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Intrageneric phylogeny of Capsella (Brassicaceae) and the origin of the tetraploid C-bursa-pastoris based on chloroplast and nuclear DNA sequences
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Evolutionary Functional Genomics.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Evolutionary Functional Genomics.
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2006 (English)In: American Journal of Botany, ISSN 0002-9122, E-ISSN 1537-2197, Vol. 93, no 11, 1714-1724 p.Article in journal (Refereed) Published
Abstract [en]

Polyploidization, often accompanied by hybridization, has been of major importance in flowering plant evolution. Here we investigate the importance of these processes for the evolution of the tetraploid crucifer Capsella bursa-pastoris using DNA sequences from two chloroplast loci as well as from three nuclear low-copy genes. The near-absence of variation at the C. bursa-pastoris chloroplast markers suggests a single and recent origin of the tetraploid. However, despite supporting a single phylogeny, chloroplast data indicate that neither of the extant Capsella diploids is the maternal parent of the tetraploid. Combined with data from the three nuclear loci, our results do not lend support to previous hypotheses on the origin of C. bursa-pastoris as an allopolyploid between the diploids C. grandiflora and C. rubella or an autopolyploid of C. grandiflora. Nevertheless, for each locus, some of the C. bursa-pastoris accessions harbored C. rubella alleles, indicating that C. rubella contributed to the gene pool of C. bursa-pastoris, either through allopolyploid speciation or, more likely, through hybridization and introgression. To our knowledge, this study is the first of a wild, nonmodel plant genus that uses a combination of chloroplast and multiple low-copy nuclear loci for phylogenetic inference of polyploid evolution.

Place, publisher, year, edition, pages
2006. Vol. 93, no 11, 1714-1724 p.
Keyword [en]
Adh, Brassicaceae, Capsella, chloroplast DNA sequences, introgression, low-copy nuclear genes
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:uu:diva-96448DOI: 10.3732/ajb.93.11.1714ISI: 000242288400015OAI: oai:DiVA.org:uu-96448DiVA: diva2:171024
Available from: 2007-11-15 Created: 2007-11-15 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Evolution of Flowering Time in the Tetraploid Capsella bursa-pastoris (Brassicaceae)
Open this publication in new window or tab >>Evolution of Flowering Time in the Tetraploid Capsella bursa-pastoris (Brassicaceae)
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Although polyploidy is believed to be a major source of evolutionary novelty, few studies have examined the genetic basis of phenotypic variation in wild polyploids. In this thesis I have studied the genetic basis of flowering time variation in the wild tetraploid crucifer Capsella bursa-pastoris, as well as the evolutionary history of this species.

First, phylogenetic methods were employed to test hypotheses on the origin of C. bursa-pastoris. Based on DNA sequences from two chloroplast DNA loci and three independent nuclear genes, we found no support for the notion of C. bursa-pastoris as an autopolyploid of the diploid C. grandiflora, or an allopolyploid of C. grandiflora and C. rubella, even though some C. bursa-pastoris accessions shared alleles with C. rubella at nuclear loci. Using divergence population genetic methods, a larger sample of accessions and data for six duplicated nuclear genes, we found that allele sharing in sympatry was better explained by introgressive hybridization than by multiple origins of the tetraploid.

The genetic basis of flowering time variation was examined using three approaches. A gene expression microarray study revealed that early- and late-flowering accessions differ in circadian rhythm, as well as in the gibberellin pathway affecting flowering time. Second, two QTL (Quantitative Trait Loci) for flowering time map to duplicated linkage groups. Third, polymorphisms at the candidate genes CRYPTOCHROME1 (CRY1), in one of the QTL regions, and FLOWERING LOCUS C (FLC) are associated with natural flowering time variation. Different FLC splice site polymorphisms are associated with flowering time in samples from Western Eurasia and China. The CRY1 association is only found in Europe, where alleles introgressed from C. rubella have an effect on flowering time. In conclusion, duplicated genes, introgressive hybridization and splicing variation may all have played a role in the evolution of flowering time variation in C. bursa-pastoris.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2007. 40 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 367
Keyword
Biology, flowering time, homoeolog, hybridization, introgression, microarray, multiple origins, polyploid, QTL, Biologi
Identifiers
urn:nbn:se:uu:diva-8311 (URN)978-91-554-7024-1 (ISBN)
Public defence
2007-12-07, Lindahlsalen, EBC, Norbyvägen 18, Uppsala, 10:00 (English)
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Supervisors
Available from: 2007-11-15 Created: 2007-11-15 Last updated: 2009-10-30Bibliographically approved

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