极小种群植物距瓣尾囊草的核型及5S rDNA-FISH分析

Karyotype and 5S rDNA-FISH Analysis of an Extremely Small Population Urophysa rockii Ulbr.

采用改良的去壁低渗火焰干燥法制片,对距瓣尾囊草(Urophysa rockii Ulbr.)的染色体数目和核型进行分析;并以5S rDNA为探针,利用荧光原位杂交技术对5S rDNA位点进行定位。结果表明,距瓣尾囊草的染色体总数为14条,染色体基数为7,倍性为二倍体;该植物的染色体相对长度组成为2n=14=2L+2M2+10M1;染色体核型公式为2n=2x=14m,无随体,着丝粒平均指数为44.09,核型不对称系数为55.91,染色体核型属于'1A'型,在系统进化上处于比较原始的状态;同时,具有2个5S rDNA位点,且位于一对同源染色体(1号染色体)长臂的近着丝粒位置,由此可见5S rDNA可以作为该植物染色体识别的有效标记。综上所述,本研究解析了该植物的系统学和细胞学特征。

In this study the modified wall degradation hypotonic method was used for unlocking the chromosome number and the karyotype of Urophysa rockii Ulbr.,a plant species of which is distributed in an extremely restricted area.The 5 S rDNA sites on chromosomes were also analyzed of Urophysa rockii Ulbr.via fluorescence in situ hybridization(FISH).The results indicated that Urophysa rockii Ulbr.is a diploid species with 14 chromosomes(n=7).The relative length of chromosomes was 2 n=14=2 L+2 M2+10 M1,and no satellite chromosome was detected with the karyotype formula.The average centromere index and karyotype asymmetry coefficient were 44.09 and 55.91,respectively.The karyotype belonged to 1 A type,suggesting that phylogenetic evolution is relatively primitive.Furthermore,two 5 S rDNA sites were detected close to the centromere of the long arm of chromosome 1.Taken together,these results may provide shed-light on systematology and cytology of Urophysa rockii Ulbr.