The establishment of Arabidopsis as the most important plant model has also brought other crucifer species into the spotlight of comparative research. While the genus Capsella has become a prominent crucifer model system, its closest relative has been overlooked. The unispecific genus Catolobus is native to temperate Eurasian woodlands, from eastern Europe to the Russian Far East. Here, we analyzed chromosome number, genome structure, intraspecific genetic variation, and habitat suitability of Catolobus pendulus throughout its range. Unexpectedly, all analyzed populations were hypotetraploid (2n = 30, ~330 Mb). Comparative cytogenomic analysis revealed that the Catolobus genome arose by a whole-genome duplication in a diploid genome resembling Ancestral Crucifer Karyotype (ACK, n = 8). In contrast to the much younger Capsella allotetraploid genomes, the presumably autotetraploid Catolobus genome (2n = 32) arose early after the Catolobus/Capsella divergence. Since its origin, the tetraploid Catolobus genome has undergone chromosomal rediploidization, including a reduction in chromosome number from 2n = 32 to 2n = 30. Diploidization occurred through end-to-end chromosome fusion and other chromosomal rearrangements affecting a total of six of 16 ancestral chromosomes. The hypotetraploid Catolobus cytotype expanded toward its present range, accompanied by some longitudinal genetic differentiation. The sister relationship between Catolobus and Capsella allows comparative studies of tetraploid genomes of contrasting ages and different degrees of genome diploidization.
- Klíčová slova
- Arabidopsis-related model systems, Brassicaceae, Cruciferae, Hyb-Seq, chromosome painting, diploidization, polyploidy, whole-genome duplication (WGD),
- Publikační typ
- časopisecké články MeSH
BACKGROUND AND AIMS: Cardamine occulta (Brassicaceae) is an octoploid weedy species (2n = 8x = 64) originated in Eastern Asia. It has been introduced to other continents including Europe and considered to be an invasive species. Despite its wide distribution, the polyploid origin of C. occulta remained unexplored. The feasibility of comparative chromosome painting (CCP) in crucifers allowed us to elucidate the origin and genome evolution in Cardamine species. We aimed to investigate the genome structure of C. occulta in comparison with its tetraploid (2n = 4x = 32, C. kokaiensis and C. scutata) and octoploid (2n = 8x = 64, C. dentipetala) relatives. METHODS: Genomic in situ hybridization (GISH) and large-scale CCP were applied to uncover the parental genomes and chromosome composition of the investigated Cardamine species. KEY RESULTS: All investigated species descended from a common ancestral Cardamine genome (n = 8), structurally resembling the Ancestral Crucifer Karyotype (n = 8), but differentiated by a translocation between chromosomes AK6 and AK8. Allotetraploid C. scutata originated by hybridization between two diploid species, C. parviflora and C. amara (2n = 2x = 16). By contrast, C. kokaiensis has an autotetraploid origin from a parental genome related to C. parviflora. Interestingly, octoploid C. occulta probably originated through hybridization between the tetraploids C. scutata and C. kokaiensis. The octoploid genome of C. dentipetala probably originated from C. scutata via autopolyploidization. Except for five species-specific centromere repositionings and one pericentric inversion post-dating the polyploidization events, the parental subgenomes remained stable in the tetra- and octoploids. CONCLUSIONS: Comparative genome structure, origin and evolutionary history was reconstructed in C. occulta and related species. For the first time, whole-genome cytogenomic maps were established for octoploid plants. Post-polyploid evolution in Asian Cardamine polyploids has not been associated with descending dysploidy and intergenomic rearrangements. The combination of different parental (sub)genomes adapted to distinct habitats provides an evolutionary advantage to newly formed polyploids by occupying new ecological niches.
- Klíčová slova
- Allopolyploidy, Asian Cardamine, Brassicaceae, GISH (genomic in situ hybridization), autopolyploidy, centromere repositioning, chromosome rearrangements, comparative chromosome painting, diploidization, genome collinearity, hybridization, invasive species,
- MeSH
- Brassicaceae * MeSH
- Cardamine * MeSH
- genom rostlinný MeSH
- lidé MeSH
- polyploidie MeSH
- zavlečené druhy MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Dálný východ MeSH
- Evropa MeSH
Quaternary climatic oscillations profoundly impacted temperate biodiversity. For many diverse yet undersampled areas, however, the consequences of this impact are still poorly known. In Europe, particular uncertainty surrounds the role of Balkans, a major hotspot of European diversity, in postglacial recolonization of more northerly areas, and the Carpathians, a debatable candidate for a northern 'cryptic' glacial refugium. Using genome-wide SNPs and microsatellites, we examined how the interplay of historical processes and niche shifts structured genetic diversity of diploid Arabidopsis arenosa, a little-known member of the plant model genus that occupies a wide niche range from sea level to alpine peaks across eastern temperate Europe. While the northern Balkans hosted one isolated endemic lineage, most of the genetic diversity was concentrated further north in the Pannonian Basin and the Carpathians, where it likely survived the last glaciation in northern refugia. Finally, a distinct postglacial environment in northern Europe was colonized by populations of admixed origin from the two Carpathian lineages. Niche differentiation along altitude-related bioclimatic gradients was the main trend in the phylogeny of A. arenosa. The most prominent niche shifts, however, characterized genetically only slightly divergent populations that expanded into narrowly defined alpine and northern coastal postglacial environments. Our study highlights the role of eastern central European mountains not only as refugia for unique temperate diversity but also sources for postglacial expansion into novel high-altitude and high-latitude niches. Knowledge of distinct genetic substructure of diploid A. arenosa also opens new opportunities for follow-up studies of this emerging model of evolutionary biology.
- Klíčová slova
- Arabidopsis, RADseq, approximate Bayesian computation, niche differentiation, phylogeography,
- MeSH
- Arabidopsis genetika MeSH
- ekosystém MeSH
- fylogeneze MeSH
- jednonukleotidový polymorfismus MeSH
- mikrosatelitní repetice MeSH
- populační genetika * MeSH
- refugium * MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Balkánský poloostrov MeSH
- východní Evropa MeSH
The nomenclature of Eastern Asian populations traditionally assigned to Cardamine flexuosa has remained unresolved since 2006, when they were found to be distinct from the European species Cardamine flexuosa. Apart from the informal designation "Asian Cardamine flexuosa", this taxon has also been reported under the names Cardamine flexuosa subsp. debilis or Cardamine hamiltonii. Here we determine its correct species name to be Cardamine occulta and present a nomenclatural survey of all relevant species names. A lectotype and epitype for Cardamine occulta and a neotype for the illegitimate name Cardamine debilis (replaced by Cardamine flexuosa subsp. debilis and Cardamine hamiltonii) are designated here. Cardamine occulta is a polyploid weed that most likely originated in Eastern Asia, but it has also been introduced to other continents, including Europe. Here data is presented on the first records of this invasive species in European countries. The first known record for Europe was made in Spain in 1993, and since then its occurrence has been reported from a number of European countries and regions as growing in irrigated anthropogenic habitats, such as paddy fields or flower beds, and exceptionally also in natural communities such as lake shores.
- Klíčová slova
- Asian Cardamine flexuosa, Brassicaceae, Cardamine flexuosa subsp. debilis, Cardamine hamiltonii, Cardamine occulta, China, Cruciferae, Europe, invasive species, typification,
- Publikační typ
- časopisecké články MeSH
