Biology subjects

Fendrych, M.

Publications and source records attributed to Fendrych, M..

18 recordsLinked to original sources

bioRxiv2026

Hormone-dependent receptor docking controls calcium channel activity in plants

The phytohormone auxin is a central coordinator of plant growth and development. Besides its canonical effect on gene transcription1,2, auxin triggers an ultra-rapid calcium ion influx that initiates the root gravitropic response3. The nature of the so-called rapid auxin pathway connecting the AFB1 auxin receptor3,4 and plasma membrane calcium channels remained unknown. Here, we show that auxin induces the direct interaction of the AFB1 receptor with the CNGC14 calcium channel. As the AFB1 receptor is independent of the ubiquitin ligase complex5, the auxin-induced interaction translates into relocalization of the receptor to the plasma membrane. We identify the interaction interface and provide evidence that the docking of the receptor to the channel complex activates Ca2+ influx and triggers growth inhibition. These findings position a calcium channel as an unprecedented component of the AFB1 auxin receptor complex. The ligand-dependent localization shift of a TIR1/AFB family receptor represents a novel paradigm in signal transduction and opens the possibility of unforeseen branches of auxin signaling pathways.

plant biology↗

bioRxiv2026

Cell wall charge gates iron availability in plant roots

Plants acquire essential mineral nutrients from the soil, yet these elements must first traverse the extracellular matrix of the root before reaching the cell surface. How the physical properties of this extracellular compartment influence nutrient distribution and availability remains poorly understood. In plants, this extracellular matrix is formed by the cell wall, which carries a dynamically regulated negative charge that can change during development and in response to environmental cues. Here we demonstrate that cell wall charge functions as a tunable electrostatic gate that determines how iron is partitioned between retention and bioavailability. This decoupling between iron abundance and availability reveals a fundamental tradeoff imposed by extracellular electrostatics. A mechanistic diffusion-binding model shows that increasing wall charge inherently enhances iron sequestration while limiting its mobility at the cell surface. Genetic perturbation of pectin de-methylesterification validates this principle in vivo. Moreover, iron limitation itself triggers active remodeling of cell wall charge, dynamically shifting the balance toward increased iron accessibility. Together, these findings identify the plant cell wall as an active regulator of nutrient homeostasis rather than a passive barrier. By dynamically modulating extracellular electrostatics, roots control iron partitioning and bioavailability, uncovering a new physical layer of regulation in plant mineral nutrition. One-Sentence SummaryThe plant cell wall operates as a tunable electrostatic gate that buffers and releases iron through spatially and environmentally regulated charge dynamics.

plant biology↗

bioRxiv2025

POLYGALACTURONASES REGULATED BY AUXIN facilitate root cell elongation in Arabidopsis thaliana via pectin remodeling

Root cell elongation, the main driver of root growth, is tightly associated with cell wall remodeling, particularly through pectin modifications, which facilitate cell wall loosening and strengthening while maintaining structural integrity. Root cell elongation is precisely regulated by the phytohormone auxin, which has long been known to inhibit this process. The molecular pathways through which auxin influences cell wall modifications remain poorly understood. In this study, we explore the transcriptional regulation of cell wall-related genes by auxin in Arabidopsis thaliana roots. The nuclear auxin pathway altered the expression of numerous cell-wall related genes, suggesting dynamic modification of the cell wall during root cell elongation. We identified novel root-specific polygalacturonases (PGs), enzymes involved in pectin degradation, which we termed POLYGALACTURONASES REGULATED BY AUXIN (PGRAs). PGRAs are expressed specifically in the root epidermis, beginning at the elongation zone. Our results demonstrate that induction of PGRA1 expression initially promotes root cell elongation, while long term overexpression inhibits root growth. Auxin downregulates PGRA1 in the elongation zone, and plants lacking PGRAs fail to increase root growth rate in response to reduced auxin levels. This suggests that auxin downregulates PGRA expression to prevent PGRA-mediated pectin remodeling, thereby contributing to inhibition of root cell elongation. We established a novel link between auxin signaling and pectin modifications in the control of cell growth. These findings provide new insights into the molecular mechanisms through which auxin regulates root cell elongation, highlighting the role of pectin matrix modifications in this process.

plant biology↗

bioRxiv2025

Gibberellin-deactivating GA2OX enzymes act as a hub for auxin-gibberellin crosstalk in Arabidopsis thaliana root growth regulation

