温度对许氏平鲉性腺分化的影响及其机制

Effects of temperature on gonadal differentiation of black rockfish (Sebastes schlegelii) and its mechanism

本研究以许氏平鲉为实验对象,设置3组不同温度,即高温组(24℃)、对照组(20℃)和低温组(16℃),利用组织切片技术、酶联免疫法(ELISA)和实时荧光定量PCR(q RT-PCR)等技术探究温度对许氏平鲉性腺分化的影响及其潜在机制。结果显示,在40 dpb时,24℃下性腺发育最快,16℃下最慢,24℃、20℃和16℃下雌性率分别为70.0%、42.9%和33.3%。24℃和20℃下,E2在较高水平持续时间较长,T水平在30~35 dpb时急剧降低,16℃下的E2水平迅速下降,35 dpb时T仍处于较高水平,说明在性腺分化期间,温度较高时,E2水平较高,T水平较低,性腺偏雌性发育;反之,性腺偏雄性发育。在24℃下,35~40 dpb时的cyp19a1a mRNA的表达显著上调,可能与高温导致性腺分化偏雌性发育有关;在16℃下,30~50 dpb时ERβ2 mRNA的表达显著下调,说明ERβ2的表达被抑制可能与性腺偏雄性发育有关;24℃和20℃下,foxl2 mRNA的表达在25~35 dpb时处于较高水平,而低温组在30 dpb时表达水平开始上升,说明foxl2在性腺分化早期的高表达水平可能与卵巢分化的速率有关;在30~50 dpb,sox3、sox9和dmrt1的表达水平变化总趋势基本一致,说明三者之间的表达有一定的联系,可能与精巢的分化速率有关。

In this study, the black rockfish (Sebastes schlegelii) was selected as the research object. Three groups with different temperature treatments were set up, including high temperature group (24 ℃), control group (20 ℃) and low temperature group (16 ℃). Histology, ELISA and qRT-PCR methods were used to investigate the effect of different temperatures on gonadal differentiation and the potential mechanism. The results showed that at 40 dpb, the gonads developed fastest at 24 ℃, and slowest at 16 ℃. The female ratio were 70.0%, 42.9% and 33.3%, at 24 ℃, 20 ℃ and 16 ℃ respectively. At 24 ℃ and 20 ℃, high level of E2 lasted for a long time and T level decreased sharply at 30-35 dpb. At 16 ℃, E2 level dropped rapidly, and the T was still at a high level at 35 dpb. It indicated that at high temperature, the E2 level was high, whereas T level was fairly low during gonad differentiation, and the gonad tended to be female;on the contrary, the gonad preferred to be male. At 24 ℃, the cyp19a1a mRNA expression was significantly up-regulated at 35-40 dpb, which may be associated with the partial female gonad development at high temperature. At 16 ℃, The ERβ2 mRNA expression was significantly decreased at 30-50 dpb. The inhibition of ERβ2 expression may be related to the partial male gonad development at low temperature. At 24 ℃ and 20 ℃, foxl2 mRNA expression was at relative high level at 25-35 dpb, and the expression level of low temperature treatment group began to increase at 30 dpb. It indicated that the high expression of foxl2 may be related to the rate of ovarian differentiation during the early stage of gonadal differentiation. At 30-50 dpb, the general trend of expression levels of sox3, sox9 and dmrt1 was consistent, indicating there is a connection between the expressions of the three genes, which might be related to the rate of testis differentiation.