The Role of the Heat Shock Cognate Protein 70 Genes in Sex Determination and Differentiation of Chinese Tongue Sole ( Cynoglossus semilaevis ).

Fish sex determination can be affected by environmental temperature. This process relies on temperature-sensitive proteins such as heat shock proteins (HSPs). Our previous work found that heat shock cognate proteins (HSCs) may participate in high-temperature associated sex reversal of Chinese tongue sole ( Cynoglossus semilaevis ). However, the role of hsc genes in responding to high temperature and affecting sex determination/differentiation remains unclear. Here, by using C. semilaevis as model, we identified hsc70 and hsc70-like . hsc70 was abundant in the gonads with a testicular-higher expression at all gonadal development stages except for 6 months post fertilization (mpf). Intriguingly, hsc70-like showed higher expression in testes from 6 mpf on. Both long-term heat treatment during the temperature-sensitive sex-determining period and short-term heat stress at the end of this period caused different expression of hsc70 / hsc70-like between sexes. The dual-luciferase assay results also suggested that these genes can respond to high temperature rapidly in vitro . Heat treatment of C. semilaevis testis cells overexpressed with hsc70 / hsc70-like could affect the expression of sex-related genes sox9a and cyp19a1a . Our results indicated that hsc70 and hsc70-like were key regulators linking external high-temperature signals with sex differentiation in vivo and provide a new idea for understanding the mechanism by which high temperature affects sex determination/differentiation in teleosts.