Plant bodies are built from immobile cells, making the regulation of cell expansion essential for growth, development, and adaptation. In roots, cell elongation executes the movement of the root tips through soil. This process is tightly controlled by numerous signaling pathways. Among these, gibberellin and auxin signaling stand out for their contrasting effects on root growth, interacting through complex crosstalk at multiple regulatory levels. Here we reveal the molecular basis of the auxin-gibberellin crosstalk in the model plant Arabidopsis thaliana. We show that auxin signaling pathway steers the expression of GIBBERELLIN 2-OXIDASES (GA2OX), key gibberellin-deactivating enzymes in the root elongation zone. GA2OX are negative regulators of root cell elongation; GA2OX8 overexpression decreases gibberellin levels and inhibits root cell elongation, in contrast, the ga2ox heptuple mutant roots show elevated gibberellin levels in the elongation zone and grow longer roots. Shoot derived auxin can regulate GA2OX8 expression in roots, linking systemic auxin signaling to local gibberellin modulation. In addition, GA2OX8 is active in vascular tissues and the stem cell niche, tissues with high auxin levels. Loss of GA2OX genes results in altered stem cell niche, including increased quiescent center size and expanded root cell layers, highlighting the role of these enzymes in maintaining tissue organization. Together, our findings identify GA2OX6 and GA2OX8 enzymes as key mediators of auxin-gibberellin crosstalk, providing insights into their roles in root elongation, vascular development, and stem cell niche maintenance. These results expand our understanding of how auxin integrates with gibberellin signaling to coordinate root development and growth dynamics.

plant biology↗

bioRxiv2025

Armadillo Repeat Only Proteins Are Crucial for the Function of Plant CNGC Channels

The versatile Ca2+ signaling system governs plant responses to a wide array of environmental and developmental cues. CYCLIC NUCLEOTIDE-GATED CHANNELS (CNGCs) trigger cellular responses to diverse signals, including phytohormones, biotic and abiotic stresses; and as such their activity is tightly controlled. Unlike their animal paralogs, plant CNGCs does not seem to be gated by cyclic nucleotides, and the mechanism of their activation remains unresolved. Here we report ARMADILLO REPEAT ONLY (ARO) proteins as novel, plant-specific, and essential activators of plant CNGCs. Reciprocal proximity labeling revealed interactions between all sporophytic CNGCs and AROs. Loss-of-function aro mutants fail to induce Ca2+ transients in response to known CNGC-triggering stimuli. Structural modeling, mutational analysis, and electrophysiological data show that AROs assemble into a complex with CNGC tetramers by interaction with the conserved Calmodulin-binding IQ domain. AROs represent CNGC activators, competing with Calmodulins, showcasing an evolutionarily unique solution to regulation of calcium signaling in plants.

plant biology↗

bioRxiv2024

Programmed cell death and stomatal density regulate anther opening in response to ambient humidity

Anther dehiscence is the process that facilitates pollen release from mature anthers in flowering plants. Despite its crucial importance to reproduction, the underlying molecular regulations and the integration of environmental information remain poorly understood. Using controlled humidity treatments of Arabidopsis thaliana flowers, we show here that high humidity prevents anthers from opening. Lower and higher stomatal densities correlate with slower and faster dehiscence dynamics, respectively, suggesting that controlled transpiration regulates anther opening. Furthermore, analyses of subcellular markers revealed that specific anther tissues undergo a spatially controlled programmed cell death (PCD) process as anthers open. Notably, genetic inhibition of PCD networks delays, whereas precocious PCD induction promotes, anther dehiscence. Our data shed new light on the interplay between ambient humidity, controlled transpiration, and PCD processes in regulating timely pollen release in the model plant Arabidopsis.

plant biology↗

bioRxiv2023

Chitosan stimulates root hair callose deposition and inhibits root hair growth

Although angiosperm plants have a general capacity to react after the immunity elicitor chitin or chitosan treatment by the cell wall callose deposition, this response in particular cell types and its evolutionary conservation is not understood. Here we show that also the growing root hairs (RHs) of Arabidopsis can respond to a mild (0.001%) chitosan treatment by the callose deposition and by a deceleration of the RH growth. We demonstrate that the glucan synthase-like 5 (GSL5)/PMR4 is vital for chitosan-induced callose deposition but not for RH growth inhibition. Upon the higher chitosan concentration (0.01%) treatment, RHs do not deposit callose, while growth inhibition is prominent. To understand the specificities of the low and high concentration chitosan treatments, we analysed the corresponding PTI signalling components, gene expression, and RH cellular endomembrane and cytoskeleton modifications. Importantly, chitosan-induced callose deposition is also present in the functionally analogous and evolutionarily only distantly related RH-like structures rhizophores (lycophytes) and rhizoids (bryophytes). Our results point to the RH callose deposition as a conserved strategy of soil-anchoring plant cells (rhizoids/rhizophores/RHs) to deal with mild biotic stress. At the same time, high chitosan concentration prominently disturbs intracellular dynamics, tip-localised endomembrane compartments and RH growth, precluding callose deposition.

