草鱼线粒体型超氧化物歧化酶的生化遗传特性

超氧化物歧化酶 (SOD)是一种对生物细胞保护至关重要、在进化上比较保守的酶。因此 ,超氧化物歧化酶作为分子钟或分子标记已被广泛应用于生物进化研究、群体遗传结构分析以及品系鉴定。但鱼类SOD的生物化学和遗传学特性都尚未进行过系统和深入的研究。为使这一重要的分子标记能更好地应用于鱼类遗传育种、种质资源保护以及进化研究 ,本实验采用聚丙烯酰胺梯度凝胶垂直电泳法 ,研究了草鱼线粒体型超氧化物歧化酶 (fm SOD)的同功酶形式 ,生化遗传表型、亚基组成以及金属类型。实验结果表明 ,草鱼fm SOD有三种不同的同功酶形式 ;按从正极到负极的排列分别命名为fm SOD 1 ,fm SOD 2 ,fm SOD 3。这三种不同的fm SOD在草鱼群体中可构成 3种不同的生化遗传学表型 :表型 1个体只含有迁移率最快的fm SOD 1同功酶 ;表型3个体只含有迁移率最慢的fm SOD 3同功酶 ;而表型 2个体中含有所有三种不同形式的同功酶。在野生草鱼群体中 ,存在所有三种表现型 ;而在基因纯合型的雌核发育草鱼群体中只检测到表型 1和表型 3。野生草鱼群体中三种表现型的个体数之比符合一对等位基因分离的 1∶2∶1孟德尔遗传分离比例。由这些实验结果得出以下结论 :(1 )草鱼fm SOD是由细胞核DNA上的基因所编码而不是由线粒体DNA上的基因所编码的

Genetic and biochemical characteristics of mitochondrial superoxide dismutase in grass carp Ctenopharyngodon idellus

Superoxide dismutase is an evolutionarily conserved enzyme with an important role in protecting organisms and cells from the damages caused by oxygen free radicals. As a molecular clock and genetic marker, superoxide dismutase has been widely used in evolutionary studies, population genetics, and identification of different strains in the same species. However, the biochemical and genetic features of the mitochondrial superoxide dismutase have not been well characterized in fishes. In this study, we investigated the genetic phenotypes and biochemical features of grass carp Ctenopharyngodon idellus mitochondrial superoxide dismutase (fm-SOD) with polyacrylamide gradient gel electrophoresis. Our data revealed three isoforms of fm-SOD which were named fm-SOD 1, fm-SOD 2 and fm-SOD 3 according to their positions from the positive pole to the negative pole. The combination of three isoforms of fm-SOD constitute three distinct biochemical phenotypes. Phenotype 1 was only associated with the fastest migratory isoform fm-SOD 1 and phenotype 3 with the slowest migratory isoform fm-SOD 3, while phenotype 2 was associated with all three isoforms. In the wild group of grass carp, all three phenotypes were observed, whereas in the mito-gynogenetic group, only phenotypes 1and 3 were observed. The ratio of the three phenotypes in the wild group was consistent with the 1: 2: 1 ratio ofMendelian inheritance for 2 alleles of a single locus in the autosomal chromosomes. These results suggested that: (1) the mitochondrial superoxide dismutase gene in grass carp resided in chromosomes instead of mitochondrial DNA; (2) mitochondrial superoxide dismutase was encoded by a single locus; (3) there were at least two variant alleles in grass carp and (4) the fm-SOD is composed of two subunits. In addition, the fm-SOD was sensitive to the mixture of 15% ethanol and 25 % chloroform but resistant to H2O2, indicating that the fm-SOD in grass carp is Mn-SOD Acta Zoologica Sinica 50(3): 389-394, 2004].