以基因組螢光原位雜交探討蝴蝶蘭雜交種之基因組組成

Abstract

八種蝴蝶蘭雜交種進行基因組螢光原位雜交的結果，四種雜交種Phalaenopsis mannii x P. stuartiana、P. violacea x P. equestris、P. stuartiana x P. amboinensis、P. equestris x Doritis pulcherrima，不使用覆蓋DNA即可清楚區分兩親本的染色體，顯示大小染色體所含重複性DNA的種類及數量不同，且小染色體中節處含特有的重複性序列，因此具大染色體的蝴蝶蘭與具小染色體的蝴蝶蘭同源性較低，親緣關係較疏遠。雜交種P. mannii x P. lueddemanniana使用50倍覆蓋DNA時才能區分兩親本染色體，兩者同源性較高，親緣關係較接近。雜交種P. sanderiana x P. aphrodite及P. mannii x P. violacea，在加或不加覆蓋DNA的情況下，均無法區分兩親本的染色體，顯示P. sanderiana與P. aphrodite間以及P. mannii與P. violacea間其重複性DNA序列有極高之同源性。雜交種P. violacea x D．pulcherrima不使用覆蓋DNA即可辨別兩親本染色體，添加50倍覆蓋DNA，更可清楚區分，顯示此兩種蝴蝶蘭之重複性DNA序列稍有差異。

Genomic in situ hybridization was used to investigate the genome organization and their relationships of eight Phalaenopsis hybrids. The result revealed that (1) In hybrids P. mannii x P. stuartiana, P. violacea x P. equestris, P. amboinensis x P. stuartiana, P. equestris x D. pulcherrima, the parental genomes could be distinguished without blocking DNA as result of differences in kind and amount of repetitive sequences. Species with small chromosomes had their own specific sequences at the centromeric regions. Thus it is considered that these species were remotely related. (2) Except 50-fold blocking DNA the parental chromosomes of hybrid P. mannii x P. lueddemanniana could not be identify. It is suggested that these two species were closely related. (3) In hybrids P. mannii x P. violacea, P. aphrodite x P. sanderiana, the parental chromosomes could not be discriminated even with 100-fold blocking DNA. It is indicated that species with small genomes or with large genomes contained high homology of repetitive sequences respectively. (4) In hybrid P. violacea x D. pulcherrima, the two genomes could be differentiated with or without blocking DNA. The relationships between these two species seemed distinctly.