plant biology↗

bioRxiv2023

Auxin coreceptor IAA17/AXR3 controls cell elongation in Arabidopsis thaliana root by modulation of auxin and gibberellin perception

The nuclear TIR1/AFB - Aux/IAA auxin pathway plays a crucial role in regulating plant growth and development. Specifically, the IAA17/AXR3 protein participates in root development, and the accumulation of its mutant variant, AXR3-1, which cannot bind auxin, leads to severe root growth phenotype and agravitropism. However, the mechanism by which AXR3 regulates cell elongation is not fully understood. Here we show that the inducible expression of AXR3-1 in the Arabidopsis thaliana root triggers excessive cell elongation that is followed by growth arrest of the root. We exploited this effect to reveal the underlying molecular mechanism of AXR3 action. We show that AXR3-1 acts exclusively in the nucleus where it interferes with the nuclear auxin transcriptional pathway, while the rapid cytoplasmic auxin root growth response is not affected. The analysis of the transcriptome of the induced AXR3-1 roots revealed changes in phytohormone perception and homeostasis. We show that the accumulation of AXR3-1 disturbs auxin homeostasis which leads to excessive auxin accumulation. At the same time, the reaction of the AXR3-1 roots to gibberellin is altered. These results show that the IAA17/AXR3 maintains an optimal cell elongation rate by controlling the auxin response, auxin homeostasis and the interplay with gibberellin signaling.

plant biology↗

bioRxiv2023

The AFB1 auxin receptor controls the cytoplasmic auxin response pathway in Arabidopsis thaliana

The phytohormone auxin triggers root growth inhibition within seconds via a non-transcriptional pathway. Among members of the TIR1/AFBs auxin receptor family, AFB1 has a primary role in this rapid response. However, the unique features that confer this specific function have not been identified. Here we show that the N-terminal region of AFB1, including the F-box domain and residues that contribute to auxin binding, are essential and sufficient for its specific role in the rapid response. Substitution of the N-terminal region of AFB1 with that of TIR1 disrupts its distinct cytoplasm-enriched localization and activity in rapid root growth inhibition. Importantly, the N-terminal region of AFB1 is indispensable for auxin-triggered calcium influx which is a prerequisite for rapid root growth inhibition. Furthermore, AFB1 negatively regulates lateral root formation and transcription of auxin-induced genes, suggesting that it plays an inhibitory role in canonical auxin signaling. These results suggest that AFB1 may buffer the transcriptional auxin response while it regulates rapid changes in cell growth that contribute to root gravitropism.

plant biology↗

bioRxiv2022

An ultra-fast, proteome-wide response to the plant hormone auxin

The plant signaling molecule auxin controls growth and development through a simple nuclear pathway that regulates gene expresion. There are however several cellular and physiological responses to auxin that occur within seconds, far too rapid to be mediated by transcriptional changes, for which no molecular mechanism has yet been identified. Using a phosphoproteomic strategy in Arabidopsis thaliana roots, we identify an ultra-rapid auxin response system that targets over 1700 proteins, many within 30 seconds. Auxin response is chemically specific, requires known auxin-binding proteins, and targets various pathways. Through exploring its temporal dynamics, we infer auxin-triggered kinase-substrate networks and identify apoplastic pH changes as a target of signaling and as part of a relay mechanism. By generating a variety of phosphoproteomic datasets, integrated with structural information in a web-app, and by demonstrating analysis and inference strategies, we offer a resource to explore rapid and dynamic signaling in plants.

