Temporal and spatial expression of DMO and DMT gene in Oreochromis aurea

The DMRT genes constitute a new gene family related to sex determination.Like the double-sex gene of Drosophila melanogaster and the mab-3 gene of Caenorhabditis elegents,they encode transcription factors characterized by a conserved zinc-finger like DNA-binding motif,the DM domain,which is thought to bind DNA in the process of sex differentiation and development.In 1998,DMRT1 genes were first identified and found containing DM domain in Homo sapiens and Mus musculus.And DMRT1 was found to regulate sex determination and differentiation in vertebrates extensively.So far,the DMRT genes have been discovered in a wide range of animal species,such as fish,amphibian,reptiles,birds,and mammals.These evidently reveal the evolutionary conservation of DMRT gene family.Tilapia is the most important breeding fish throughout the world.As to Oreochromis aurea,sex is an important economic character,for the male is bigger than the female.So to clarify the mechanism of Oreochromis aurea sex determination will be of great importance in both theory and application.With the hope of doing further research on the function of DMRT genes and clarifying the molecular mechanism of Oreochromis aurea,Real-time Quantitative RT-PCR was used in this research to analyze the temporal and spatial expression patterns on the basis of DMO and DMT gene sequences obtained.Their transcripts appeared from early gastrulae stage during embryonic development,and maintained a considerable high level till the one day's fry,but level of DMO was higher than that of DMT.With the increase of age,the levels of DMO discovered in ovary and brain and DMT only observed in testis both improve.During sex differentiation,after treatment with hormone for 30 days,level of DMO in estrogen group is significantly higher than that in control group(P0.05),while level of DMO in Hydroxyandrostenedione group,aromatase Ⅰand aromataseⅡare remarkably lower than those in control group(P0.05);levels of DMO in all test groups are similar and lower than those in control group,but there are no significant differences among them(P0.05);level of DMT in estrogen group is significantly lower than that in control group(P0.05),while levels of DMT in Hydroxyandrostenedione group and aromatase Ⅱ group are higher than those in control group and level in aromatase Ⅰis lower,but the differences are insignificant(P0.05);DMT can not be detected in brain in all test groups.These results indicate that treatment with hormone can change level of DMO and DMT during sex differentiation,implicating that they could be related with hormone regulation.Moreover,treatment with hormone can evidently improve the male or female ratio of Oreochromis aurea.No DMO and DMT transcripts were found in liver,kidney,spleen,heart and muscle,but unequal amount of DMO transcripts can be detected in brains tissues of mature female and male Oreochromis aurea and the level of DMO in female is remarkably higher than that in male,which suggests that DMO expression is specific in central nervous system(CNS).In addition,we also found the abundant transcripts of DMO in ovary and DMT in testis.This supports that the DMO and DMT genes play important roles not only on the sex determination,but also on the development processes of early embryogenesis.Based on these results,it suggests that DMO should play a key role in CNS and ovary development of Oreochromis aurea and DMT in testis.