Biology subjects

Kleine-Vehn, J.

Publications and source records attributed to Kleine-Vehn, J..

17 recordsLinked to original sources

bioRxiv2026

Cytokinin regulates the gravitropic setpoint angle of seminal roots in barley and wheat

Plant root growth angle determines the spatial distribution of roots in soil and thereby influences access to water and nutrients when these resources are heterogeneously distributed. In barley, multiple seminal roots emerge at distinct gravitropic setpoint angles (GSAs) and they reliably re-establish their characteristic growth angles following reorientation, indicating robust intrinsic control. However, the molecular basis underlying GSA variation among roots within a single root system remains unknown. Here, we combined individual root type-specific transcriptomics with laser-capture microdissection to profile gravity-responsive zones (root cap, meristem, and elongation zone). We identified two CYTOKININ OXIDASE/DEHYDROGENASE (CKX) genes whose expression in the root cap was associated with root-specific GSA. Functional analysis showed that ckx mutants, which show higher cytokinin levels, exhibit significantly steeper seminal root GSAs, implicating cytokinin catabolism in root angle regulation. Consistent with this, exogenous cytokinin treatment induced a dose-dependent steepening in root angle in barley. Analyses of gravitropic curvature after gravistimulation further showed that ckx mutants exhibit altered gravitropic responses, indicating that CKX-mediated regulation of the root angle depends on gravity-responsive pathways. Notably, GSA-associated CKX expression patterns and cytokinin-dependent root angle responses were also observed in wheat, suggesting a conservation of this mechanism across cereals. Together, these findings identify cytokinin as a key regulator of root specific setpoint angles within a root system architecture, with potential implications for optimizing crop resource acquisition and yield.

plant biology↗

bioRxiv2026

Mechanical coordination of counter-gradient growth maintains organ curvature in apical hooks

How growing tissues convert mechanical tension into signals that stabilize form remains a central question in morphogenesis. Curved organ shapes in plants arise from differential growth, yet how such curvature is actively maintained while organs continuously grow remains poorly understood. In etiolated seedlings, the apical hook provides a tractable model to dissect this process, as its curvature is stably maintained over extended periods despite ongoing cell expansion. Using quantitative imaging and computational modeling, we show that antagonistic growth gradients at apical and basal regions are both necessary and sufficient to maintain hook curvature, with cuticle integrity being critical for establishing these counter-gradients. Mechanical cues linked to cuticle structure, coupled with apoplastic reactive oxygen species (ROS), coordinate cellular growth anisotropy, and disruptions in cuticle biosynthesis trigger defective hook development. These findings reveal that the apical hook curve maintenance is not a simple switch between growth promotion and repression, but a highly dynamic, tightly regulated process where mechanical and biochemical signals coordinate organ-scale morphogenesis, fundamentally reshaping how we understand developmental growth.

plant biology↗

bioRxiv2025

ERAD machinery controls the conditional turnover of PIN-LIKES in plants

Auxin is a crucial phytohormone that regulates plant development and facilitates dynamic responses to environmental changes through subcellular control mechanisms. PIN-LIKES (PILS) are auxin transport facilitators at the endoplasmic reticulum (ER) that mediate nuclear auxin abundance and signalling. While the posttranslational regulation of PILS is important for acclimating growth responses, the molecular mechanisms involved remain largely unknown. This study demonstrates that components of the ER-associated degradation (ERAD) machinery regulate the proteasome-dependent degradation of functional PILS proteins under non-stressed conditions. We further reveal that both internal and external signals utilise the ERAD complex to differentially modulate the turnover rates of PILS proteins. Our findings uncover an additional physiological role of the ERAD complex in regulating PILS protein turnover. This finding uncovers the interplay between protein homeostasis at the ER and growth regulation, opening new molecular avenues into how plants acclimate to internal and external cues.

plant biology↗

bioRxiv2024

Two distinct oscillatory auxin signals define the plasticity of lateral rooting in Arabidopsis thaliana

The phytohormone auxin defines lateral root pre-branch sites (PBS) in the growing primary root tip. How PBS contribute to the plasticity of the root system architecture remains incompletely understood1,2,3,4. Here, we reveal in the model plant Arabidopsis thaliana that two distinct oscillatory systems for the phytohormone auxin coordinate the spatial and temporal identity of PBS, jointly defining the lateral root density. We followed auxin signalling dynamics for days and thereby detected a systemic auxin signal oscillating along the mature primary root, where PBS potentially form functional root branches. While a previously proposed local oscillatory auxin zone spatially primes the PBS in the growing root tip, we reveal that the systemic oscillatory auxin signal temporally controls the auxin-dependent identity of these PBS. Light perception in the shoot defines the strength of the systemic auxin signal and thereby controls the auxin-reliant ability of PBS to develop into lateral roots. Moreover, PHYB and CRY1 mediate the light-dependent integration of other environmental signals, such as ambient temperature, into the control systemic auxin signalling and lateral root density. Our work reveals how two spatially distinct oscillatory auxin signals define the plasticity of plant root development in response to fluctuating conditions.

