Weighted Gene Co-Expression Network Analysis of red body color formation of crimson snapper, Lutjanus erythropterus

Abstract

Crimson snapper (Lutjanus erythropterus) is a highly valued economic fish species, with its red body color being a crucial economic characteristic. A systematic study of skin pigmentation could offer insights into the mechanism of red coloration. In this study, we conducted the first network analysis of snapper transcriptomes during key developmental stages of pigmentation, identifying a cascade of cellular development and responsive gene modules and key genes, including eight developmental-specific modules. Among the four candidate hub genes (TNNT2, ROBO2, APBA2, and APOD), APOD was involved in pigmentation development. The network further revealed some key genes, such as TYRP1a, TYRP1b, PMEL, BCO1, BCO2, CYP2J2, CYP2J6, CYP3A4, PNPLA2, FABP6, ENPP7, and FFAR3, associated with melanin synthesis, carotenoids, and lipid metabolism. Our findings showed that pteridine and carotenoids were involved in yellow coloration after initial feeding, while yellow pigmentation-related genes (e.g., GCH1, PTS, SPR, CBR1, SCARB1, CD36, ABCA1, NpC1L1, etc.) had the same expression pattern at three days post-hatching (3 dph). At the red coloration emergence stage (45 dph), we observed an RNA level signal indicating the conversion of coloring substances from pteridine to carotenoids. These results substantially enhance understanding of the molecular mechanisms underlying pigmentation and skin color variation in L. erythropterus, providing a theoretical basis for improving of body coloration in economically cultured fish and genetic breeding of ornamental fish.