Abstract
BackgroundFish body color is one of the major factors that determine the commercial value of farmed fish, to understand for coloration mechanisms. The expression of melanin-related genes is according to the developmental stage and light intensity in the red spotted grouper, Epinephelus akaara.MethodsTo investigate changes in melanin formation and melanin-related genes in the larval development stage, fish larvae were reared from fertilized egg stage to 50 days after hatching (DAH). Experiment of body color changes was performed under each different light intensity conditions. Melanin-related genes expression was analyzed by real-time qPCR, and body coloration difference was represented by RGB (red, green, blue) code value.ResultsExpression levels of melanin-concentrating hormone (MCH) mRNA, pro-opiomelanocortin (POMC) mRNA, and melanocortin 1 receptor (MC1R) mRNA were at their highest 5 DAH (days after hatching). Expression levels of agouti-signaling protein (ASIP) mRNA were at their highest 10 DAH. Results of body color changes according to changes in light intensity conditions showed that the expression level of MCH mRNA in the 2000 lx group was the highest at 6 weeks. The expression levels of POMC mRNA and MC1R mRNA in the 1000 lx group were at their lowest at 9 weeks. RGB color code value under different light intensities were the brightest under 1000 lx and the darkest under 0 lx.ConclusionOur research suggests that POMC mRNA and MC1R mRNA in the red spotted grouper are involved in melanin synthesis, and these genes are thought to be controlled by light intensity. To better understand the molecular mechanism of coloration in the red spotted grouper, further studies are needed to clarify the relationship between melanophore development and melanin-related genes.
Highlights
Melanin is one of the major decision factors about hair and body color in vertebrate including human (Fujii 2000)
MC4R is involved in obesity and priapism, and MC5R is involved in immune regulation, separation of red blood cells, and the maintenance of homeostasis. α-MSH stimulates the synthesis of melanin from melanocytes by revitalizing melanocortin 1 receptor (MC1R)
Melanin-concentrating hormone (MCH) mRNA expression was significantly higher than the other tissues in the diencephalon (P < 0.05) (Fig. 1a)
Summary
Melanin is one of the major decision factors about hair and body color in vertebrate including human (Fujii 2000). It is synthesized in the melanosomes of melanocytes and affects skin and body color. Melanin in fish has numerous functions including, among others, skin protection, pigmentation, immunity, and stress responses (Amiya et al 2008; Kittilsen et al 2009; Sköld et al 2013; Cal et al 2017). MC1R is involved in melanin synthesis and body color. Α-MSH stimulates the synthesis of melanin from melanocytes by revitalizing MC1R The expression of melanin-related genes is according to the developmental stage and light intensity in the red spotted grouper, Epinephelus akaara
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