Biology subjects

van Velzen, R.

Publications and source records attributed to van Velzen, R..

7 recordsLinked to original sources

bioRxiv2026

Spatiotemporal dynamics of ethylene biosynthesis shape infection and nodule initiation in Medicago truncatula

Ethylene is a well-established negative regulator of nodulation, yet how ethylene biosynthesis and perception are spatially coordinated during early symbiotic signalling remains unresolved. Here, we investigate the dynamics of ethylene responses in Medicago truncatula using transcriptomics, promoter-reporter analyses, loss-of-function approaches and a synthetic reporter. We show that the activity of the ethylene-responsive EBSn reporter shifts from inner root tissues under non-symbiotic conditions to the outer cortex and epidermis following rhizobial inoculation, revealing a spatial reprogramming of ethylene signalling. Among the eight Medicago 1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACID SYNTHASE (ACS) genes, upon rhizobia application MtACS3 is induced in outer root cell layers, while MtACS10 is repressed in the inner cortex and pericycle, mirroring the shift in ethylene perception. Functional analysis demonstrates that MtACS10 restricts nodule initiation, whereas MtACS3 modulates infection thread number, prevents nodule clustering, and contributes to radial positioning of nodule primordia. Rhizobial induced ectopic ACS expression in the root interior counteracts MtACS10 repression and blocks nodulation, highlighting the requirement for spatially confined downregulation of ethylene biosynthesis. Together, these findings establish a framework in which localized shift in ethylene biosynthesis, mediated by distinct Medicago ACS genes, balances infection and organogenesis while co-defining the spatial limits of the root susceptible zone.

plant biology↗

bioRxiv2025

Two high-quality rose genomes underpin a novel Rosa pangenome to advance rose genomics, phylogenetics, and breeding

Rosa, belonging to the family Rosaceae, encompasses more than 150 species which are widely distributed in the northern hemisphere. Renowned for their beauty, roses are cultivated throughout the world for ornamental purposes and the production of essential oils and perfumes. Despite their cultural and commercial significance, the genomic resources of wild Rosa species have not been studied comprehensively, hampering the understanding of their genetic diversity, evolutionary history, and breeding potential. Here we report on high-quality de novo genomes for Rosa sericea and Rosa rugosa. By integrating these two de novo genomes with existing public genomic resources, we have built a Rosaceae panproteome and a Rosa pangenome (spanning wild, traditional garden, and modern rose lineages) using a De Bruijn graph (DBG)-based approach. A maximum likelihood (ML) phylogeny of 18 Rosa haplotypes based on 4,367 single-copy core homology groups (genes) provided robust evolutionary inference, confirming the basal position of R. sericea, and enabled a gene-based macrosynteny analysis across the pangenome. Our analyses revealed significant genomic diversity among species, extensive variation in core gene content, and lineage-specific transposable element (TE) expansion patterns that contribute to the variation in Rosa genome size and to species-specific adaptations. The pangenome also revealed biased diversification of homology groups potentially linked to phenotypic plasticity in Rosa. Specifically, our analysis of the rose scent-related gene family, NUDX1, uncovered its evolutionary trajectory in Rosa, in which TEs insertions provided putative novel regulatory elements that facilitated adaptive evolution in metabolic pathways. This pangenomic study deepens our understanding of the genetic diversity and evolution of traits within the Rosa genus. In addition, the findings lay the foundation for future efforts to understand the genetic mechanisms driving trait evolution, which can support rose breeding.

genomics↗

bioRxiv2024

Integrating target capture with whole genome sequencing of recent and natural history collections to explain the phylogeography of wild-growing and cultivated Cannabis

O_LICannabis has provided important and versatile services to humans for millennia. Domestication and subsequent dispersal have resulted in various landraces and cultivars. Unravelling the phylogeography of this genus poses considerable challenges due to its complex history. C_LIO_LIWe relied on a Hyb-Seq approach (combining target capture with shotgun sequencing), with the universal Angiosperms353 enrichment panel, to explore the genetic structure of wild-growing accessions and cultivars by implementing phylogenomic and population genomic workflows on the same Hyb-Seq data. C_LIO_LIOur findings support the treatment of Cannabis as a monotypic genus (C. sativa L.), structured into three main genetic groups--E Asia, Paleotropis, and Boreal--with clear phylogeographic signal despite significant levels of admixture. The E Asia group was sister to the Paleotropis and the Boreal groups. Individuals within the Paleotropis group could be further structured into three subgroups: Iranian Plateau, C & S China and Himalayas, and Indoafrica. Individuals from the Boreal group split into two subgroups: Eurosiberia and W Mongolia and Caucasus and Mediterranean. Hemp and drug-type landraces and cultivars consistently matched their putative geographic origin. C_LIO_LIThese findings enhance our understanding of the genetic patterns in Cannabis and provide a framework for future research into its current and past genetic diversity. C_LI

genomics↗

bioRxiv2024

Maroon rice genomic diversity reflects 350 years of colonial history

Maroons in Suriname and French Guiana descend from enslaved Africans who escaped the plantations during colonial times. Maroon farmers still cultivate a large rice diversity, their oldest staple crop. Maroon oral history and written records by colonial authorities provide contrasting perspectives on the origins of Maroon rice. Here, we integrated genomic ancestry analyses of 136 newly sequenced Maroon rice varieties with ethnobotanical and archival research to reconstruct the historical contexts associated with the introduction of rice varieties to the Guianas. We found that a large subset traces to West Africa, linked to the transatlantic slave trade (c.1530-1825). Maroons obtained other varieties from indentured laborers from Java (1890 onwards), USA rice breeders (1932 onwards), and Hmong refugees from the Vietnam War (1991). Furthermore, we found rice types never documented before, indicating Maroon farmers selected from crosses. Overall, our results demonstrate that the Maroon farming system prioritizes maintenance of a high stock diversity, which we posit reflects the expertise they inherited from their (African) ancestors. Ignored by agricultural modernization initiatives, Maroon farmers today are important custodians of a unique cultural heritage. Moreover, the genomic findings underline many Maroon stories about their past. This study hence demonstrates the power of cross-disciplinary crop research to reconstruct aspects of the human past for which historical records may be biased or incomplete. We anticipate that a similar study approach can be applied to other heirloom crops of (Indigenous) communities that may have preserved their history on their farms to reconstruct, acknowledge and honor the past.

