| Ovarian hypoplasia is one of the important factors that limite the development of Portunus trituberculatus pond farming,which may be related to reproductive endocrine regulation.Estradiol is the main activite estrogen of crustaceans,but its regulatory mechanism during ovarian development is unclear.In this study,we evaluated the effects of E2 and TAM on ovarian development and expressions of the ovarian development related genes.The specific research results were as follows,these findings could provide basic data for further study on regulate mechanism of estrogen in crustaceans.1.Effects of estrogen on ovarian development and expression of related genes to ovarian development of Portunus trituberculatus in different vitellogenic stagesVitellogenesis of Portunus trituberculatus is divided into two phases,respectively,endogenous vitellogenic stage and exogenous vitellogenic stage.Therefore,this study evaluated the effects of exogenous E2 on ovarian development during these two vitellogenic stage respectively by in vivo experiment with E2 injection and detected expressions of the ovarian development related genes of exogenous vitellogenic stage Portunus trituberculatus through q RT-PCR.The results that exogenous E2 injection dramatically enhanced the estrogen content in the hemolymph of two vitellogenic stage Portunus trituberculatus.Exogenous E2 could significantly increase the GSI of endogenous vitellogenic stage Portunus trituberculatus,but had no significant effect on survival rate and HIS.To exogenous vitellogenic stage,exogenous E2 had no significant influence on the survival rate,GSI and HIS.The q RT-PCR data indicated that the transcripts of vitellogenin(Vg)gene enhanced by exogenous E2 in ovary and in hepatopancreas of experimental crabs during two vitellogenic stages.To endogenous vitellogenic stage,in ovary,hepatopancreas and the cerebral ganglion,E2 inhibited ERR transcriptions.In eyestalk and mandibular organ,E2 obviously enhanced ERR-m RNA levels.To exogenous vitellogenic stage,no significant difference was existed on the ERR expression levels in ovary,hepatopancreas,cerebral ganglion and mandibular organ,while ERR-m RNA level was induced significantly by E2 in the eyestalk.In conclusion,these results suggested that exogenous E2 can significantly improve the ovarian development of endogenous vitellogenic stage Portunus trituberculatus,after the swimming crab growing to exogenous vitellogenic stage,due to the enough reserve of endogenous estrogen,the ovarian development was not under the stimulating effect of exogenous E2.E2 might regulate the ovarian development of crustaceans by promoting Vg gene expression,and possibly affect the other hormone secretion by ERR gene expression in eyestalk and mandibular organ.2.Effects of estrogen antagonist on ovarian development and expression of related genes to ovarian development of Portunus trituberculatusEstrogen plays an important role during the regulation of ovarian development in crustaceans,and tamoxifen(TAM)is a commonly used estrogen antagonist for the studying of molecular mechanism between estrogen and ovarian development of crustacean.This study was designed to investigate the effect of estrogen antagonist on survival rate,gonadosomatic index(GSI),hepatosomatic index(HSI),and expression of the related genes to ovarian development of female Portunus trituberculatus by in vivo experiment,culture experiment and quantitative PCR(q PCR).The results showed that,the different concentration of TAM had no significant effects on the survival rate and HSI among all treatments,but could suppress increase of GSI.The results of q-PCR showed that TAM had significant effects on the expression levels of Vg(vitellogenin),ERR(estrogen related receptor),RXR(retinoid X receptor)and Ec R(ecdysone receptor)genes in different tissues of P.trituberculatus.The expression levels of Vg gene in ovary and hepatopancreas were obviously inhibited by TAM.For ERR gene,low concentration of TAM(6.7 and 13.4?g/g)could promote the ERR transcription in the ovary and thoracic ganglion,while different from the results of low concentration,the significant decrease was found on the ERR m RNA levels in the most examined tissues from the high concentration of TAM treatment(20?g/g)compared to the control treatment.The expression profiles of Ec R affected by TAM was similar with ERR in ovary and hepatopancreas.In addition,the low concentration of TAM could promote the expression of RXR gene in ovary,but no significant differences were found on RXR expression levels in the hepatopancreas.In conclusion,these results suggested that TAM could modulate inhibition the Vg expression levels,possible resulting in the low GSI of female P.trituberculatus,ERR,RXR and Ec R may be involved in regulatory processes of estrogen or exogenous estrogen antagonist on ovarian development,and the underlying mechanism and signaling pathway remains unclear and need more further investigations in the future. |
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