牙鲆gnrh基因的表达分析

本文通过qPCR方法，研究了我国重要海水鱼类——牙鲆（Paralichthys olivaceus）雌、雄成体组织以及性腺分化期的脑、性腺中gnrh1、gnrh2和gnrh3的表达水平。结果显示，gnrh1分布于所有检测的组织：在脑、垂体、肾脏和肝脏中高表达，在性腺中表达相对较低；gnrh2则在雌、雄性的肝脏以及雄性的肠、肾脏、眼睛和头肾中；而gnrh3只在雄性的肾脏、眼睛和肌肉中检测到微弱表达。人工诱导的牙鲆雌核发育鱼苗分别用17β-雌二醇（E₂）和17α-甲基睾酮（MT）处理，使其分化为雌性或雄性个体表型。在性腺分化期的脑中，gnrh1的表达呈现上升趋势，在全长（total length，TL）4 cm鱼苗中，E₂组的表达显著高于MT组（P<0.05）；gnrh2在2 cm TL时E₂组显著高于MT组（P<0.05），随后在E₂和对照组的表达水平均出现下降趋势；gnrh3在2 cm TL时E₂和对照组的表达均显著高于MT组（P<0.05），自6 cm TL时MT和E₂组的表达开始下降。在性腺中，三种gnrh在性腺分化前2 cm TL表达量都相对较高，随后呈现下降趋势。综上，推测牙鲆gnrh1可能参与了性腺分化的启动、分化过程及性腺发育，gnrh2主要参与了性腺分化的启动，gnrh3主要参与了性腺分化的启动和分化过程。

Expression analysis of gnrh in Paralichthys olivaceus

Differential expression levels of gonadotropin-releasing hormone (gnrh) 1, gnrh2, and gnrh3 in male and female adult tissues, as well as the brain and gonad during gonadal differentiation period of the olive flounder Paralichthys olivaceus, an important marine cultural fish in China, were studied using a quantitative polymerase chain reaction. Results showed that gnrh1 was distributed in all detected tissues of adult male and female fish, and highly expressed in the brain, pituitary gland, kidney, and liver, but relatively weakly in the gonads. Gnrh2 was detected in the liver of both male and female fish, as well as the intestine, kidney, eye, and head kidney of the male. Gnrh3 was weakly expressed in the kidney, eye, and muscle of the male fish. Using 17-beta estradiol (E2) and 17-alpha methyl testosterone (MT), the flounder gynogenetic juveniles were induced to differentiate into male and female individual phenotype, respectively. In the brain during the gonadal differentiation period, gnrh1 showed an upward trend expression at 2-8 cm total length (TL), and at 4 cm TL, with significantly higher expression levels in the E2 group than those in the MT group (P<0.05). Gnrh2 expression levels at 2 cm TL in the E2 group were significantly higher than those in the MT group (P<0.05) and were downregulated from 3 cm TL in the E2 and control groups. No significant difference was found in the MT group at different TL points. Gnrh3 expression levels at 2 cm TL in the E2 and control groups were both significantly higher than those in the MT group (P<0.05) and were downregulated from 6 cm TL. In the gonad during the flounder gonadal differentiation period, gnrh1, gnrh2, and gnrh3 were all expressed relatively high at 2 cm TL, and then were downregulated from 3 cm TL. In summary, gnrh1, gnrh2, and gnrh3 might play roles in the initiation of the flounder gonadal differentiation, gnrh1 and gnrh3 participate in the gonadal differentiation, and gnrh1 is also involved in the gonadal development. The study will help elucidate the roles of gnrh in fish gonadal differentiation and development.