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Genomic origin and organization of the allopolyploid Primula egaliksensis investigated by in situ hybridization


Guggisberg, A; Baroux, C; Grossniklaus, U; Conti, E (2008). Genomic origin and organization of the allopolyploid Primula egaliksensis investigated by in situ hybridization. Annals of Botany, 101(7):919-927.

Abstract

BACKGROUND AND AIMS: Earlier studies have suggested that the tetraploid Primula egaliksensis (2n = 40) originated from hybridization between the diploids P. mistassinica (2n = 18) and P. nutans (2n = 22), which were hypothesized to be the maternal and paternal parent, respectively. The present paper is aimed at verifying the hybrid nature of P. egaliksensis using cytogenetic tools, and to investigate the extent to which the parental genomes have undergone genomic reorganization. METHODS: Genomic in situ hybridization (GISH) and fluorescent in situ hybridization (FISH) with ribosomal DNA (rDNA) probes, together with sequencing of the internal transcribed spacer (ITS) region of the rDNA, were used to identify the origin of P. egaliksensis and to explore its genomic organization, particularly at rDNA loci. KEY RESULTS: GISH showed that P. egaliksensis inherited all chromosomes from P. mistassinica and P. nutans and did not reveal major intergenomic rearrangements between the parental genomes (e.g. interchromosomal translocations). However, karyological comparisons and FISH experiments suggested small-scale rearrangements, particularly at rDNA sites. Primula egaliksensis lacked the ITS-bearing heterochromatic knobs characteristic of the maternal parent P. mistassinica and maintained only the rDNA loci of P. nutans. These results corroborated sequence data indicating that most ITS sequences of P. egaliksensis were of the paternal repeat type. CONCLUSIONS: The lack of major rearrangements may be a consequence of the considerable genetic divergence between the putative parents, while the rapid elimination of the ITS repeats from the maternal progenitor may be explained by the subterminal location of ITS loci or a potential role of nucleolar dominance in chromosome stabilization. These small-scale rearrangements may be indicative of genome diploidization, but further investigations are needed to confirm this assumption.

Abstract

BACKGROUND AND AIMS: Earlier studies have suggested that the tetraploid Primula egaliksensis (2n = 40) originated from hybridization between the diploids P. mistassinica (2n = 18) and P. nutans (2n = 22), which were hypothesized to be the maternal and paternal parent, respectively. The present paper is aimed at verifying the hybrid nature of P. egaliksensis using cytogenetic tools, and to investigate the extent to which the parental genomes have undergone genomic reorganization. METHODS: Genomic in situ hybridization (GISH) and fluorescent in situ hybridization (FISH) with ribosomal DNA (rDNA) probes, together with sequencing of the internal transcribed spacer (ITS) region of the rDNA, were used to identify the origin of P. egaliksensis and to explore its genomic organization, particularly at rDNA loci. KEY RESULTS: GISH showed that P. egaliksensis inherited all chromosomes from P. mistassinica and P. nutans and did not reveal major intergenomic rearrangements between the parental genomes (e.g. interchromosomal translocations). However, karyological comparisons and FISH experiments suggested small-scale rearrangements, particularly at rDNA sites. Primula egaliksensis lacked the ITS-bearing heterochromatic knobs characteristic of the maternal parent P. mistassinica and maintained only the rDNA loci of P. nutans. These results corroborated sequence data indicating that most ITS sequences of P. egaliksensis were of the paternal repeat type. CONCLUSIONS: The lack of major rearrangements may be a consequence of the considerable genetic divergence between the putative parents, while the rapid elimination of the ITS repeats from the maternal progenitor may be explained by the subterminal location of ITS loci or a potential role of nucleolar dominance in chromosome stabilization. These small-scale rearrangements may be indicative of genome diploidization, but further investigations are needed to confirm this assumption.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Systematic and Evolutionary Botany
07 Faculty of Science > Department of Plant and Microbial Biology
Dewey Decimal Classification:580 Plants (Botany)
Language:English
Date:May 2008
Deposited On:27 Jan 2009 20:57
Last Modified:21 Nov 2017 13:53
Publisher:Oxford University Press
ISSN:0305-7364
Publisher DOI:https://doi.org/10.1093/aob/mcn026
PubMed ID:18308718

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