Study On Gonadal Differentiation Of Chinese Alligator At Different Stages Of Embryonic Development Based On Transcriptome

The way of sex determination in alligators is the temperature-dependent sex determination(TSD).But,the molecular mechanisms of TSD are still not fully understood now since it was first founded.In this paper,Gonad-adrenal-mesonephros(GAM)from the Chinese alligator(Alligator sinensis)embryos incubated in FPT(female producing temperature)and MPT(male producing temperature)were collected at 6 embryonic stages,analyzed by histochemical analysis and transcriptome sequencing subsequently.By analyzing the morphologic changes and expression profiles of the gonad at 6 developmental stages of embryo incubated in FPT and MPT,We studied the molecular mechanisms related to TSD,the exact time that the Chinese alligator determined its sex,and some genes,metabolic pathways related to sex determination.The morphologic changes of gonad at 6 developmental stages of embryo incubated in FPT and MPT showed that females and males were mainly produced at 29 ? and 34 ? respectively.The differences of morphologic changes of females and males were most significant between embryonic day 31 to 41 and day 31 to 36 respectively.RNA-seq yielded 1,150,314,298 clean reads.The number of differentially expressed genes of gonad at adjacent developmental stages in FPT and MPT were 178 and 1268 respectively,and 1785 between FPT and MPT at the same developmental stage.The expression profiles of gonad at 6 developmental stages of embryo incubated in FPT and MPT indicated that there were the greatest differences between males and females at embryonic day 36 and day 41,and genes related to sex determination and differentiation were appeared in these two developmental stages.By analysing morphologic changes and expression profiles of gonad at 6 developmental stages of embryo at FPT and MPT,we concluded that the sex determination time of female and male Chinese alligators may between embryonic day 31 to 41 and day 31 to 36 respectively,and the TSP in the Chinese alligator may between embryonic day 31 to 41.We screened many genes which were related to sex determination,In addition to the genes that have been extensively studied in vertebrates,like SOX9,NR5A1(SF-1),AMH we also screened important genes like RNF17,FOXI1,JARID2,DDX17 and SAFB1.There are some genes related to steroid hormone biosynthesis and members of HSP family.We screened a metabolic pathway related to sex determination and differentiation,steroid hormone biosynthesis.This paper provided the basis for studying the molecular mechanism of Chinese alligator TSD in the future.