Transcriptomic and epigenomic alterations of Nile tilapia gonads sexually reversed by high temperature

Tilapia males are favored by the farming industry due to faster growing and higher body weights in a given period than females, and increasing the male proportion is desired for breeding. Previous studies indicate that high temperature treatment could sporadically transform genetic females of Nile tilapia to become phenotypic males, while the mechanism is unclear. Here, we treated female Nile tilapia with high temperature at early developmental stage, and obtained sex reversed pseudo-male (i.e. masculinized female) fish with morphologically male gonads. Transcriptome sequencing and whole genome methylation analyses were performed on gonads from normal males, females and pseudo-males. The profiles of gene expression and CpG methylation were compared. The results suggested that pseudo-males exhibited strikingly similar gene expression and methylation patterns with genetic males, but highly distinct from females. The differentially expressed genes between pseudo-males and other groups revealed a possibility that alterations in the potassium ion transportation processes might play important roles in sex reversal of female tilapia upon high temperature treatment. Our study provided a landscape of global gene expression and methylation status in the heat induced masculinized pseudo-male tilapia.