Expression analysis of TYR and DCT genes related to body color in Cynoglossus semilaevis at different periods and in different tissues

Abstract:

Melanin commonly exists in animal tissues. The animal body surface has different colors and abundant pigment patterns due to differences in the distribution and development of melanin and related cells. Different pigment patterns have important functions such as biological camouflage, courtship, etc., especially in fish. Cynoglossus semilaevis, one of the dominant aquaculture flatfish species in China, often suffers from two body color anomalies, i.e. melanism and albinism, which have hindered the development of high-quality seeds and aquaculture. In this study, cDNA sequences of two color-related genes (i.e. TYR and DCT) were cloned and phylogenetically analyzed. Further, expression levels of both genes were analyzed in different stages and in different tissues. The cDNA sequence length of TYR gene coding region is 1620 bp, encoding 539 amino acids. The length of the cDNA sequence in the coding region of DCT gene is 1551 bp, encoding 516 amino acids. In this study, it was found that the expression levels of TYR and DCT were high in fry that were less than 20-day-old, especially during the critical period of metamorphosis (15 to 20-day-old), and decreased to a very low level at 30-day-old. In other skin tissues, the expression levels of these two genes were highest in normal skin on the ocular side and in dark skin on the blind side, and extremely low in albino skin on the ocular side and in normal skin on the blind side. Among other tissues at other times, the highest expression was in the eye, followed by the liver, with very low expression in the spleen and muscles. Results show that TYR and DCT genes are the key genes for blind-side melanogenesis and ocular-side color maintenance in C. semilaevis. This study provides an important basis and reference for identifying the mechanism of color anomaly in C. semilaevis.