1.Key Laboratory of Tropical and Subtropical Fishery Resources Application and Cultivation,Ministry of Agriculture and Rural Affairs,Pearl River Fisheries Research Institute,Chinese Academy of Fishery Sciences,Guangzhou 510380,China;2.College of Fisheries and Life Science,Shanghai Ocean University,Shanghai 201306,China
Abstract: In order to explore the role of Foxl2 gene (forkhead transcription factor gene 2)in gonadal development in blotched snakehead Channamaculata,the Foxl2 gene was cloned by qRT-PCR and RACE (rapid amplification of cDNA ends)techniques in this study.The expression levels of Foxl2 qRT-PCR were detected in different adult tissues including gill,liver,spleen,intestine,middle kidney,muscle,head kidney,ovary,testis,heart,hypothalamus,and brain of XX female and XY male individuals and in the developmental stages of gonads.The expression changes were also analyzed in Foxl2 in gonads of female and male blotched snakehead exposed to exogenous sex hormone treatment (17α-ethynylestradio (EE2)and 17α-methyltestosterone (MT)),and the total contents of serum estrogen (E)were determined in males and females at developmental stages by ELISA.Furthermore,the cell types that Foxl2 protein were expressed in the gonads were detected by immunohistochemistry.The results showed that the full-length cDNA sequence of Foxl2 was found to be 1 939 bp,including 921 bp open reading frame(ORF),encoding 306 amino acids.Tissue expression analysis revealed that the maximal expression levels of Foxl2 was observed in ovaries of 105 d old blotch snakehead post hatching,with significantly different Foxl2 expression levels in ovaries and testis (P<0.01).There was higher expression of Foxl2 in gills and brain in male than that in female individuals (P<0.05).During gonadal development,the transcription of Foxl2 were higher in ovaries than that in testis,with the maximal Foxl2 levels in ovaries of 105 d blotch snakehead post hatching,and with the minimal in testis at that time (P<0.01).The total contents of serum estrogen were similar to the Foxl2 expression during gonadal development.Immunohistochemical detection showed that Foxl2 protein was expressed in granulosa cells around mature oocytes of ovaries,and no signal was detected in testis in blotch snakehead.The expression of Foxl2 was inhibited in ovaries of blotch snakehead exposed to exogenous sex steroid hormone EE2 and MT,but the up-regulated expression level in testis exposed to EE2 and down-regulated expression level in testis exposed to MT.The findings indicated that Foxl2 had obvious sexual dimorphism in the gonads of blotch snakehead,suggesting that Foxl2 be involved in the development and maintenance of ovary.The exogenous sex hormone treatment indicated that Foxl2 was responsive for the regulation of sex steroid hormones.The Foxl2 played an important role in gonadal development of blotch snakehead from mRNA and protein levels,which laid a foundation for the further understanding of the mechanism of sex differentiation and provided a scientific basis for the sex control technology of blotch snakehead.
2022, Vol. 37 
