Biology subjects

Kersten, B.

Publications and source records attributed to Kersten, B..

4 recordsLinked to original sources

bioRxiv2026

Genomic analyses demonstrate the absence of genetic sex determination in the dioecious conifer Taxus baccata

Hundreds of plant lineages have independently evolved dioecy, i.e., separation of female and male flowers on different individuals. In all dioecious plants investigated at the molecular level to date, sex is determined genetically through a sex-determining region (SDR). SDRs have mostly been studied in angiosperms, although dioecy is relatively more common among gymnosperms. Here, we investigate sex determination in the gymnosperm Taxus baccata. We assembled four haplotype-resolved chromosome-level genomes for one female and one male tree, with an average size of 10.04 Gb, and generated resequencing data for 100 phenotypically sexed individuals. Strikingly, k-mer analyses, genome-wide association studies and differential coverage analyses demonstrate the absence of an SDR in the T. baccata genome. This indicates a non-genetic mechanism of sex determination, most likely via a sex-specific epiallele. Given that T. baccata is the first species studied among a large group of conifers, our findings suggest that such a mechanism might be widespread.

plant biology↗

bioRxiv2026

First report of genetic transformation and CRISPR/Cas12a-mediated gene editing of European beech (Fagus sylvatica L.)

Fagus sylvatica L. (European beech) is a dominant hardwood forest tree species across Central Europe, supporting diverse ecosystem services and forming the basis of a significant market for high-value timber. However, climate change increasingly threatens beech vitality and productivity, making molecular insights into its stress resilience and functional validation of underlying genes urgently needed. Here, we report a protocol for protoplast isolation from seedling leaves and demonstrate, for the first time, transient genetic transformation and CRISPR/Cas-mediated genome editing in F. sylvatica. PEG-mediated transformation was sequentially optimized, achieving efficiencies of 59 {+/-} 6.19% within distinct seasonal windows. Protoplast yield and transformation efficiency showed pronounced temporal variation throughout the year, indicating a strong seasonal influence on reproducibility of the workflow despite controlled growth conditions. A basic molecular toolkit for functional genomics and future biotechnological applications was established by testing a set of promoters and reporters. For proof-of-concept genome editing, we achieved 4.75 to 32.69% editing efficiencies in the PHYTOENE DESATURASE gene (FsPDS) using temperature-tolerant LbCas12a (ttLbCas12a). Although further optimization of transformation reproducibility and regeneration systems remains necessary, the presented protoplast platform provides a valuable foundation for transient functional assays and genome editing studies in this non-model tree species.

plant biology↗

bioRxiv2025

Provenance Legacies Override Species Effects in Shaping Oak Rhizosphere Microbiomes and Metabolomes

As climate change drives more frequent and intense drought-heat extremes, selecting drought-tolerant trees is crucial for future forest resilience. However, the role of tree-microbial associations for this key trait remains largely unclear. In this study, we investigated how geographic origin, species identity, and intrinsic water-use efficiency (iWUE) shape the rhizosphere microbiome and root-rhizosphere metabolome of pedunculate (Quercus robur) and sessile (Q. petraea) oaks. In a six-year common garden experiment, we analyzed trees from both species, each grown from seeds from two distinct geographic origins, the upper Rhine basin (URB) and the north-east German lowlands (NGL), differing in water availability, using 16S and ITS rRNA gene based metabarcoding and untargeted metabolomics. We found a consistent legacy effect of seed origin on the composition of the prokaryotic rhizosphere microbiome and the metabolome, whereas tree species had no significant impact. The bacterial family Pseudonocardiaceae was enriched at trees from the drier origin NGL, while Blastocatellaceae and Micromonosporaceae were positively associated with iWUE across samples. Higher iWUE was furthermore significantly correlated with lower prokaryotic diversity and shifts in {beta}-diversity, thereby linking a drought-adaptive host trait to the assembly of the belowground environment. Ellagic acid, a plant derived polyphenol associated with drought tolerance, was enriched in the drier origin NGL and linked to several prokaryotic taxa in correlation networks. The rhizosphere fungal community, however, was largely unaffected by origin or species. Solely fungal community evenness declined with increasing iWUE. Together, our findings suggest that ecotypic adaptation linked to origin can outweigh the effect of species-level traits in shaping the oak rhizosphere microbiome and metabolome. These findings emphasize that provenance-driven ecotypic adaptation can strongly influence plant-microbe interactions and underscore the need for provenance-aware selection and microbiome-informed assisted migration as strategies to strengthen forest drought resilience under global climate change.

ecology↗

bioRxiv2023

Identification of full-sibling families from natural single-tree ash progenies based on SSR markers and genome-wide SNPs

Common ash, Fraxinus excelsior, is threatened by the invasive pathogen Hymenoscyphus fraxineus, which causes ash dieback. The pathogen is rapidly spreading throughout Europe with severe ecological and economic consequences. Multiple studies have presented evidence for the existence of a small fraction of genotypes with low susceptibility. Such genotypes can be targets for natural and artificial selection to conserve F. excelsior and associated ecosystems. To resolve the genetic architecture of variation in susceptibility it is necessary to analyze segregating populations. Here we employed about 1,000 individuals of each of four single-tree progenies from potentially tolerant mother trees to identify full-sibling (full-sib) families. To this end, we first genotyped all 4,000 individuals and the four mothers with eight SSR markers. We then used the program Colony to predict full-sibs without knowledge of the paternal genotypes. For each single-tree progeny, Colony predicted dozens of full-sib families, ranging from 3-165 individuals. In a next step, 910 individuals assigned to full-sib families with more than 30 individuals were subjected to high-resolution genotyping using over one million genome-wide SNPs which were identified with Illumina low-coverage resequencing. Using these SNP genotyping data in principal component analyses we were able to assign individuals to full-sib families with high confidence. Together the analyses revealed five large families with 80-212 individuals. These can be used to generate genetic linkage maps and to perform quantitative trait locus analyses for ash dieback susceptibility or other traits to H. fraxineus or other traits. The elucidation of the genetic basis of natural variation in ash may support breeding and conservation efforts and may contribute to more robust forest ecosystems.

genomics↗