plant biology↗

bioRxiv2023

Pectin methylesterase activity is required for RALF1 peptide signalling output

The extracellular matrix plays an integrative role in cellular responses in plants, but its contribution to the signalling of extracellular ligands largely remains to be explored. RAPID ALKALINIZATION FACTORs (RALFs) are extracellular peptide hormones that play pivotal roles in various physiological processes. Here, we address a crucial connection between the de-methylesterification machinery of the cell wall component pectin and RALF1 activity. Pectin is a polysaccharide, contributing to the structural integrity of the cell wall. Our data illustrate that the pharmacological and genetic interference with PECTIN METHYL ESTERASEs (PMEs) abolishes RALF1-induced root growth repression. Our data suggest that positively charged RALF1 peptides bind negatively charged, de-methylesterified pectin with high avidity. We illustrate that the RALF1 association with de-methylesterified pectin is required for its FERONIA-dependent perception, contributing to the control of the extracellular matrix and the regulation of plasma membrane dynamics. Notably, this mode of action is independent of the FER-dependent extracellular matrix sensing mechanism provided by FER interaction with the Leucine-Rich Repeat Extensin (LRX) proteins. We propose that the methylation status of pectin acts as a contextualizing signalling scaffold for RALF peptides, linking extracellular matrix dynamics to peptide hormone-mediated responses.

plant biology↗

bioRxiv2023

Endoplasmic-Reticulum stress controls PIN-LIKES abundance and thereby growth adaptation

Extreme environmental conditions eventually limit plant growth (1, 2). Here we reveal an unprecedented mechanism that enables multiple external cues to get integrated into auxin-dependent growth programs in Arabidopsis thaliana. Our forward genetics approach on dark grown hypocotyls uncovered that an imbalance in membrane lipids enhances the protein abundance of PIN-LIKES (PILS) (3-5) auxin transport facilitators at the endoplasmic reticulum (ER), which thereby limits nuclear auxin signaling and growth rates. We show that this subcellular response relates to ER stress signaling, which directly impacts on PILS protein turnover in a tissue-dependent manner. This mechanism allows PILS proteins to integrate environmental input with phytohormone auxin signaling, contributing to stress-induced growth adaptation in plants.

plant biology↗

bioRxiv2022

PILS proteins provide a homeostatic feedback on auxin signaling output

Auxin is a crucial regulator of plant growth and development. Multiple internal and external signals converge at the regulation of auxin metabolism, intercellular transport, and signaling (Pernisova and Vernoux, 2021; Anfang and Shani, 2021). Considering this complexity, it remains largely unknown how plant cells monitor and ensure the homeostasis of auxin responses. PIN-LIKES (PILS) intracellular auxin transport facilitators at the endoplasmic reticulum (ER) are suitable candidates to buffer cellular auxin responses, because they limit nuclear abundance and signaling of auxin (Barbez et al., 2012; Beziat et al., 2017; Feraru et al., 2019; Sun et al., 2020). We used forward genetics to identify mechanisms that define the PILS6 protein abundance and thereby auxin signaling outputs. We screened for gloomy and shiny pils (gasp) mutants that define the levels of PILS6-GFP under a constitutive promoter. In this study, we show that GASP1 encodes for an uncharacterized RING/U-box superfamily protein and impacts on auxin signaling output. We conclude that the low auxin signaling in gasp1 mutants correlates with reduced abundance of PILS proteins, such as PILS5 and PILS6, which consequently balances auxin-related phenotypes. In agreement, we show that high and low auxin conditions increase and reduce PILS6 protein levels, respectively. Accordingly, non-optimum auxin concentrations are buffered by alterations in PILS6 abundance, consequently leading to homeostatic auxin output regulation. We envision that this feedback mechanism provides robustness to auxin-dependent plant development.

plant biology↗

bioRxiv2022

Multiphasic calcium signatures in the cytosol and nucleus of Lotus japonicus roots unlock the early discrimination of fungal signals

