银鲳ghr和igfbp1基因表达特征、组织分布及操作胁迫对其的影响（英文）

Characterization,tissue distribution and growth regulation of ghrs and igfbp1 in silver pomfret(Pampus argenteus) in handling stress

为探讨急性操作胁迫对银鲳生长的影响,首次克隆了3种生长调控相关基因-生长激素受体1(ghr1)、生长激素受体2(ghr2)和胰岛素样受体1(igfbp1),并对3种基因在银鲳肝脏、心脏、性腺、肌肉和肾脏等不同组织中的表达进行了比较。定量表达结果表明3种基因均广泛分布于所研究的各个组织中,而其中肾脏、性腺和心脏中的表达量较其它组织低。在银鲳受到外界操作胁迫刺激后,3种基因呈现不同的表达模式:其中ghr2和igfbp1的表达下调,而ghr2的表达量与对照组无显著性差异。结果表明,ghr2和igfbp1在银鲳生长调节中起到重要的作用;在胁迫环境中,外界刺激可通过下调生长相关基因表达以影响鱼体的生长。

Growth activities are mainly involved by growth hormone/insulin-like growth factors（GH/IGF）axis. GH and IGF are anabolic hormones,which increase muscle mass by stimulating protein synthesis and/or inhibiting protein breakdown. In fish,growth hormone receptor genes（ghrs） encode transmembrane receptor protein for GH. By binding GH,it can activate an intra-and intercellular signal transduction pathway leading to growth. Type 1 insulin-like growth factor-binding protein is encoded by igfbp1 gene,a member of igfbp family. Binding of this protein can prolong the half-life of IGFs and alter their interaction with cell surface receptors. Silver pomfret（Pampus argenteus） is an important commercial fish which has a wide distribution from the Arabian Gulf,the India Ocean and the East China Sea to Southeast Asia. Relevant artificial breeding techniques and P. argenteus reproductive biology have been studied in China and Kuwait since the 1980 s.Due to its sensitivity to many kinds of stress factors,low growth rate and high mortality has been found in P.argenteus during culture practices. However,little is known about its molecular aspects,including gene expression information of growth during stress phase. In the present study,characterization,distribution and expression pattern of growth-related gene（ghrs and igfbp1） responded to acute handling stress are examined.Our aim is to evaluate the effect of acute handling stress on growth in this species. Gene sequence analysis shows that the total length of ghr1,ghr2,and igfbp1 ranges from 1280 to 3625 bp,and encodes amino acids from 64 to 627. Signal peptide sites and transmembrance helices are found in all three genes. GHR1 protein has three functional domains,including GHR binding domain,Erythropoietin receptor（EpoR） domain,and fibronectin type III domain,while GHR2 protein has only two functional domains（GHR binding domain and EpoR domain）. IGFBP-1 protein has an insulin-like growth factor binding protein domain and a Tg I domain. Phylogenetic analysis reveals that P. argenteus is more closely related to the Perciformes. ghr2 and ghr2 genes share higher similarities with Epinephelus coioides. The results of quantitative real-time PCR show that ghrs and igfbp1 are widely expressed in liver,heart,gonad,white muscle and kidney tissues,with relatively lower expression levels in kidney,gonad and heart. When treated with handling stress,different genes have different expression patterns. Expression of ghr2 and igfbp1 is down-regulated,while expression of ghr2 has no significant difference from those in control groups. Results from this study suggests the important role of ghr2 and igfbp1 in growth regulation during stress environment,and acute stress might affect growth activities by down-regulating growth related genes. Results of the present study will be helpful for the furtherstudy of fish growth and effects of environmental stress on it in silver pomfret and other marine fish as well.