Identification of critical sex-biased genes in Andrias davidianus by de novo transcriptome

The Chinese giant salamander Andrias davidianus is a protected amphibian with high nutritional and economic value. Understanding its sex determination mechanism is important for improving culture techniques and sex control in breeding. However, little information on the characterization of critical genes involved in sex is available. Herein, sequencing of ovary and test produced 40,783,222 and 46,128,902 raw reads, respectively, which were jointly assembled into 80,497 unigenes. Of these, 36,609 unigenes were annotated, of which 8907 were female-biased and 10,385 were male-biased. Several sex-related pathways were observed, including the Wnt signaling pathway. After elevated temperature and estrogen exposure, neomale and neofemale specimens were identified by a female-specific marker for the first time. RT-qPCR analysis showed the expression profile of ten selected sex-biased genes to be exhibited consistently in male and neomale and in female and neofemale, with the exception of the Amh and TfIIIa genes. Results suggested that these genes may play important roles in A. davidianus sex determination and gonad development. This provides a basis for further investigation of the molecular mechanisms of sex determination in amphibians.