In this study, the researchers sequenced and assembled the genomes of one male (ZZ) and one female (ZW) tongue sole, respectively. Based on the difference of sequencing depth of Z/W linked-scaffolds between female and male, together with the high-resolution genetic map constructed by SSR and SNP, they assembled the Z and W chromosome of tongue sole at high quality. Using the Z-W homologous genes, they estimated that the age of the tongue sole sex chromosome pair is relatively young (about 30 million years), which contrasts with the age of hundreds of millions of years for the mammalian and avian sex chromosomes. Interestingly, researchers found that the sex chromosomes of tongue sole are derived from the same ancestral vertebrate protochromosome as the avian W and Z chromosomes. Furthermore, the same gene on the Z chromosome, dmrt1, which is the male-determining gene in birds, showed convergent evolution of features that are compatible with a similar function in tongue sole.
To understanding the regulatory mechanisms involved in the temperature-dependent sex reversal as well as the inheritance of sex reversal in tongue sole, researchers then analyzed the gonadal DNA methylomes and transcriptomes of normal males (ZZ), pseudo-males (ZW), normal females (ZW), and the offspring of a pseudo-male crossed with a female. They found that, after phenotypic sexual reversal, the genome-wide methylation patterns of genetic females have been accurately shaped to the patterns of normal males. Furthermore, the methylation changes after sex reversal were enriched in genes in the sex determination pathway. By comparing parental and offspring samples, researchers also found that the methylation changes between parental pseudo-males and females were inherited by offspring pseudo-males, probably explaining why the offspring genetic females of pseudo-males can undergo sexual reversal without temp
|Contact: Jia Liu|