plant biology↗

bioRxiv2022

A RAF-like kinase mediates a deeply conserved, ultra-rapid auxin response

The plant signaling molecule auxin triggers both fast and slow cellular responses across the plant kingdom, including both land plants and algae. A nuclear response pathway mediates auxin-dependent gene expression, and controls a range of growth and developmental processes in land plants. It is unknown what mechanisms underlie both the physiological responses occurring within seconds, and the responses in algae, that lack the nuclear auxin response pathway. We discovered an ultra-fast proteome-wide phosphorylation response to auxin across 5 land plant and algal species, converging on a core group of shared target proteins. We find conserved rapid physiological responses to auxin in the same species and identified a RAF-like protein kinase as a central mediator of auxin-triggered phosphorylation across species. Genetic analysis allowed to connect this kinase to both auxin-triggered protein phosphorylation and a rapid cellular response, thus identifying an ancient mechanism for fast auxin responses in the green lineage.

plant biology↗

bioRxiv2022

The AUX1-AFB1-CNGC14 module establishes longitudinal root surface pH profile

Plant roots navigate in the soil environments following the gravity vector. Cell divisions in the meristem and rapid cell growth in the elongation zone propel the root tips through the soil. Actively elongating cells acidify their apoplast to enable cell wall extension by the activity of plasma membrane AHA H+-ATPases. The phytohormone auxin, central regulator of gravitropic response and root development, inhibits root cell growth, likely by rising the pH of the apoplast. However, the role of auxin in the regulation of the apoplastic pH gradient along the root tip is unclear. Here we show, by using an improved method for visualization and quantification of root surface pH, that the Arabidopsis thaliana root surface pH shows distinct acidic and alkaline zones, which are not primarily determined by the activity of AHA H+-ATPases. Instead, the distinct domain of alkaline pH in the root transition zone is controlled by a rapid auxin response module, consisting of the AUX1 auxin influx carrier, the AFB1 auxin co-receptor and the CNCG14 calcium channel. We demonstrate that the rapid auxin response pathway is required for an efficient navigation of the root tip.

plant biology↗

bioRxiv2022

Spatial and Temporal Regulation of Parent-of-Origin Allelic Expression in the Endosperm

Genomic imprinting promotes differential expression of parental alleles in the endosperm of flowering plants, and is regulated by epigenetic modification such as DNA methylation and histone tail modifications in chromatin. After fertilization, the endosperm develops through a syncytial stage before it cellularizes and becomes a nutrient source for the growing embryo. Both in early and late endosperm development regional compartmentalization has been shown, and different transcriptional domains suggest divergent spatial and temporal regional functions. The analysis of the role of parent-of-origin allelic expression in the endosperm as a whole and also investigation of domain specific functions has been hampered by the availability of the tissue for high-throughput transcriptome analyses and contamination from surrounding tissue. Here we have used Fluorescence-Activated Nuclear Sorting (FANS) of nuclear targeted eGFP fluorescent genetic markers to capture parental specific allelic expression from different developmental stages and specific endosperm domains. This RNASeq approach allows us to successfully identify differential genomic imprinting with temporal and spatial resolution. In a systematic approach we report temporal regulation of imprinted genes in the endosperm as well as region specific imprinting in endosperm domains. Our data identifies loci that are spatially differentially imprinted in one domain of the endosperm while biparentally expressed in other domains. This suggests that regulation of genomic imprinting is dynamic and challenges the canonical mechanisms for genomic imprinting.

genetics↗

bioRxiv2021

A sensitive and specific genetically encodable biosensor for potassium ions

Potassium ions (K+) play a critical role as an essential electrolyte in all biological systems. Here we report the crystal structure-guided optimization and directed evolution of an improved genetically encoded fluorescent K+ biosensor, GINKO2. GINKO2 is highly sensitive and specific for K+ and enables in vivo detection of K+ dynamics in multiple species.

bioengineering↗

bioRxiv2021

ACORBA: Automated workflow to measure Arabidopsis thaliana root tip angle dynamic

Plants respond to the surrounding environment in countless ways. One of these responses is their ability to sense and orient their root growth toward the gravity vector. Root gravitropism is studied in many laboratories as a hallmark of auxin-related phenotypes. However, manual analysis of images and microscopy data is known to be subjected to human bias. This is particularly the case for manual measurements of root bending as the selection lines to calculate the angle are set subjectively. Therefore, it is essential to develop and use automated or semi-automated image analysis to produce reproducible and unbiased data. Moreover, the increasing usage of vertical-stage microscopy in plant root biology yields gravitropic experiments with an unprecedented spatiotemporal resolution. To this day, there is no available solution to measure root bending angle over time for vertical-stage microscopy. To address these problems, we developed ACORBA (Automatic Calculation Of Root Bending Angles), a fully automated software to measure root bending angle over time from vertical-stage microscope and flatbed scanner images. Moreover, the software can be used semi-automated for camera, mobile phone or stereomicroscope images. ACORBA represents a flexible approach based on both traditional image processing and deep machine learning segmentation to measure root angle progression over time. By its automated nature, the workflow is limiting human interactions and has high reproducibility. ACORBA will support the plant biologist community by reducing time and labor and by producing quality results from various kinds of inputs. Significance statementACORBA is implementing an automated and semi-automated workflow to quantify root bending and waving angles from images acquired with a microscope, a scanner, a stereomicroscope or a camera. It will support the plant biology community by reducing time and labor and by producing trustworthy and reproducible quantitative data.

