Genome‐wide identification and transcriptome‐based expression profiling of the Sox gene family in the spinyhead croaker ( Collichthys lucidus )

Sox genes encode transcription factors with a high-mobility group (HMG) box, playing critical roles in the initiation and maintenance of a variety of developmental processes, such as sex determination and differentiation. In the present study, we identified 26 Sox genes in the genome of spinyhead croaker Collichthys lucidus (Richardson, 1844) with homology-based analysis of the HMG box. The transcriptome-based expression profiles revealed that the expression of the Sox gene in gonads began to differ between sexes when the body length was 2.74 ± 0.24 cm. At that time, three Sox genes (Sox11b, Sox8a and Sox19) were significantly upregulated, accompanied by the downregulation of 12 Sox genes in the ovary, and six Sox genes were temporarily significantly upregulated in the testis. Afterwards, the expression profile of Sox genes changed only with a small amplitude in both the ovary and testis. For adult tissues, huge differences were observed in the expression profiles of Sox genes between ovaries and testes, as well as small differences in somatic tissues between sexes. These results provide clues to further decipher the role of Sox genes in the processes of sex determination and differentiation in spinyhead croaker and other teleosts.