3种淡水鱼GSTR的cDNA克隆与肝脏组成型表达比较

Cloning and liver constitutive expression of GSTR in three freshwater fishes

比较不同生态习性淡水鱼类微囊藻毒素去毒能力与其肝脏II相去毒酶Alpha-及Rho-谷胱甘肽S-转移酶(glutathione S-transferase,GST)基因组成型表达之间的关系.采用RT-PCR及RACE方法成功克隆鲢鱼(Hy-pophthalmichthys molitrix)、尼罗罗非鱼(Oreochromis nilotica)、草鱼(Ctenopharyngodon idellu)肝脏Rho-GST(GSTR)基因cDNA全序列.应用半定量PCR方法以β-肌动蛋白为外参照,研究鲢鱼、尼罗罗非鱼、草鱼肝脏Alpha-GST(GSTA)及GSTR基因的组成型表达水平.结果表明,3种淡水鱼类微囊藻毒素去毒基因GSTR序列全长分别为1 078 bp、904 bp、1 104 bp.鲈形目鱼类的罗非鱼GSTR基因组成型表达相对较高,而鲤形目鱼类的鲢鱼、草鱼GSTA基因组成型表达相对较高.可见不同生态习性淡水鱼类GST基因组成型表达的高低可能与3种淡水鱼类生态习性及去毒能力有关,但对于不同生态习性淡水鱼类去毒能力的分子机制尚待进一步研究.

To compare the constitutive expression level of the liver Rho-and Alpha-class glutathione S- transferases （GST） gene which are the main types to detoxify mieroeystin in three freshwater fishes. The full-length eDNAs encoding rho-elass GST were cloned and sequenced from the hepatopanereas of silver carp （Hypophthalmichthys molitrix）, Nile tilapia （Oreoehromis nilotiea） and grass carp （Ctenopharyngodon idellus） by RT-PCR and RACE method. Using beta-actin as external control, liver Rho-elass and alphaclass GST gene expression levels among these freshwater fishes were also studied. The full-length eDNAs encoding Rho-class GST are 1 078 bp, 904 bp, 1 104 bp, respectively. Liver mRNA constitutive expression levels of GSTR gene were higher than those of GSTA gene in Nile tilapia. However, GSTA mRNA expression levels were higher than GSTR gene in silver carp and grass carp. The difference of detoxifieation ability to MC-LR in different freshwater fishes is relative to phase II detoxified enzyme GST and the molecular mechanism for microcystin detoxification abilities of the freshwater fishes were discussed.