以5S rDNA基因間空白區序列探討蝴蝶蘭屬植物之親緣關係

Abstract

5S rDNA為聚集型的重複性序列，每一個重複單位包含轉區及基因間空白區，轉錄區為120 bp，具高度保留性，而基因間空白區之序列在物種間的差異則很大，可用於親緣關係較近物種間的分析。本實驗以聚合酵素連鎖反應擴增各種蝴蝶蘭屬植物之基因間空白區序列，做親緣關係樹的分析，依樹型顯示蝴蝶蘭屬植物為單源發生的演化，且可分成7群，其中P. amboinensis、P. venosa和P. violacea屬於同一群，而P. equestris與Phalaenopsis節的P. amabilis、P. aphrodite、P. sanderiana、P. stuartiana、P. schilleriana則屬於另一群，此結果雖然與形態分類不符，卻與蝴蝶蘭雜交種染色體配對情形之研究、RAPD分析及核型觀察的結果一致，至於P. mannii與P. amboinensis及P. lueddemanniana三者間的親緣關係則尚待釐清。

5S rDNA are organized into clusters of tandem repeats with each repeat consisting of a transcribed region of about 120 bp conserved sequences and an intergenic spacer (IGS) region varying in size among species. The divergence of IGS sequences makes it useful for phylogenetic analyses. In this study, IGSs of 28 Phalaenopsis species were amplified by the polymerase chain reaction, cloned, and sequenced. Phylogenetic analysis of IGS sequences revealed that the origin of these species seemed to be monophyletic and could be divided into seven groups. Among them P. amboinensis, P. venosa and P. violacea were grouped together which was consistent with cytogenetic data and RAPD analysis. Similarly, P. equestris, P. amabilis, P. aphrodite, P. sanderiana, P. stuartiana and P. schillerana, were also considered to be closely related species. The relationships among P. mannii, P. amboinensis and P. lueddemannian remains unsolved.