Biology subjects

von Arx, M.

Publications and source records attributed to von Arx, M..

7 recordsLinked to original sources

bioRxiv2026

Structural and functional insights into the role of Cysteine-Rich Receptor-Like Kinase 18 (CRK18) in Arabidopsis

Plants perceive and integrate diverse environmental signals through receptor kinase (RK) networks at the plasma membrane. Within this, Cysteine-Rich Receptor-Like Kinases (CRKs) constitute a large but not well-understood subfamily characterised by extracellular domains (ECDs) enriched in cysteine residues. CRKs have been implicated in plant responses to biotic and abiotic stress, as well as in developmental processes. Additionally, several CRKs have been proposed to act as redox sensors. Here, we investigate the homodimerization mechanism of Arabidopsis CRK18 and its regulation by redox conditions. By modulating pH and redox state, we assessed the stability and binding dynamics of the CRK18 ECD and its cysteine mutants. We also tested the plasma membrane localisation of all the cysteine mutants involved in the predicted disulfide bonds, and only CRK18C227A, C228A-ECD resembled the plasma membrane localization of wild-type CRK18. We combine co-immunoprecipitation, Forster resonance energy transfer-fluorescence lifetime imaging microscopy and microscale thermophoresis to quantify CRK18 self-association in planta and in vitro. Furthermore, we place CRK18 dimerization in a broader signalling context by identifying CRK18 interaction partners and CRK18-dependent signalling outputs. Using Arabidopsis CRK18 overexpression lines, we perform (phospho)proteomic and immunoprecipitation-mass spectrometry (IP-MS) analyses to map CRK18-centred signalling networks associated with stress-related responses. The constitutive activation of the CRK18 kinase domain and its interaction with many putative (cell wall) glycan-sensing RKs, including PERK15, suggest a regulatory role for CRK18. The absence of significant changes in the proteome and phosphoproteome of CRK18 overexpression lines in the absence of any trigger, and its restricted mobility after elicitation, suggest that CRK18 requires a stimulus for activation and possibly induces membrane microdomain reorganisation. This is in line with the infection assay with the nematode Heterodera schachtii, which causes modification and targeted damage to plant cell walls during infection, revealing that CRK18 acts as negative regulator of this process.

biochemistry↗

bioRxiv2026

Plasma membrane nanoscale dynamics of Arabidopsis leucine-rich repeat receptor kinase complexes

Plasma membrane-localized receptors operate as dynamic signaling complexes and integrative networks1-3, yet the spatial and temporal regulation of these interactions remain largely unknown. Here, by analyzing the components of a minimal Arabidopsis leucine-rich repeat receptor kinase network, we describe the differential diffusion and organization of receptor complex components and unveil the nanoscale spatial and temporal logic underlying the formation of receptor kinase complexes. The ligand-binding receptors FLS2 and BRI1, and the accessory receptor BIR3, are organized in plasma membrane nanodomains, within which the co-receptor BAK1 diffuses and is spatially arrested upon ligand perception. BAK1s spatial arrest relies on extracellular domain (ECD)-ECD interactions but does not require receptor complex activation. Mathematical modelling, single molecule imaging and bio-assays infer that accessory receptors maintain a dynamic pool of co-receptors in the vicinity of ligand-binding receptors to promote ligand-induced complex formation and signaling. We propose that ligand-induced receptor kinase complex formation is a deterministic process defined by the relative nanoscale spatial positioning of individual signaling and regulatory components.

cell biology↗

bioRxiv2025

Manipulation of REMORIN gene dosage affects salt signaling and tolerance in Arabidopsis thaliana

Salinity is among the most detrimental environmental plant stressors hampering growth, development and immunity. Its impact is increasing due to intensive agricultural practices and climate change. The molecular components linked to the early cellular and molecular events triggered by salt are mostly unknown. Here we show that genes encoding for members of the REMORIN proteins family exhibit dynamic temporal regulation following salt perception. Analogously to pattern-triggered immune signaling, we observed that salt rapidly induces the reorganization of REMORIN1.2 (REM1.2) into static plasma membrane nanodomains which colocalize with the actin-nucleating protein FORMIN 6. Overexpression of REM1.2 inhibits early signaling and late cell morphological responses to salt, defects which correlated with an increase in salt sensitivity. Our findings connect early salt-triggered signaling events to changes in cell architecture and root resilience and describe REMORIN nanodomains as a convergent articulation point in biotic and abiotic signaling pathways.

plant biology↗

bioRxiv2025

An ancient alkalinization factor informs Arabidopsis root development

The power of hydrogen (pH) regulates virtually all cellular activities. In both plants and animals, cell-to-cell variations in pH correlate with key developmental transitions1-5, yet the underlying regulators and associated functions remain elusive. Here, we report that members of the REMORIN (REM) protein family function as inhibitors of the H+-ATPases thereby promoting extracellular pH (pHe) alkalinization. This, in turn, regulates various cell surface processes, including steroid hormone signaling, and coordinates developmental transitions in the Arabidopsis thaliana root. Inhibition of H+-ATPases by REMs represents an evolutionary innovation that predates the origin of the root system itself. This study thus uncovers an ancient alkalinization mechanism co-opted by the root developmental program and infers that pHe patterning may have shaped morphogenesis evolution.

plant biology↗

bioRxiv2024

Photochromic reversion enables long-term tracking of single molecules in living plants.

