核糖体DNA在厦门白姑鱼和大黄鱼染色体上的比较定位

为了探究石首鱼核型微观结构上的变化,实验利用荧光原位杂交(fluorescence in situ hybridization,FISH)比较定位了厦门白姑鱼和大黄鱼18S rDNA和5S rDNA的分布特征。结果表明,厦门白姑鱼与大黄鱼在宏观核型以及18S rDNA和5S rDNA染色体分布等3个方面均存在较大差异。厦门白姑鱼的核型公式为2n=48t,臂数FN=48;单对18S rDNA信号分布于1号染色体臂间;单对5S rDNA信号分布于3号染色体近着丝粒区域。大黄鱼的核型公式为2n=2sm+4st+42t,臂数FN=50;单对18S rDNA信号分布于18号染色体短臂端部;5S rDNA信号9~11对,除一对分布于臂间外,其余全部分布于着丝粒端或短臂端部。综合其他石首鱼核型数据可以推断:厦门白姑鱼呈现原始核型特征,而大黄鱼核型是原始核型经染色体重排和/或转座衍生的特化核型;石首鱼宏观核型和18S rDNA分布模式总体保守,仅少数物种存在变化,而5S rDNA位点的分布模式存在高度的种间变化。本研究首次揭示了石首鱼物种间核型微观结构的变化,为进一步开展石首鱼分子细胞遗传学研究奠定了基础。

Comparison of chromosome mapping of rDNA between Argyrosomus amoyensis and Larimichthys crocea

Ribosomal DNAs were mapped comparatively with fluorescence in situ hybridization (FISH) in Argyrosomus amoyensis and Larimichthys crocea to explore the variations of karyotype microstructure among Sciaenids. The results showed that the karyotypes were quite different between A. amoyensis and L. crocea referring to macrokaryotype, and distribution mode of 18S rDNAs and 5S rDNAs. In A. amoyensis, the karyotype is 2n=48t (FN=48); single pair of 18S rDNA signals were mapped at interstitial region of Chromosome 1; and single pair of 5S rDNA signals were located at proximal region of Chromosome 3. In L. crocea, the karyotype is 2n=2sm+4st+42t (FN=50); single pair of 18S rDNA signals were mapped at terminal region of short arm of Chromosome 18; and 9~11 pairs of 5S rDNA signals distributed mostly on centromeric termini of acrocentric chromosomes or terminal on the short arms. Together with the available cytogenetic data of Sciaenids, the following conclusions were drawn:(1) the karyotype of A. amoyensis represents characteristics of ancestral karyotype in Sciaenidae, while the karyoytpe of L. crocea was derived from the ancestral karyotype through rearrangement and transposition; (2) the macrokaryotype and the location of 18S rDNA sites were rather conservative in Sciaenidae with several exceptions, while the 5S rDNA sites varied dynamically among species. Hence, further studies to investigate microstructure variations of karyotypes among Sciaenid species with FISH should be encouraged.