The recognition of different microbe-associated molecular patterns in the rhizosphere triggers in the plant root the activation of either an immune response or an accommodation program. In both types of responses, Ca2+ is a crucial intracellular messenger, mediating the early stages of the respective signalling pathways. In this work, we analysed the cytosolic and nuclear Ca2+ changes activated by a set of chitin-related oligomers in different genetic backgrounds of Lotus japonicus roots by using specifically targeted aequorin-based Ca2+ reporters. By means of pharmacological and genetic approaches, we dissected the Ca2+ signal into two temporally distinct components: a rapid initial transient, followed by a longer and milder elevation in Ca2+ concentration. Taking advantage of a complementary analysis using a cameleon-based bioassay in Medicago truncatula root organ cultures, we showed that the second phase can be interpreted as the Ca2+ spiking that is widely described in response to the perception of symbiotic signals. By contrast, the rapid first phase, critically dependent on elicitor concentration, was found to correlate with the activation of plant immunity marker genes. Overall, our study provides novel clues to a better understanding of the subtle boundaries between symbiotic and immunity responses in root-fungus interactions. HighlightIntracellular calcium changes induced in Lotus japonicus roots by fungal signals were dissected in two separate phases, relying on distinct genetic programs and differentially mediating plant symbiotic or immunity responses.

plant biology↗

bioRxiv2021

Endocytic Trafficking Promotes Vacuolar Enlargements for Fast Cell Expansion Rates in Plants

The vacuole has a space-filling function, allowing a particularly rapid plant cell expansion with very little increase in cytosolic content (Lofke et al., 2015; Scheuring et al., 2016; Dunser et al., 2019). Despite its importance for cell size determination in plants, very little is known about the mechanisms that define vacuolar size. Here we show that the cellular and vacuolar size expansions are coordinated. By developing a pharmacological tool, we enabled the investigation of membrane delivery to the vacuole during cellular expansion. Counterintuitively, our data reveal that endocytic trafficking from the plasma membrane to the vacuole is enhanced in the course of rapid root cell expansion. While this "compromise" mechanism may theoretically at first decelerate cell surface enlargements, it fuels vacuolar expansion and, thereby, ensures the coordinated augmentation of vacuolar occupancy in dynamically expanding plant cells.

plant biology↗

bioRxiv2020

FERONIA regulates FLS2 plasma membrane nanoscale dynamics to modulate plant immune signaling

Spatial partitioning is a propensity of biological systems orchestrating cell activities in space and time. The dynamic regulation of plasma membrane nano-environments has recently emerged as a key fundamental aspect of plant signaling, but the molecular components governing it are still mostly unclear. The receptor kinase FERONIA (FER) controls complex formation of the immune receptor kinase FLAGELLIN SENSING 2 (FLS2) with its co-receptor BRASSINOSTEROID INSENSITIVE 1-ASSOCIATED KINASE 1 (BAK1), and this function is inhibited by the FER ligand RAPID ALKALANIZATION FACTOR 23 (RALF23). Here, we show that FER regulates the plasma membrane nanoscale organization of FLS2 and BAK1. Our study demonstrates that akin to FER, leucine-rich repeat (LRR) extensin (LRXs) proteins contribute to RALF23 responsiveness, regulate BAK1 nanoscale organization and immune signaling. Furthermore, RALF23 perception leads to rapid modulation of FLS2 and BAK1 nanoscale organization and its inhibitory activity on immune signaling relies on FER kinase activity. Our results suggest that perception of RALF peptides by FER and LRXs actively modulates the plasma membrane nanoscale landscape to regulate cell surface signaling by other receptor kinases.

plant biology↗

bioRxiv2019

Auxin-dependent xyloglucan remodelling defines differential tissue expansion in Arabidopsis thaliana

Size control is a fundamental question in biology, showing incremental complexity in case of plants whose cells possess a rigid cell wall. The phytohormone auxin is a vital growth regulator with central importance for differential growth control. Here we show that growth inducing and repressing auxin conditions correlate with reduced and enhanced complexity of extracellular xyloglucans, respectively. In agreement, genetic interference with xyloglucan complexity distinctly modulates auxin-dependent differential growth rates. Our work proposes that an auxin-dependent, spatially defined effect on xyloglucan structure and its effect on cell wall mechanics specify differential, gravitropic hypocotyl growth.

plant biology↗

bioRxiv2019

NET4 modulates the compactness of vacuoles in Arabidopsis thaliana

The dimension of the plants largest organelle - the vacuole, plays a major role in defining cellular elongation rates. The morphology of the vacuole is controlled by the actin cytoskeleton but the mechanistic connection between them remains largely elusive. Recently, the NETWORKED (NET) family of membrane-associated, actin-binding proteins has been identified and represent potential candidates to impact on vacuolar morphology. Here, we show that NET4A localizes to highly constricted regions in the vacuolar membrane and contributes to the compactness of the vacuole. Using genetic interference, we found that deregulation of NET4 abundance impacts on vacuole morphogenesis and overexpression leads to more compact vacuoles. We moreover show that the NET4A-induced changes in vacuolar shape correlates with reduced cellular and organ growth in Arabidopsis thaliana. Our results demonstrate that NET4 modulates the compactness of vacuoles and reveal higher complexity in the regulation of actin-reliant vacuolar morphology.

plant biology↗

bioRxiv2019

Brassinosteroid signaling controls PILS-dependent nuclear auxin input in Arabidopsis thaliana

