphism was significantly associated with body weight (BWT) and body width (BWH), with the AB (TG/GT) genotype showing positive effects on growth traits. Additionally, the SNP c.447G > A was significantly associated with BWT, BWH, overall length (OL), trunk width (TW), and head length (HL), with the GA genotype displaying positive effects on growth traits. The c.531C > T SNP showed a close association between the TT genotype and decreased growth. Our results demonstrate that several polymorphisms in the leptin-a gene are associated with growth traits and can be used for marker-assisted selection (MAS) in orange-spotted grouper populations.
Highlights
The orange-spotted grouper (Epinephelus coioides) belongs to the subfamily Epinephelinae and mainly inhabits the Indian Ocean, the Red Sea, the Mediterranean Sea, the NorthernPacific Ocean, the Western Pacific Ocean and Southeast Asia [1,2]
Heterozygous mutational genotypes were detected for the 6 single nucleotide polymorphisms (SNPs), but recessive homozygosis mutational genotype was only detected for the c.531C > T SNP (Table 1)
Our results revealed that the mutation c.182 + 183TG > GT is highly associated with growth traits of the orange-spotted grouper and that the AB (TG/GT) genotype positively affects such growth traits
Summary
Pacific Ocean, the Western Pacific Ocean and Southeast Asia [1,2]. It is a highly valued cultured marine species and is farmed in many countries including China, Thailand, Singapore, Japan, Indonesia, and Brunei Darussalam [3]. According to FAO fishery statistics, the global aquaculture production value of the orange-spotted grouper has increased by almost 100-fold from 1999 to 2009, from 33,000 to. In China, the orange-spotted grouper has become a major food fish in live fish markets and is an important cultured fish for commercial sale in the Guangdong, Hainan, Taiwan and Fujian provinces. The vast market demands for orange-spotted grouper have driven efforts to breed families and populations with higher growth rates and lower food coefficients. The application of marker-assisted selection (MAS) to the orange-spotted grouper is a promising strategy for improving growth traits, and the identification of genetic markers associated with growth traits could contribute to genetic improvements in cultured fishes and advance the MAS process
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