海岛棉基于双色 FISH 的核型分析

摘要

Through the fluorescence in situ hybridization ( FISH ) of somatic metaphase chromosomes of Gossypium barbadense with the probe of 45S rDNA, six strong NOR (nucleolar organizer region) fluorescent signals were detected, of which 4 were big and 2 were small, and these signals were distributed at the satellite site of corresponding chromosome by combining with DAPI image observation.The FISH of G.barbadense with the probe of genomic DNA ( gDNA) of diploid A-genome asiatic cotton found that:there were hybrid signals in the half of 52 chromosomes;the fluorescent signals were distributed in longer A-subgenomic chromosomes, and directly distinguished the A-subgenomic and D-subgenomic chromosomes of G.barbadense, which directly proved that G.barbadense was originated from two different diploid species .Using the gDNA of A-genome asiatic cotton and 45S rDNA as probes, we conducted dualcolor-FISH ofG .barbadense, and detected not only 6 strong NOR signals but also gDNA hybrid signals in the chromosomes of G.barbadense, and clearly found 2 NOR signals in sub-genome A and other 4 NOR signals in sub-genome D.The karyotype analysis of G.barbadense based on dualcolor-FISH images indicated that:the kary-otypic formula of this cotton species was 2n=4x=52=40m ( 2 SAT)+12sm ( 4 SAT) , belonging to 2A type; there were three pairs of satellite chromosomes, of which one was located in the number 9 of A sub-genome (m type), and the others were located in the number 8 and number 12 of D sub-genome ( sm type) .It was also found that not all A sub-genomic chromosomes of G. barbadense had a bigger relative length than D sub-genomic chromosomes , suggesting that the FISH-based karyotype analysis method was more accurate than traditional methods .%以45S rDNA作探针对海岛棉体细胞中期染色体进行荧光原位杂交（ Fluorescence in situ Hybridization， FISH），检测出6个强的荧光信号（4大2小），结合DAPI图像观察发现信号分布在各自染色体随体位置，称为NOR（Nu-cleolar Organizer Region）信号。以二倍体A基因组棉种亚洲棉基因组DNA（ gDNA）为探针对海岛棉进行FISH，结果发现52条染色体中有无杂交信号的各占一半，荧光信号分布在较长的A亚组染色体上，直接区分开海岛棉A、D亚组染色体，直观证实了海岛棉的异源双二倍体起源。以45S rDNA和A组棉种亚洲棉gDNA作探针对海岛棉进行双色FISH时，结果发现海岛棉染色体上既检测到了6个强的NOR信号又检测出了gDNA杂交信号，且清楚观察到2个NOR信号分布在A亚组上，另4个在 D亚组上。基于该双色FISH图像的核型分析表明，海岛棉的核型公式为：2n＝4x＝52＝40m（2 SAT）＋12sm（4 SAT），属于2A类型，且有3对随体，其中1对定位于A9号染色体，属于中部着丝点（ m）类型；另2对分别定位于D8和D12号染色体上，属于近中部着丝点（ sm）类型；且发现海岛棉A亚组染色体的相对长度的并非全部大于D亚组，两亚组染色体间在长度上存在交叉，说明基于FISH的核型分析比传统方法更为准确。