Single-molecule imaging enables the observation of individual molecules in living cells (DEste et al., 2024; Kusumi et al., 2014; Lelek et al., 2021; Nguyen et al., 2023). In plants, however, the tracking of single molecules is typically limited to a few hundred milliseconds (Bayle et al., 2021; Gronnier et al., 2017; Hosy et al., 2015), precluding the observation of dynamic cellular processes at molecular resolution. Here, we describe photochromic reversion, an imaging modality that enables long-term single-molecule tracking of genetically encoded translational fusions. Using this approach, we achieve minute-long tracking of individual cell-surface receptors and reveal previously inaccessible dynamic spatial arrest events of single plasma membrane proteins. We further developed and benchmarked computational analysis of spatial arrests (CASTA), a machine learning-based tool that automatically detects and analyses spatial, temporal, and diffusional properties of these events, thereby enabling precise nanoscale kinetic measurements. Together, these advances provide a powerful framework for deciphering the principles governing membrane dynamics and function.

cell biology↗

bioRxiv2024

A RALF-Brassinosteroid morpho-signaling circuit regulates Arabidopsis hypocotyl cell shape

Plant cells survey and modulate their cell wall to control their shape and anisotropic growth. Signaling mediated by the plant steroid hormones brassinosteroids (BR) plays a central role in coordinating cell wall status and cell growth, and alterations in the cell wall - BR feedback loop leads to life-threatening defects in tissue and cellular integrity. How the status of the cell wall is relayed to BR signaling remains largely unclear. Increasing evidence shows that RAPID ALKALANIZATION FACTORs (RALFs), a class of secreted peptides, play structural and signaling roles at the cell surface. Here we show that perception of RALF23 promotes the formation and signaling of the main BR receptor complex formed by BRASSINOSTEROID INSENSITIVE 1 (BRI1) and BRI1-BRASSINOSTEROID INSENSITIVE1-BRASSINOSTEROID-ASSOCIATED KINASE 1 (BAK1). The loss of the plasma membrane-localized RALF receptor complex FERONIA (FER)-LORELEI LIKE GPI-anchor protein 1 (LLG1) leads to defects in cell expansion and anisotropy, as well as uncontrolled BRI1-BAK1 complex formation and signaling. RALF23 bioactivity relies on pectin status and its perception induces changes in pectin composition and the activity of pectin-modifying enzymes. Our observations suggest a model in which RALF23 functions as a cell wall-informed signaling cue initiating a feedback loop that solicits BR signaling, modifies the cell wall, and coordinates cell morphogenesis. Highlights-The RALF receptor complex FER-LLG1 regulates cell anisotropic growth -RALF23 promotes BRI1-BAK1 complex formation and signaling -RALF23 functions as a cell wall-informed and wall-modifying signaling cue

plant biology↗

bioRxiv2022

SciCV, the Swiss National Science Foundation's new CV format

BackgroundThe Swiss National Science Foundation (SNSF) tested a new CV format called SciCV to encourage fair, DORA-compliant assessment of grant applicants. It was developed in close collaboration with the academic evaluation community and international experts, introduced through detailed change management and finally tested in its utility by an independent research team of the Center for Science and Technology Studies Leiden (CWTS). MethodsWe present the development of the SciCV pilot and its evaluation by the CWTS research group. The analysis comprised both quantitative and qualitative methods, with (i) surveys and semi-structured interviews with applicants and reviewers, (ii) text analysis of the narrative elements of SciCV, and (iii) participant observation in ten evaluation panel meetings. ResultsNarrative elements and the inclusion of the academic age were rated as most useful new CV elements, while the inclusion of two metrics, the h-index and the relative citation ratio, were received more critically. The omission of a full publication list had similar numbers of supporters and opponents among applicants and reviewers. Less experienced and junior applicants and reviewers rated the new format generally more positively than more senior applicants and reviewers. The text analysis of narrative elements yielded no significant gender specific differences. The participant observation revealed that the new elements in SciCV broadened the information base used in the evaluation of applicants but did not fundamentally alter traditional, publication-centred evaluation practices. ConclusionSciCV was a relevant and successful initiative for the SNSF, which showed that the implementation of a new, well-structured CV format is not only feasible but also something that many stakeholders welcome.The extensive experience and results obtained during the change process formed the basis for the development of SciCV 2.0 at the SNSF. It also offers a basis and guidance for other funding organisations planning similar initiatives.

scientific communication and education↗