鲢鱼、草鱼和尼罗罗非鱼热休克蛋白70基因cDNA全序列的克隆与分析

采用RT-PCR技术和RACE技术分别从淡水食毒藻鱼类鲢鱼（Hypophthalmichthys molitrix）、尼罗罗非鱼（Oreochromis nilotica）及草食性鱼类草鱼（Ctenopharyngodon idella）肝脏扩增出热休克蛋白70（HSP70）cDNA全序列，并与其它鱼类、两栖类和哺乳类动物的HSP70氨基酸进行了同源性比较. 结果表明，鲢鱼、草鱼和尼罗罗非鱼肝脏HSP70基因cDNA全长分别为2356 bp、2348 bp和2242 bp，分别编码649、649和638个氨基酸.鲢鱼、草鱼和尼罗罗非鱼HSP70与其它鱼类、两栖类和哺乳类动物HSP70氨基酸同源性均较高，表明其在进化上高度保守，且承担着重要的生理功能.构建系统进化树发现，鲢鱼、草鱼与其它鲤科鱼类斑马鱼、银鲫（Carassius auratus gibelio）的HSP70氨基酸同源性较高，处于同一进化树分枝；而尼罗罗非鱼HSP70未与其它鲈形目鱼类，如鲷科鱼类聚为一枝，而是占据一个独立的分枝，这与克隆得到的鲢鱼、草鱼肝脏HSP70基因可能为结构型HSP70，而尼罗罗非鱼肝脏HSP70基因可能为诱导型HSP70的结果相一致.

Cloning and analysis of the full-length cDNA sequences of the heat shock protein 70 gene from silver carp,grass carp and Nile tilapia

Heat shock protein 70 (HSP70) full-length cDNAs were cloned from the liver of two phytoplanktivorous freshwater fish, silver carp (Hypophthalmichthys molitrix) and Nile tilapia (Oreochromis nilotica), and one herbivorous fish, grass carp (Ctenopharyngodon idella) using RT-PCR and RACE. Sequence analysis revealed that the silver carp, grass carp, and Nile tilapia HSP70 cDNAs were 2356, 2348, and 2242 bp in length, and contained an open-reading frame (ORF) of 1950 bp (encoding a polypeptide of 649 amino acids), 1950 bp (encoding a polypeptide of 649 amino acids), 1917 bp (encoding a polypeptide of 638 amino acids), respectively. Silver carp, grass carp and Nile tilapia HSP70 sequences are highly homologous to other fish, amphibia and mammals HSP70, which suggests that they play a role in fundamental cellular processes. Results of the phylogenetic analysis revealed that silver carp and grass carp HSP70 formed a cluster with other cyprinid fishes, such as zebrafish and silver prussian carp, but Nile tilapia HSP70 formed a distinct cluster. This is consistent with the result that the cloned silver carp and grass carp HSP70 may belong to heat shock cognate 70, whereas the cloned Nile tilapia HSP70 may be classified as inducible heat shock protein 70.