Articles
MICROSATELLITE AND RDNA ANALYSIS REVEAL UNIQUE REPRODUCTION IN DOGROSES
Article number
859_28
Pages
247 – 253
Language
English
Abstract
The taxonomically complex dogroses (Rosa sect. Caninae) are mostly pentaploid (2N=5x=35) but only seven bivalents are formed in the first meiotic division.
The remaining chromosomes form univalents and occur only in eggcells where they are transmitted through the seed parent.
An allopolyploid origin of dogroses was suggested many years ago but genomic configuration remained a mystery until the Microsatellite Allele Counting – based on Peak Ratios (MAC-PR) technique was developed.
Using this approach for determination of microsatellite allele copy number in polyploids, analyses of different dogrose species and offspring from controlled crosses, showed that bivalent formation involves one biparentally inherited, highly homozygous diploid genome.
The maternally transmitted univalent genomes are instead highly differentiated within the genotype and also between taxa.
Later, several rRNA gene (rDNA) families were identified from extensive cloning analysis of the ITS-1 region.
The beta family occurs in each of the investigated dogrose species, whereas the others occur only in some species.
Samples of pollen DNA contain proportionally more of the beta family, suggesting that this resides mainly on the bivalents.
Expression analyses have shown that the beta family is considerably upregulated compared to other rRNA families, suggesting that the univalent genomes may undergo frequent epigenetic silencing.
The remaining chromosomes form univalents and occur only in eggcells where they are transmitted through the seed parent.
An allopolyploid origin of dogroses was suggested many years ago but genomic configuration remained a mystery until the Microsatellite Allele Counting – based on Peak Ratios (MAC-PR) technique was developed.
Using this approach for determination of microsatellite allele copy number in polyploids, analyses of different dogrose species and offspring from controlled crosses, showed that bivalent formation involves one biparentally inherited, highly homozygous diploid genome.
The maternally transmitted univalent genomes are instead highly differentiated within the genotype and also between taxa.
Later, several rRNA gene (rDNA) families were identified from extensive cloning analysis of the ITS-1 region.
The beta family occurs in each of the investigated dogrose species, whereas the others occur only in some species.
Samples of pollen DNA contain proportionally more of the beta family, suggesting that this resides mainly on the bivalents.
Expression analyses have shown that the beta family is considerably upregulated compared to other rRNA families, suggesting that the univalent genomes may undergo frequent epigenetic silencing.
Authors
H. Nybom, G. Werlemark, L. Khaitová, A. Kovařík, D.G. Esselink
Keywords
breeding system, Caninae, meiosis, polyploidy, rRNA genes, Rosa
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