Genome-Wide Identification and Characterization of gh/prl/sl Family in Cynoglossus semilaevis.

The Chinese tongue sole (Cynoglossus semilaevis) is a marine flatfish of significant economic value, characterized by pronounced female-biased sexual size dimorphism (SSD). Sexual differences of cell number and gene expression within the PIT-1 lineage of the pituitary gland may be crucial for interpreting the female-biased SSD of C. semilaevis. Among hormones secreted by PIT-1 cell lineage, growth hormone (gh), prolactin (prl), prolactin 2 (prl2), and somatolactin (sl) comprise a gene family within the extensive superfamily of class-1 helical cytokines. To better understand the function of the gh/prl/sl in teleost SSD, we firstly identified five genes of the gh/prl/sl family (gh, sl, prl, prl2a, and prl2b) and their receptors (ghra, ghrb, prlra, prlrb, and prlr-like) from C. semilaevis at the genome-wide level. Phylogenetic analyses revealed that the gh/prl/sl family and their receptors were each clustered into five distinct groups. More microsatellites were revealed in the intron 2 of gh gene of female rather than the male and pseudo-male individuals, which is positively correlated with its sexual expression pattern. Interaction network prediction indicated that gh, prl, and sl may collectively contribute to individual growth and development. A FRET experiment showed that ghra can act as a receptor for sl. Additionally, the transcripts of the gh/prl/sl family and their receptors exhibited varying abundances in the pituitary, brain, gonad, and liver of both female and male C. semilaevis, with most ligands showing the highest abundance in the female pituitary. Furthermore, gh and sl were found to be maternally expressed. The knock-down of gh, prl, and sl in the pituitary cells could lead to the expression change of igf1, c-fos, and sos2. This study provided a foundation for further functional characterization of the gh/prl/sl gene family, contributing to a deeper understanding of the growth and reproductive mechanisms in C. semilaevis.