Distribution of ribosomal RNA genes in seven Phalaenopsis species

蝴蝶蘭屬植物依植物外部形態的特徵，將P. equestris, P. celebensis和P. lindenii歸屬於Stauroglottis節；而P. sanderiana, P. stuartiana, P. schilleriana和P. philippinensis則歸屬於Phalaenopsis節。本實驗利用雙標的螢光原位雜交的技術將45S rDNA及5S rDNA定位於此七種蝴蝶蘭的染色體上，其中P. equestris, P. celebensis和P. lindenii均具有兩個45S rDNA及5S rDNA的基因座，與傳統分類將此三種蝴蝶蘭歸屬於同ㄧ個節的結果相吻合；然而屬於Phalaenopsis節的P. sanderiana, P. stuartiana, P. schillerinan和P. philippinensis雖然均具有兩個45S rDNA的基因座，但5S rDNA基因座的數目則有差異，其中P. sanderiana有4個5S rDNA基因座，而其餘三種蝴蝶蘭皆為6個5S rDNA基因座。與前人利用45S rDNA的ITS序列所建立的親緣關係樹，將此四個物種分成兩群的結果相符，因此利用核糖體RNA基因的實質定位可提供蝴蝶蘭屬植物親緣關係的參考。

Based on the morphological characters, Phalaenopsis equestris, P. celebensis and P. lindenii are classified to section Stauroglottis, while P. sanderiana, P. stuartiana, P. schilleriana and P. philippinensis belong to section Phalaenopsis. In this study, the distribution of 45S and 5S ribosomal RNA genes in these seven species was examined using double-target fluorescence in situ hybridization. The results revealed that P. equestris, P. celebensis and P. lindenii all possess two 45S rDNA and 5S rDNA loci, consistent with the traditional taxonomic status. Although two 45S rDNA loci were found in P. sanderiana, P. stuartiana, P. schilleriana and P. philippinensis, the number and location of 5S rDNA sites varied. P. sanderiana had four 5S rDNA loci, whereas P. stuartiana, P. schilleriana and P. philippinensis contained six 5S rDNA loci. It is correlated well with a previously constructed phylogenetic tree using internal transcribed spacer (ITS) region of 45S rDNA. The distribution of ribosomal RNA genes provided more information concerning Phalaenopsis species phylogenetic relationships.