益母草基于45S rDNA染色体定位的核型分析及减数分裂观察

Karyotype Analysis Based on Physical Mapping of the 45S rDNA and Meiotic Observations in Leonurus japonicus Houtt

以番茄的45SrDNA为探针,采用荧光原位杂交(fluorescence in situ hybridization,FISH)技术与核型分析相结合的方法,对益母草(Leonurus japonicus Houtt)的核型和45S rDNA在染色体上的定位进行了研究,同时采用压片法观察了其花粉母细胞减数分裂中染色体的行为。结果表明,益母草绝大多数花粉母细胞减数分裂中染色体的行为正常,终变期形成10个二价体,佐证了益母草的染色体数目为2n=20,且为二倍体,其减数分裂为同时型,花粉粒育性为97.10%。益母草体细胞有丝分裂中期染色体上具有2对45S rDNA杂交信号,分别位于第2号染色体短臂的末端和第3号染色体短臂近着丝粒处,益母草的核型公式为2n=2x=20=2m+16sm(2SAT)+2st,染色体相对长度组成为2n=2L+8M2+10M1,最长染色体与最短染色体的比值为1.58,核型不对称系数为69.39,染色体相对长度变异范围为8.05%～12.73%,其核型为"3A"型。基于上述结果绘制了益母草的核型模式图。

Karyotype analysis was performed for Leonurus japonicus Houtt with the localization of 45S rDNA loci by using the rDNA from Lycopersicon esculentum as probe.The meiotic observations showed that the chromosomes were paired as 10 bivalents in its pollen mother cells at diakinesis,indicating that the plant has 2n = 20.The meiotic divisions belong to the simultaneous type and the stainability of the pollen grains was 97.10%.The signals from 45S rDNA probe were detected at the terminal parts of the short arms of second pair of chromosomes and central parts of the third pair of chromosomes.The karyotype formula was 2n = 2x = 20 = 2m ＋ 16sm（2SAT）＋ 2st,with the constitution of relative length being 2n = 2L ＋ 8M2 ＋ 10M1.The ratio of the longest /the shortest chromosomes（L/S）was 1.58,and the asymmetry index was 69.39.The chromosome relative length ranged from 8.05% to 12.73%,and karyotype type belonging to＂3A＂.The idiogram was established for the species.