Genomic Origin and Organization of the Allopolyploid Primula egaliksensis Investigated by in situ Hybridization

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 assumptio

Frische Forschung mit trockenen Pflanzen: Recherche botanique – du neuf avec du vieux

Die vier grössten Schweizer Herbarien beherbergen knapp 12 Millionen Belege. In diesem Artikel zeigen wir Beispiele, wie Pflanzen von gestern in der Forschung von heute genutzt werden. Les quatre plus grands herbiers suisses rassemblent près de 12 millions de spécimens. Dans cet article, nous montrons comment les échantillons d’autrefois sont utilisés dans la recherche d’aujourd’hui

Allopolyploid origin of the mediterranean endemic, Centaurium bianoris (Gentianaceae), inferred by molecular markers

International audienceCentaurium bianoris (Gentianaceae) is restricted to Majorca, the main island of the Balearic Archipelago. This tetraploid species is characterised by salmon-coloured corollas (var. bianoris), but pink (var. roseum) and yellow (var. sulfureum) varieties have also been described. An allopolyploid origin has been proposed between the diploids C. maritimum (yellow flowers) and C. tenuiflorum var. acutiflorum (pink flowers), both occurring on Majorca and in other places of the Mediterranean basin. In this study, we tested the proposed hybrid origin of C. bianoris by using RAPD fingerprinting, and both direct and cloned sequences of the nuclear ribosomal ITS, and the chloroplast trnLF regions. Our molecular data confirmed the hypothesis of an allotetraploid origin of C. bianoris via hybridisation between C. tenuiflorum and C. maritimum, the latter being the maternal parent. The so-called varieties roseum and sulfureum appeared to be only floral morphs that may have arisen via genomic processes such as gene silencing. Hybridisation is probably the cause of the ITS sequence polymorphism observed in C. bianoris, whereas backcrosses with either parent may be responsible for the apparent bidirectional homogenisation observed in ITS clones. Finally, the polyphyletic behaviour of C. bianoris on the ITS cladogram, combined with the differential rates of homogenisation observed in ITS sequences, may denote a recurrent origin for that taxon. This result contrasts with the narrow distribution of C. bianoris, compared to that of its diploid parents, suggesting instead a single origin for this hybrid

Genetically Based Trait Differentiation but Lack of Trade-offs between Stress Tolerance and Performance in Introduced Canada Thistle

Trade-offs between performance and tolerance of abiotic and biotic stress have been proposed to explain both the success of invasive species and frequently observed size differences between native and introduced populations. Canada thistle seeds collected from across the introduced North American and the native European range were grown in benign and stressful conditions (nutrient stress, shading, simulated herbivory, drought, and mowing), to evaluate whether native and introduced individuals differ in performance or stress tolerance. An additional experiment assessed the strength of maternal effects by comparing plants derived from field-collected seeds with those derived from clones grown in the glasshouse. Introduced populations tended to be larger in size, but no trade-off of stress tolerance with performance was detected; introduced populations had either superior performance or equivalent trait values and survivorship in the treatment common gardens. We also detected evidence of parallel latitudinal clines of some traits in both the native and introduced ranges and associations with climate variables in some treatments, consistent with recent climate adaptation within the introduced range. Our results are consistent with rapid adaptation of introduced populations, but, contrary to predictions, the evolution of invasive traits did not come at the cost of reduced stress tolerance

280808-2

Collection ID: 280808-2 | Taxon: Cirsium arvense (L.) Scop. | Common name: Canada thistle | Collection locality: Female plant, Lugoj, Romania (latitude 45.65, longitude 21.95) | Plant tissues employed for EST library development: Leaves | Library type: Standard | Sequence type: Illumin

KN-ON

Collection ID: KN-ON | Taxon: Cirsium arvense (L.) Scop. | Common name: Canada thistle | Collection locality: Male plant, Richmond Hill, ON, Canada (latitude 43.95, longitude -79.56) | Plant tissues employed for EST library development: Leaves | Library type: Standard | Sequence type: Illumin

The genomic basis of adaptation to calcareous and siliceous soils in Arabidopsis lyrata

ISSN:0962-1083ISSN:1365-294

Genomic Origin and Organization of the Allopolyploid Primula egaliksensis Investigated by in situ Hybridization

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