中华鲟(Acipenser sinensis)间的长度变异与个体内的长度异质性

Mitochondrial DNA Length Variation and Heteroplasmy in Chinese Sturgeon (Acipenser sinensis)

用PCR技术扩增中华鲟（Acipensersinensis）线粒体DNA（mtDNA）控制区（D－loop）时，发现中华鲟天然群体内存在个体间和个体内的mtDNA长度变异现象。DNA测序表明，长度变异发生在mtDNAryloop靠近tRANpro的位置，由长约82碱基对（bp）的重复序列串联形成的。由个体内mtDNA长度变异造成的异质性个体比例为57.4％，非异质性（同质性）个体的比例为426％。非异质性个体间的mtDNA的大小也不一样，存在长度变异。在非异质性个体中，有2、3、4、5个串联重复序列形成的4种分子类型的情况，其重复序列出现的频率从高到低的循序是3→2→4→5。在异质性个体中，同一个体由2种不同分子组合的异质体最普通，占77.78％3种不同分子组合的频率次之，占18.520。4种不同分子组合的异质体比例最少，占3．70％。没有发现由5种不同分子组合的异质体。对所有异质体混合分析表明，各种类型的重复序列出现的比例与非异质体的类似，即分子大小（含重复序列数）从高到低的顺序为3→2→4→5→1。对47尾中华鲟的个体内和个体间的遗传多样性指数分析发现，有65．3％遗传变异表现在群体内的个体间，有347％的遗传变异表现在个体内。由mtDNA长度异质性造成的个体内的多样性是中华鳍物种遗传多样性的另一途径。

The D-loop of mitochondrial DNA from Chinese sturgeon (Acipenser siniensis)was amplified using PCK The length variations among individuals and withinindividual (heteroplasmy) were detected. DNA sequence analysis revealed thatinterindivadual and intraindividual length variation occurred within D-loop near tRNA,and caused by tandam repeat with 82bp in length. Out of 47 individuals, 27(57.4%)individuals were heteropasmy whereas 20 individual (42.6%) were homoplasmic. Thelength variation was also found among homopasmic individuals. In homoplasmicindividua four different size classes (number of tandem repeats) eg. 2,3,4 or 5 repeatswere noted. The frequencies of size classes from the highest to the lowest were 3→2→4 →5. In heteroplasmy tWo molecular size classes coexisted in an individual wasmost common (77.78%). The second type of heteroplasmy was three size classescoexisted (18.52%) and the lowest one was four size classes together in an individual(3.70%). No five different size classes coexisted in an individual was found. Throughdensitometry of DNA bands the frequencies of mtDNA size classes were determinedfor the sample of individuals, and the frequency distribution of repeats from thehighest to the lowest was similar to that in homoplasmy (3→2→4→5→1). Thediversity within each heteroplasmic individual was carried out and genetic diversity athierarchical level was analyzed. 65. 3% of genehc diversihes were from amongindividuals in population and 34.7% of genehc diversities were from within individual.The mtDNA length variation within individual (heteroplasmy) is another geneticdiversity resource for Chinese sturgeon.