The evolution of genome size and distinct distribution patterns of rDNA in Phalaenopsis (Orchidaceae)

Abstract Phalaenopsis is a horticulturally important genus of c. 63 spp. native to Southeast Asia. Aiming to understand the genome differentiation and phylogenetic relationships in diploid Phalaenopsis spp., we investigated the nuclear DNA content by flow cytometry karyomorphology and mapped rDNA lo...

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Bibliographic Details
Published in:Botanical journal of the Linnean Society 2017-09, Vol.185 (1), p.65-80
Main Authors: Lee, Yung-I, Chung, Mei-Chu, Kuo, Hao-Chih, Wang, Chun-Neng, Lee, Yi-Ching, Lin, Chien-Yu, Jiang, Hong, Yeh, Chih-Hsin
Format: Article
Language:English
Subjects:
Chromosome rearrangements
Chromosomes
Deoxyribonucleic acid
Differentiation
Distribution patterns
DNA
Flow cytometry
Flow mapping
Fluorescence
Fluorescence in situ hybridization
Genomes
Karyotypes
Loci
Phalaenopsis
Phylogeny
Polymorphism
Transposition
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Summary:Abstract Phalaenopsis is a horticulturally important genus of c. 63 spp. native to Southeast Asia. Aiming to understand the genome differentiation and phylogenetic relationships in diploid Phalaenopsis spp., we investigated the nuclear DNA content by flow cytometry karyomorphology and mapped rDNA loci by fluorescence in situ hybridization to address genome differentiation. Most species have a chromosome complement of 2n = 38 (but have different karyotype compositions). Chromosome reduction is only observed in Phalaenopsis section Aphyllae (2n = 34 and 36). The genome sizes differ 6.3-fold, from 1C = 1.39 to 8.74 pg. Reconstruction of genome size indicates the genome size for the most recent common ancestor of Phalaenopsis subgenus Parishianae to be 3.92 pg/1C and for subgenus Phalaenopsis to be 2.42 pg/1C. The 45S rDNA sites are polymorphic and correlate positively with genome size, but 5S rDNA sites do not. Our results suggest independent evolutionary processes of genome size increase or decrease in each Phalaenopsis lineage. The polymorphism in the number of rDNA loci reveals that complex chromosomal rearrangements, e.g. gain or loss of repetitive DNA or chromosomes, inversion and/or transposition events, may have contributed to create the various karyotypes observed in Phalaenopsis spp.
ISSN:0024-4074
1095-8339
DOI:10.1093/botlinnean/box049