摘要
本研究克隆获得银鲳（Pampus argenteus）雌激素受体α（estrogen receptorα,ERα）基因的部分c DNA序列,长度196 bp,编码65个氨基酸。经BLAST比对,与其它鱼类ERα基因序列的一致性在89%~93%之间,证明实验所得序列为银鲳ERα基因的部分片段。以1年龄雌性银鲳为实验对象,配制了4组等氮、等能及等脂的实验饲料,分别以100%鱼油（FO组）、70%鱼油和30%大豆油（FSO组）、30%鱼油和70%大豆油（SFO组）、100%大豆油（SO组）为脂肪源,研究银鲳在卵黄发生期间组织中ERα基因表达量的变化以及饲料n-3LC-PUFA对其组织表达的影响,实验周期185 d。结果表明,在卵黄发生中期与后期,肝脏与卵巢中ERα基因表达量均显著高于卵黄发生前期（P〈0.05）;卵黄发生后期肝脏组织中ERα基因表达量虽较卵黄发生中期呈升高趋势,但除了SO组之外,两者之间无显著性差异（P〉0.05）;而卵巢组织中ERα基因表达量在整个卵黄发生期间均呈现显著升高趋势（P〈0.05）。饲料n-3LC-PUFA对肝脏与卵巢ERα基因表达量的影响在卵黄发生前期均未表现出明显的组间差异,但在卵黄发生中期与后期,饲料中较高的n-3LC-PUFA含量显著提高了组织中ERα基因表达量。在卵黄发生中期与后期,FO与FSO组肝脏与卵巢组织中ERα基因表达量均分别显著高于SO组（P〈0.05）。双因素方差分析结果表明,饲料n-3LC-PUFA与卵黄发生时期对银鲳组织中ERα基因表达量均具有显著性影响,且两者对组织中ERα基因表达量存在显著性的交互作用。
It has been reported that n-3 long-chain polyunsaturated fatty acids（ n-3 LC-PUFAs） such as eicosapentaenoic acid（ EPA,20： 5n-3） and docosahexaenoic acid（ DHA,22∶ 6n-3） play critical roles in cell permeability and enzyme activity. Marine teleosts can not synthesize LC-PUFAs from 18-carbon precursors due to a deficiency in Δ5-desaturase. Therefore,it is imperative that teleost diets contain LC-PUFAs. The importance of LC-PUFAs, especially n-3 LC-PUFAs, in fish broodstock nutrition has been extensively studied. Dietary n-3 LC-PUFAs affect spawning performance,egg and larval quality,and egg fatty acid composition of broodstock. In humans,fatty acids,especially PUFAs,are cell signaling molecules,structural compounds and energy sources. PUFAs are crucial for mediating immunological,metabolic,and endocrine signals within the uterine-fetal-placental unit. PUFAs are precursors of cell signaling molecules（ e. g.,eicosanoids）,and there is evidence that they regulate membrane signal transduction pathways and steroid hormone action,by modulating the binding of estrogen,progesterone,and glucocorticoids to their intracellular receptors. Therefore,PUFAs act as endogenous modulators of key enzymes involved in steroid metabolism.While most studies have focused on the effects of diet on body composition,growth performance,egg quality and larval survival rate,few studies have investigated the effects of nutrients on hormone synthesis during gonadogenesis. Pituitary gonadotropin hormone（ Gt H）,follicle-stimulating hormone（ FSH）,and luteinizing hormone（ LH） are involved in gametogenesis and sexual maturation in teleosts. In response to Gt H,cholesterol is converted into testosterone（ T） and 17β-estradiol（ E2）. Sex steroid hormones play important roles in vertebrate reproduction. In several teleost species,E2 and T,which are produced in gonadal tissues under the control of Gt H,are essential in gametogenesis. Estrogen receptors（ ER） are members of steroid receptor family of ligand-activated nuclear receptors and interact as homo- or heterodimers on estrogen responsive elements of target gene promoters to enhance or repress transcription. A key step in the maturation process is the production of E2 by the developing ovarian follicle. E2 is transported in the bloodstream to the liver where it binds to ER in the hepatocyte cytoplasm. The E2– ER complex in turn acts as a promoter for the expression of the gene or genes coding for Vtg,which is then sequestered into the developing oocyte through a process of receptor-mediated endocytosis. Pampus argenteus is a novel aquaculture species in China. In spite of important technical development and intense research in silver pomfret,some bottlenecks still limit the expansion of its industry. One is the lack of a suitable formulated diet for broodstock,which leads to the poor quality of gonads in cultured broodstock. The effects of diet on the body composition and growth performance of juvenile silver pomfret have been extensively studied. However,there is little evidence on the effects of diet on the reproductive system. The objective of this study is to investigate the molecular cloning of ERα from silver pomfret,and the response of its expression to dietary n-3 LC-PUFA levels during vitellogenesis. In the present study,the partial c DNA of ERα was cloned from silver pomfret Pampus argenteus,which was 196 bp,encoding 65 amino acids. The results of BLAST showed that the sequence was89- 93% similar to those of other fish species,implying that the obtained sequence was the ERα of silver pomfret. For the purpose of studying the changes of tissue ERα gene expression during vitellogenesis and the response of its expression to dietary n-3 LC-PUFA levels,four iso-nitrogenous,iso-energetic,and iso-lipidic（ 16% lipids） experimental diets were formulated： 100% fish oil（ FO）,70% fish oil and 30% soybean oil（ FSO）,30% fish oil and 70% soybean oil（ SFO）,and 100% soybean oil. Female silver pomfret（ 1 y of age） were assigned to one of the four diets（ with three replicates each） for 185 days. The results showed that hepatic and ovarian ERα gene expression in vitellogenesis and post-vitellogenesis stages were significantly higher than those in pre-vitellogenesis（ P 0. 05）. Hepatic ERα gene expression levels in the postvitellogenesis stage were higher than those in vitellogenesis stage,but not significantly（ except SO group）.However,the ovarian ERα gene expression levels changed constantly and significantly during vitellogenesis（ P 0. 05）. In pre-vitellogenesis,there was no significant difference in hepatic and ovarian ERα gene expression levels among groups. However,in vitellogenesis and post-vitellogenesis stages,FO and FSO had higher ERα gene expression levels than SO（ P 0. 05）. The results of two-way ANOVA indicated that statistically significant effects of both diets and stages were observed for the tissue ERα gene expression,meanwhile significant effects of diet and stage interactions were also recorded.
出处
《海洋渔业》
CSCD
北大核心
2016年第2期157-165,共9页
Marine Fisheries
基金
国家自然基金项目(31202009)
上海市科技兴农重点攻关项目(沪农科攻字2013-2-1)
中央级公益性科研院所基本科研业务费(东2014Z02-2)
作者简介
彭士明，男，博士，副研究员。E—mail：shimingpeng@163．com