genomics↗

bioRxiv2023

Natural gene variation in Cannabis sativa unveils a key region of cannabinoid synthase enzymes

Cannabinoids are well-known specialised metabolites from the plant Cannabis sativa L. (cannabis). They exhibit various therapeutical to intoxicating psychoactive effects and have potential for medicinal applications. Among the enzymes involved in cannabinoid biosynthesis, cannabinoid oxidocyclases such as the tetrahydrocannabinolic acid (THCA) synthase play a key role in determining cannabis chemotype. To improve our understanding of cannabinoid oxidocyclase structure-function relationship, we proposed a new approach to targeted mutagenesis. By reviewing cannabis natural variation, three cannabinoid oxidocyclase mutations (S355N, CONF, G376R) associated to atypical plant chemotypes were selected. In-vitro characterization of THCA synthase mutants demonstrated these mutations significantly impact enzyme activity, correlating with the associated chemotype: S355N nearly inactivated the THCA synthase, CONF impaired CBGA metabolization and altered product specificity, while G376R drastically reduced enzyme activity and altered product specificity. In-silico docking experiments permitted to model the successive steps of THCA synthase substrate metabolization, revealing that the three mutations hamper substrate binding. Collectively, our results demonstrated how plant diversity can be leveraged to guide enzyme targeted mutagenesis, highlighted a key region of cannabinoid oxidocyclases, and permitted the establishment of a new model of the THCA synthase catalytic mechanism. This provides new insights into enzyme function, which can ultimately help developing medicinal cannabis cultivars and cannabinoid biotechnological production.

molecular biology↗

bioRxiv2022

Global genomic analysis reveals the genetic origin and secondary invasion of fall armyworm in the Eastern hemisphere

The major plant pest fall armyworm (FAW), Spodoptera frugiperda, is native to the Americas and has colonized African and Asian countries in the Eastern hemisphere since 2016, causing severe damage to multiple agricultural crop species. However, the genetic origin of these invasive populations require more in-depth exploration. We analyzed genetic variation across FAW genomes of 153 newly sequenced individuals from Eastern hemisphere and 127 individuals mostly originating from the Americas. The global genetic structure of FAW shows that the FAW in American has experienced deep differentiation, largely consistent with the Z-chromosomal Tpi haplotypes commonly used to differentiate "corn-strain" and "rice-strain" populations. Results indicate that the invasive Eastern hemisphere populations are different from the American ones and have relatively homogeneous population structure, consistent with the common origin and recent spreading from Africa to Asia. Our analyses suggest that north-and central American "corn-strain" FAW are the most likely sources of the invasion into the Eastern hemisphere. Furthermore, evidence based on genomic, transcriptomic and mitochondrial haplotype network analysis suggest that there has been an earlier independent introduction of FAW into Africa that introgressed into the recent invasive population.

molecular biology↗

bioRxiv2020

Origin and evolution of the cannabinoid oxidocyclase gene family

Cannabis is an ancient crop representing a rapidly increasing legal market, especially for medicinal purposes. Medicinal and psychoactive effects of Cannabis rely on specific terpenophenolic ligands named cannabinoids. Recent whole-genome sequencing efforts have uncovered variation in multiple genes encoding the final steps in cannabinoid biosynthesis. However, the origin, evolution, and phylogenetic relationships of these cannabinoid oxidocyclase genes remain unclear. To elucidate these aspects we performed comparative genomic analyses of Cannabis, related genera within the Cannabaceae family, and selected outgroup species. Results show that cannabinoid oxidocyclase genes originated in the Cannabis lineage from within a larger gene expansion in the Cannabaceae family. Localization and divergence of oxidocyclase genes in the Cannabis genome revealed two main syntenic blocks, each comprising tandemly repeated cannabinoid oxidocyclase genes. By comparing these blocks with those in genomes from closely related species we propose an evolutionary model for the origin, neofunctionalization, duplication, and diversification of cannabinoid oxidocycloase genes. Based on phylogenetic meta-analyses, we propose a comprehensive classification of three main clades and seven subclades that is intended to aid unequivocal referencing and identification of cannabinoid oxidocyclase genes. Our data suggest that cannabinoid oxidocyclase gene copy number variation may have less functional relevance than previously thought. Instead, we propose that cannabinoid phenotype is primarily determined by presence/absence of single-copy genes. Increased sampling across Cannabis native geographic range is likely to uncover additional cannabinoid oxidocyclase gene sequence variation. Significance statementCannabis genome sequencing efforts have revealed extensive cannabinoid oxidocyclase gene variation. However, phylogenetic relationships and evolution of these genes remains unclear. Our meta analysis of currently available data reveals that these genes comprise three main clades and seven subclades that originated through Cannabis-specific gene duplication and divergence. Our new conceptual and evolutionary framework serves as a reference for future description and functional analyses of cannabinoid oxidocyclases.

evolutionary biology↗