AOBPreview originally published online on February 27, 2008
Annals of Botany 2008 101(7):919-927; doi:10.1093/aob/mcn026
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Genomic Origin and Organization of the Allopolyploid Primula egaliksensis Investigated by in situ Hybridization
1 Institut für Systematische Botanik & Zürich-Basel Plant Science Center
2 Institut für Pflanzenbiologie & Zürich-Basel Plant Science Center, Universität Zürich, Zollikerstrasse 107, CH-8008 Zürich, Switzerland
* For correspondence. E-mail alessia.guggisberg{at}systbot.uzh.ch
Received: 11 October 2007 Returned for revision: 20 December 2007 Accepted: 4 February 2008 Published electronically: 27 February 2008
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.
Key words: Diploidization, FISH, genome evolution, GISH, hybridization, ITS, polyploidy, Primula egaliksensis, 45S rDNA
CiteULike 
Connotea 
Del.icio.us What's this?
Related articles in Ann Bot:
- ContentSnapshots
Ann Bot 2008 101: NP.[Extract] [Full Text] - John Bryant takes a closer look at some of this month's Original Articles
- J. A. Bryant
Ann Bot 2008 101: NP.[Extract] [Full Text]
This article has been cited by other articles:
|
|
 |
|
  A. Guggisberg, G. Mansion, and E. Conti Disentangling Reticulate Evolution in an Arctic-Alpine Polyploid Complex Syst Biol, June 4, 2009; (2009) syp010v1. [Abstract] [Full Text] [PDF]
|
|