Auxin and brassinosteroids (BR) are crucial growth regulators and display overlapping functions during plant development. Here, we reveal an alternative phytohormone crosstalk mechanism, revealing that brassinosteroid signaling controls nuclear abundance of auxin. We performed a forward genetic screen for imperial pils (imp) mutants that enhance the overexpression phenotypes of PIN-LIKES (PILS) putative intracellular auxin transport facilitator. Here we report that the imp1 mutant is defective in the brassinosteroid-receptor BRI1. Our data reveals that BR signaling transcriptionally and posttranslationally represses accumulation of PILS proteins at the endoplasmic reticulum, thereby increasing nuclear abundance and signaling of auxin. We demonstrate that this alternative phytohormonal crosstalk mechanism integrates BR signaling into auxin-dependent organ growth rates and likely has widespread importance for plant development.

plant biology↗

bioRxiv2019

Cytokinin functions as an asymmetric and anti-gravitropic signal in lateral roots

Directional organ growth allows the plant root system to strategically cover its surroundings. Intercellular auxin transport is aligned with the gravity vector in the primary root tips, facilitating downward organ bending at the lower root flank. Here we show that cytokinin signaling functions as a lateral root specific anti-gravitropic component, promoting the radial distribution of the root system. We performed a genome-wide association study and revealed that signal peptide processing of Cytokinin Oxidase 2 (CKX2) affects its enzymatic activity and, thereby, determines the degradation of cytokinins in natural Arabidopsis thaliana accessions. Cytokinin signaling interferes with growth at the upper lateral root flank and thereby prevents downward bending. Our interdisciplinary approach revealed that two phytohormonal cues at opposite organ flanks counterbalance each others negative impact on growth, suppressing organ growth towards gravity and allow for radial expansion of the root system.

plant biology↗

bioRxiv2018

PIN7 auxin carrier is a terminator of radial root expansion in Arabidopsis thaliana

Directional growth of lateral roots is critical for radial expansion and soil coverage. Despite its importance, almost nothing is known about its molecular determinants. Initially, young lateral roots (LRs) grow away from the parental root maintaining the angle acquired shortly after emergence. A second downwards bending response to gravity terminates the so-called plateau phase and thereby limits the radial root expansion. Here we show that the exit from the plateau phase correlates with an increase in auxin signalling at the tip of LRs. Moreover, the increase in auxin levels induces the termination of the plateau phase, which requires PIN auxin efflux carriers. Our data suggests that the developmental increase of auxin triggers the preferential de-repression of PIN7 in gravity-sensing columella cells. The subsequent polarization of PIN7 heralds the bending towards gravity and, hence, the exit from the plateau phase. This developmental framework reveals the distinct roles of PIN auxin efflux carriers in controlling the radial growth of root systems.

plant biology↗

bioRxiv2018

PILS6 is a temperature-sensitive regulator of nuclear auxin input and organ growth in Arabidopsis thaliana

Global warming is threatening plant productivity, because plant growth is highly sensitive to elevated temperatures. High temperature (HT) triggers the auxin biosynthesis-dependent growth in aerial tissues. On the other hand, the contribution of auxin to HT-induced root growth is currently under debate. Here we show that the putative intracellular auxin carrier PIN-LIKES 6 (PILS6) is a negative regulator of organ growth and that its abundance is highly sensitive to HT. PILS6 localises to the endoplasmic reticulum (ER) and limits the nuclear availability of auxin, consequently reducing the auxin signalling output. HT represses the transcription and protein abundance of PILS6 specifically in the root tip, which impacts on PILS6-dependent root organ growth rates. Accordingly, we hypothesize that PILS6 is part of a novel mechanism, linking HT to auxin responses in roots.

plant biology↗

bioRxiv2017

LRX- and FER-dependent extracellular sensing coordinates vacuolar size for cytosol homeostasis

Cellular elongation requires the defined coordination of intra- and extracellular processes. The vacuole is the biggest plant organelle and its dimension has a role in limiting cell expansion (Lofke et al., 2015; Scheuring et al., 2016). We reveal that the increase in vacuolar occupancy enables cellular elongation with relatively little enlargement of the cytosole. It remains, however, completely unknown how the vacuolar size is coordinated with other growth-relevant processes. Intriguingly, we show that extracellular constraints impact on the intracellular expansion of the vacuole. The underlying cell wall sensing mechanism requires the interaction of the extracellular leucine-rich repeat extensin (LRX) with the receptor-like kinase Feronia (FER). Our data suggests that LRX links the plasma membrane localised FER with the cell wall, allowing this module to jointly sense and convey extracellular signals to the underlying cell. This mechanism coordinates cell wall acidification/loosening with the increase in vacuolar size, contributing cytosol homeostasis during plant cell expansion.

plant biology↗