银鲫两个雌核发育克隆间两性生殖子代的遗传多样性分析

STUDIES ON GENETIC DIVERSITY IN GONOCHORISTIC OFFSPRING PRODUCED FROM MATING BETWEEN TWO DIFFERENT GYNOGENETIC CLONES OF SILVER CRUCIAN CARP

本研究在揭示银鲫两性生殖方式的基础上,对尾人工雌核发育克隆F的卵子与一尾天然雌核发育克隆D的精子授精所获得的18尾FD后代及其亲本进行RAPD分析。扩增结果表明,在18尾FD子代中可检测到丰富的DNA多态片段,这些多态片段来自于银鲫两性生殖的重组。FD子代的扩增图谱不仅与母本的扩增图谱不同,而且个体间的扩增图谱也存在着较大的差异。这些差异的DNA片段根据其来源可基本分为四类。与异精刺激雌核发育的子代的情况不同,两性生殖FD子代间平均遗传距离高达0.23±0.123,远远高于异精刺激雌核发育的子代间的平均遗传距离(约<0.01)。在FD的三类表型中,SD个体间的平均遗传距离最大,为0.235±0.097;其次是SF间的平均遗传距离,为0.148±0.073;而NL间的平均遗传距离最小,为0.094±0.083。银鲫的遗传多样性和两性生殖方式为银鲫种群提供了丰富的遗传变异,创造了更多的遗传多样性。在分析了2320条(平均每个个体116条)可分辨的扩增带的基础上,采用NJTREE构建了呈现FD个体间及其与亲本相似性的分支图。NL3与母本的相似度最高,SD3与父本的相似度最高。在FD三种类型中,SD与NL和SF的平均遗传距离较大(>0.31),而NL和SF的平均遗传距离仅为0.124。母本与父本的遗传距离约为0.35,与以前的研究结果类似,而FD18尾个体与父母本的平均遗传距离均约为0.32,基本一致。但将18尾个体按体型分别统计平均遗传距离,不同的体型与父母本的相似性存在着较大差别。母本与SF的相似率最高,约为71%;父本与SD的相似率最高,约为70%。这可能由于扩增出一些与表型相关的DNA片段,从而导致了FD三种类型与亲本的相似性与表型相关。银鲫具有两种生殖方式的揭示将为解决长期困惑进化遗传学家的难题寻找到一个新的突破口,也进一步确立了银鲫在单性脊椎动物和多倍体脊椎动物进化遗传学研究中的特殊意义。

Based on the discovery of gonochoristic reproductive mode in silver crucian carp ( Carassius auratus gibeiio) , 18 individuals from the mated offspring between clone F and clone D and their parents were analyzed using 11 RAPD primers. The mated offspring differentiated into three phenotypes. One phenotype is similar to that of clone F (SF) . The second is similar to that of clone D (SD). The third shows a novel longer and thinner body type (NL). Electrophore-togram results show abundant polymorphic DNA fragments among individuals in the FD mated offspring. Obviously, the polymorphic DNA fragments originate from the genome recombination owing to the gonochoristic reproductive mode. The FD mated offspring amplify different fingerprints from maternal , and their fingerprints are different from each other. These different DNA fragments can be divided into four groups according to their origin. The average genetic distance among individuals from the FD offspring (0.23 ±0. 123) is much higher than that of allogynogenetic offspring, which is only about 0. 01. Of the three phenotypes in the FD offspring, the average distances among SD is the highest (0. 235 ± 0. 097). The next is SF phenotype, in which the average distances is 0. 148 ± 0. 073. The average distances among NL is the lowest (0. 094 ± 0. 083). The gonochoristic reproductive mode introduces high genotypic variability and underlines genetic diversity. A dendrogram was constructed by NJTREE cluster analysis based on a total of 2320 distinguishable fragments (116 per individual). NL3 and maternal are most closely related, and SD3 and paternal are most closely related. The average genetic distances between SD and SF or NL ( >0. 31) is higher than that of between SF and NL (0. 124). Consistent with previous study, the genetic distance between maternal and paternal is 0. 35. The average genetic distances between FD offspring and parents are both about 0. 32. But the similarities among the three phenotypes in mated group FD offspring and parents are different. The similarity between SF and maternal (71 % ) is higher than similarities among other phenotypes and maternal. The similarity between SD and paternal (70 %) is higher than similarities among other phenotypes and paternal. The results suggest the similarities among three phenotypes in the FD offspring and parents are related with their phenotypes because some DNA fragments specific for phenotypes were amplified in this study. The revelation about reproductive diversity will be able to open the door in which complicated mechanism has been locked in unisexual organisms for long time, and establish the important roles of silver crucian carp in the studies on evolutionary genetics in unisexual or polyploid vertebrates.