黄斑蓝子鱼CRH基因的克隆及其在浅水应激后的mRNA表达

鱼类应激时主要启动两种生理反应系统,即"交感-嗜铬组织"系统/和/或"下丘脑-垂体-肾间组织轴"(HPI轴)系统.在实际生产操作中,鱼类容易受到浅水暴露应激.为了探讨黄斑蓝子鱼在受到浅水应激后HPI轴是否被激活,本研究克隆了下丘脑中启动HPI轴活性的关键因子—促肾上腺皮质激素释放激素(CRH)的基因,并检测其在应激前和受到浅水应激后不同时间点(0、20、40、60、80 min)的mRNA水平.结果显示,CRH前体的cDNA全长为1025 bp,编码170个氨基酸(aa),分别由一个信号肽(24个aa)、一个功能未知保守区(13个aa)和一个成熟肽(41个aa)组成;该CRH前体和成熟肽与其他鱼类的相应肽分别具有62%-98%和78%-100%的序列相似性.当鱼体受到短暂(4 min)浅水应激后80 min内,脑中CRH mRNA水平在应激前后无显著变化(P>0.05),说明黄斑蓝子鱼在受到急性浅水应激后可能主要启动"交感-嗜铬组织"系统而不是HPI轴.

Cloning of Gene Encoding Corticotrophin-Releasing Hormone （CRH） and Its mRNA Expression after Shallow Water Stress In Siganus Canaliculatus

Two kinds of physiological systems may respond to stress in fish, i.e., the sympathetico-chromaffin system and/or the hypothalamus-pituitary-interrenal （HPI） axis. Fish is easily forced shallow water stress in practical applications. In order to investigate whether the HPI axis is activated after the rabbitfish Siganus canaliculatus was forced shallow water stress, the gene encoding corticotrophin-releasing hormone （CRH）, a key factor triggering the HPI axis in hypothalamus, was cloned and its mRNA level was detected before and at different time points（0, 20, 40, 60, 80min） after shallow water stress. The results showed that the full length of cDNA encoding CRH precursor was 1025 bp, the encoded polypeptide has 170 amino acids （aa） which is composed of a putative signal peptide（24 aa）, a cryptic region （13 aa） and a mature peptide（41 aa）. The rabbitfish CRH precursor and mature peptide shared 62-98% and 78-100% of sequence identity to the corresponding peptides of other fishes, respectively. After the rabbitfish was forced short-time （4 min） shallow water stress, the CRH mRNA level in brain showed no significant difference before and after stress in 80 min （P〉 0.05）. The results suggested that the sympathetico-chromaffin system rather than the HPI axis may be primarily activated when the rabbitfish was forced acute shallow water stress.