Chromosome localization of ribosomal RNA genes in five Phalaenopsis species
Date Issued
2009
Date
2009
Author(s)
Chen, Yi-Syuan
Abstract
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, butlso 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 studiesre needed to clarify this special phenomenon.
Subjects
fluorescence in situ hybridization
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