Bartha, L. | bioRxiv Science

bioRxiv2026

Range wide analysis of genetic diversity and structure gives insights into Rosa gallica L. evolutionary history

Rosa gallica L., the French rose, is a perennial, tetraploid, heterozygous species that naturally propagates by seed and sucker. It occurs in the wild, primarily in Europe, and also exists as cultivated varieties. R. gallica cultivars were extensively bred and cultivated in France at the beginning of the 19th century. Although several hypotheses have been proposed regarding the species expansion based on historical records, none have been assessed using molecular data. Indeed, its genetic diversity has so far been investigated only at local or regional scales, hindering the identification of the evolutionary factors shaping its present-day distribution. Using 29 sequenced microsatellites, we genotyped a comprehensive sample of 1618 individuals, including wild R. gallica from 219 sites across the species range, rose cultivars, and specimens from other Rosa species. We then detected clonal lineages and characterized the range-wide genetic diversity and structure, aiming to disentangle the roles of natural and human factors in shaping the distribution of R. gallica, with particular focus on France. French diversity appears particularly structured compared to the rest of the range, suggesting multiple origins within France. Populations in South Alps, Central Eastern Europe, and Eastern France appear to have recolonized naturally from a single southern glacial refugium. In contrast, populations in the western part of France likely resulted from more recent natural or human-mediated dispersal. Finally, clonal lineages containing both wild and cultivated individuals were predominantly found in France, highlighting the role of human-mediated dispersal in 28 of the 98 French sites studied. These findings show that the present-day natural range of R. gallica was shaped primarily by post-glacial recolonization, but also reveal a contribution of human activities to its recent dispersal, particularly in France, where cultivated varieties were intensively bred and exchanged.

genetics↗

bioRxiv2021

Intact rDNA arrays of Potentilla-origin detected in Erythronium nucleus suggest recent eudicot-to-monocot horizontal transfer

The occurrence of horizontal gene transfer (HGT) in Eukarya is increasingly gaining recognition. Nuclear-to-nuclear jump of DNA between plant species at high phylogenetic distance and devoid of intimate association (e.g., parasitism) is still scarcely reported. Within eukaryotes, components of ribosomal DNA (rDNA) multigene family have been found to be horizontally transferred in protists, fungi and grasses. However, in neither case HGT occurred between phylogenetic families, nor the transferred rDNA remained tandemly arrayed and transcriptionally active in the recipient organism. This study aimed to characterize an alien eudicot-type of 45S nuclear rDNA, assumingly transferred horizontally to the genome of monocot European Erythronium (Liliaceae). Genome skimming coupled by PacBio HiFi sequencing of a BAC clone were applied to determine DNA sequence of the alien rDNA. A clear phylogenetic signal traced the origin of the alien rDNA of Erythronium back to the Argentea clade of Potentilla (Rosaceae) and deemed the transfer to have occurred in the common ancestor of E. dens-canis and E. caucasicum. Though being discontinuous, transferred rDNA preserved its general tandemly arrayed feature in the host organism. Southern blotting, molecular cytogenetics, and sequencing of a BAC clone derived from flow-sorted nuclei indicated integration of the alien rDNA into the recipients nuclear genome. Unprecedently, dicot-type alien rDNA was found to be transcribed in the monocot Erythronium albeit much less efficiently than the native counterpart. This study adds a new example to the growing list of naturally transgenic plants while holding the scientific community continually in suspense about the mode of DNA transfer. Significance StatementRibosomal DNA is an essential component of all cellular genomes. In plants, accidental movement of rDNA via horizontal gene transfer has only been reported in sexually incompatible grasses (monocots) where it involved non-functional rDNA units. In this study, we propose that evolutionary trajectories of eudicots and monocots were bypassed by the jump of rDNA from a Potentilla species (Rosaceae) to a common ancestor of Erythronium dens-canis and E. caucasicum (Liliaceae). The alien eudicot-type rDNA appeared relatively well conserved in the examined host Erythronium genome, being able to be expressed while preserving its general tandemly repeated feature, evidences that have no match in earlier literature.

plant biology↗