Biology subjects

Samwald, S.

Publications and source records attributed to Samwald, S..

5 recordsLinked to original sources

bioRxiv2026

Intronised fluorophores improve reporter output and biosensor expression in plants

Genetically encoded biosensors are central to plant cell biology, but low reporter signal can limit their use. Here, we developed modular intronised fluorophores to improve reporter output in transient and stable plant expression systems. Matched nuclear-localised triple mCitrine and mScarlet3 reporters were compared with and without introduced introns in Nicotiana benthamiana and Arabidopsis thaliana. Intronisation increased fluorescence, with the magnitude of enhancement depending on the fluorophore and expression context. Immunoblot analyses supported increased reporter accumulation. In Arabidopsis, intronised reporters driven by the tissue-specific SCARECROW promoter, produced stronger fluorescence signals that remained detectable farther from the root tip than non-intronised versions. Intronised versions of the abscisic acid (ABA) biosensor ABACUS2 retained ABA responsiveness and showed a lower frequency of reduced fluorescence between generations. These modular components provide a practical toolbox for improving fluorescent reporter detection and maintaining usable biosensor expression, supporting their application in plant cell biology and quantitative imaging.

plant biology↗

bioRxiv2026

A tunable receptor separates root barrier formation from nutrient signaling through ligand-perception states

In roots, the endodermis controls nutrient entry by forming a barrier known as the Casparian strip1-3. Yet how barrier-associated processes interface with systemic signaling remains unclear. Here, we show that the receptor kinase SCHENGEN3 links local barrier surveillance to systemic nutrient signaling, with outputs that depend on the effective state of ligand perception. Unlike in Arabidopsis thaliana, SCHENGEN3 activation in Lotus japonicus requires a distinct cellular competence state and cannot be triggered by exogenous ligands alone, revealing evolutionary divergence in pathway deployment. Cross-species complementation uncouples systemic nitrogen signaling from Casparian strip formation, while transcriptomic and phosphoproteomic analyses reveal largely non-overlapping signaling- and barrier-associated programs that differ between agar and agricultural soil conditions. Mechanistically, receptor-ligand comparisons, engineered receptor variants, and co-receptor mutant analyses show that systemic nitrogen signaling is retained in receptor-perception states that are insufficient to support full Casparian strip establishment. Together, these findings reveal how a shared receptor module can separate developmental and physiological outputs by linking receptor perception state to output specificity.

plant biology↗

bioRxiv2024

Putative neofunctionalization of a Poales-specific EXO70 clade

EXO70s are uniquely expanded in land plants compared to all other eukaryotic lineages. The functional implications of this expansion and diversification on the conserved role of EXO70 as a subunit of the octameric exocyst complex have remained unresolved. We previously demonstrated barley (Hordeum vulgare) EXO70FX12, a member of the monocot-specific EXO70FX clade, is required for resistance to wheat stripe rust in conjunction with the leucine-rich repeat receptor kinase (LRR-RK) HvPUR1. Through phylogenetic analysis, we identified unique features of the EXO70FX clade, leading us to hypothesize that this clade experienced neofunctionalization. Using structural predictions and protein-protein interaction assays, we demonstrate that HvEXO70FX12 lost the ability to serve as a subunit within the exocyst complex. We predict that the EXO70FX clade has largely lost exocyst association and represents a novel acquisition that emerged during Poales diversification for immunity.

plant biology↗

bioRxiv2022

Comparative phyloproteomics identifies conserved plasmodesmal proteins

Plasmodesmata connect neighbouring plant cells across the cell wall. They are cytosolic bridges, lined by the plasma membrane and traversed by endoplasmic reticulum to connect these cell components between cells and tissues. While plasmodesmata are notoriously difficult to extract, tissue fractionation and proteomic analyses have yielded valuable knowledge of their composition. Most proteomic profiles originate from cell suspension cultures in which simple plasmodesmata dominate and have been exclusively generated from dicotyledonous plant species. Here we have generated two novel proteomes to expand tissue and taxonomic representation of plasmodesmata: one from mature Arabidopsis leaves and one from the moss Physcomitrium patens. We have leveraged these and existing data to perform a comparative analysis that, owing to comparing proteomes from an expanded taxonomic tree, allowed us to identify conserved protein families that are associated with plasmodesmata that likely serve as core structural or functional components. Thus, we identified {beta}-1,3-glucanases, C2 lipid-binding proteins and tetraspanins as core plasmodesmal components, with proteins from P. patens and Arabidopsis maintaining plasmodesmal association across diverse species. Our approach has not only identified elements of a conserved, core plasmodesmal proteome, but also demonstrated the added power offered by comparative analysis. Conserved plasmodesmal proteins establish a basis upon which ancient plasmodesmal function can be further investigated to determine the essential roles these structures play in multicellular organism physiology in the green lineages.

plant biology↗

bioRxiv2019

Chitin perception in plasmodesmata identifies subcellular, context-specific immune signalling in plants

The plasma membrane (PM) that lines plasmodesmata has a distinct protein and lipid composition, underpinning specific regulation of these connections between cells. The plasmodesmal PM can integrate extracellular signals differently from the cellular PM, but it is not known how this specificity is established or how a single stimulus can trigger independent signalling cascades in neighbouring membrane domains. Here we have used the fungal elicitor chitin to investigate signal integration and responses at the plasmodesmal PM. We found that the plasmodesmal PM employs a receptor complex composed of the LysM receptors LYM2 and LYK4 which respectively change their location and interactions in response to chitin. Downstream, signalling is transmitted via a specific phosphorylation signature of an NADPH oxidase and localised callose synthesis that causes plasmodesmata closure. This demonstrates the plasmodesmal PM deploys both plasmodesmata-specific components and differential activation of PM-common components to independently integrate an immune signal.

plant biology↗