plant biology↗

bioRxiv2021

The AFB1 auxin receptor controls rapid auxin signaling and root growth through membrane depolarization in Arabidopsis thaliana

The existence of an electric gradient across membranes is essential for a cell operation. In plants, application of the growth regulator auxin (IAA) causes almost instantaneous membrane depolarization in various cell types, making membrane depolarization a hallmark of the rapid non-transcriptional responses to IAA. Auxin triggers rapid root growth inhibition; a process that underlies gravitropic bending. The growth and depolarization responses to auxin show remarkable similarities in dynamics, requirement of auxin influx and the involvement of the TIR1/AFB auxin coreceptors, but whether auxin-induced depolarization participates in root growth inhibition remains unanswered. Here, we established a toolbox to dynamically visualize membrane potential in vivo in Arabidopsis thaliana roots by combining the DISBAC2(3) fluorescent probe with microfluidics and vertical stage microscopy. This way we show that auxin-induced membrane depolarization tightly correlates with rapid root growth inhibition and that the cells of the transition zone/early elongation zone are the most responsive to auxin. Further, we demonstrate that auxin cycling in and out of the cells through AUX1 influx and PIN2 efflux is not essential for membrane depolarization and rapid root growth inhibition but acts as a facilitator of these responses. The rapid membrane depolarization by auxin instead strictly depends on the AFB1 auxin receptor, while the other TIR1/AFB paralogues contribute to this response. The lack of membrane depolarization in the afb1 mutant explains the lack of the immediate root growth inhibition. Finally, we show that AFB1 is required for the rapid depolarization and rapid growth inhibition of cells at the lower side of the gravistimulated root. These results are instrumental in understanding the physiological significance of membrane depolarization for the gravitropic response of the root and clarify the role of AFB1 as the receptor central for rapid auxin responses, adding another piece to the puzzle in understanding the biology of the phytohormone auxin.

plant biology↗

bioRxiv2020

Local brassinosteroid biosynthesis enables optimal root growth

Brassinosteroid hormones are indispensable for root growth and they control both cell division and cell elongation through the establishment of an increasing signaling gradient along the longitudinal root axis. Because of their limited mobility, the importance of brassinosteroid distribution for achieving the signaling maximum is largely overlooked. Expression pattern analysis of all known brassinosteroid biosynthetic enzymes revealed that not all cells in the Arabidopsis thaliana root possess full biosynthetic machinery and completion of biosynthesis relies on cell-to-cell movement of the hormone precursors. We demonstrate that brassinosteroid biosynthesis is largely restricted to the root elongation zone where it overlaps with brassinosteroid signaling maxima. Moreover, optimal root growth requires hormone concentrations, low in the meristem and high in the root elongation zone attributable to an increased biosynthesis. Our finding that spatiotemporal regulation of hormone synthesis results in a local hormone accumulation provides a paradigm for hormone-driven organ growth in the absence of long-distance hormone transport in plants.

plant biology↗

bioRxiv2017

Live Tracking Of Moving Samples In Confocal Microscopy For Vertically Grown Plant Roots

Roots navigate through soil integrating environmental signals to orient their growth. The Arabidopsis root is a widely used model for developmental, physiological and cell biological studies. Live imaging greatly aids these efforts, but the horizontal sample position and continuous root tip displacement present significant difficulties. Here, we develop a confocal microscope setup for vertical sample mounting and integrated directional illumination. We present TipTracker - a custom software for automatic tracking of diverse moving objects usable on various microscope setups. Combined, this enables observation of root tips growing along the natural gravity vector over prolonged periods of time, as well as the ability to induce rapid gravity or light stimulation. We also track migrating cells in the developing zebrafish embryo, demonstrating the utility of this system in the acquisition of high resolution data sets of dynamic samples. We provide detailed descriptions of the tools enabling the easy implementation on other microscopes.

plant biology↗