- 學位論文
五種蝴蝶蘭屬植物核糖體 RNA 基因之染色體定位
Chromosome localization of ribosomal RNA genes in five Phalaenopsis species
摘要
五種蝴蝶蘭原生種 P. amabilis 、 P. aphrodite 、 P. bastianii 、 P. pulchra 及 P. tetraspis 皆具 38 條染色體 (2n = 2x = 38) ，但染色體大小有差異。利用螢光原位雜交將兩種 rDNA 定位於染色體上，屬於 Phalaenopsis 節之 P. amabilis 及 P. aphrodite 皆具 1 對 45S rDNA 基因座及 2 對 5S rDNA 基因座，但前者之45S rDNA 基因座具多型性且 2 對 5S rDNA 基因座均位於染色體末端，而後者有1 對 5S rDNA 基因座位於染色體末端，另 1 對 5S rDNA 基因座則位於染色體臂間且具多型性。屬於 Amboinenses 節之 P. bastianii 及 P. pulchra 皆具 1 對 45S rDNA 基因座及 1 對 5S rDNA 基因座，與同節之P. luddemanniana 、 P. fasciata 、 P. mariae 及 P. pallens 相 同，但卻與 P. amboinensis 、 P. venosa 及 P. violacea 分別具 4 ~ 7 對 45S rDNA 基因座及 1 ~ 2 對 5S rDNA 基因座有明顯差異。此外，兩群植物在染色體形態和 DNA 含量亦有很大不同，與利用 5S rDNA 的 IGS 序列以及 45S rDNA 的 ITS 序列所建立之親緣關係樹將此九種蝴蝶蘭分為兩群的結果相符。屬於 Zebrinae 節之 P. tetraspis 具有 1 對 5S rDNA 基因座及 5 對 45S rDNA 基因座，且 45S rDNA 大都位於小染色體上，與含基因組較大的蝴蝶蘭 P. amboinensis、P. venosa、P. violacea 及 P. pulcherrima 有類似的結果，此種特殊分佈是值得探討之問題。
並列摘要
Phalaenopsis amabilis, P. aprodite, P. bastianii, P. pulchra, and P. tetraspis had 38 chromosomes (2n = 2x = 38), but their chromosome size differed. Fluorescence in situ hybridization was used for physical mapping of 5S and 45S rDNAs. P. amabilis and P. aphrodite belonging to the section Phalaenopsis had one pair of 45S rDNA loci and two pairs of 5S rDNA loci. The former had polymorphic 45S rDNA loci and two pairs of the 5S rDNA loci at the terminal site, whereas the latter contained one pair of 5S rDNA loci at the terminal site and the other pair at the interstitial region with polymorphism. Both P. bastianii and P. pulchra of the section Amboinenses possessed one pair of 45S rDNA loci and one pair of 5S rDNA loci. In the same section, P. luddemanniana, P. fasciata, P. mariae and P. pallens not only had the same number of rDNA loci, but also the chromosome size and DNA content were the same as these two species. On the contrary, P. amboinensis, P. venosa and P. violacea had four to seven pairs of 45S rDNA loci and one to two pairs of 5S rDNA loci. In addition, these three species contained larger chromosomes and higher DNA contents. Therefore, these nine species could be divided into two groups. The results were consistent with the phylogenetic tree constructed with IGS region of 5S rDNA and ITS region of 45S rDNA. P. tetraspis classified to the section Zebrinae contained one pair of 5S rDNA loci and five pairs of 45S rDNA loci. The 45S rDNA loci were almost located in the small chromosomes. The similar distribution of 45S rDNA was also observed in the species with larger genomes, such as P. amboinensis, P. venosa, P. violacea, and P. pulcherrima. Further studies are needed to clarify this special phenomenon.