Biology subjects

Maizel, A.

Publications and source records attributed to Maizel, A..

15 recordsLinked to original sources

bioRxiv2025

Mechanics and growth coordination define SOSEKI-based polarity fields

The formation of organs requires the coordinated growth of cells and tissues relative to the main body axes. Plant growth is typically anisotropic and mechanically coupled through contiguous cell walls, yet how these physical patterns link to cell and tissue polarity remains unclear. Here, we use SOSEKI (SOK) proteins--previously thought to report global polarity fields--as markers to dissect how polarity arises during lateral root (LR) organogenesis. Live imaging revealed that SOK polarisation does not follow a uniform global field but instead responds to local differences in growth and mechanical state between neighbouring tissues. SOKs accumulate at interfaces separating domains of distinct growth behaviour and dissipate under compressive stress. After perturbing tissue interfaces or the mechanical continuity of the tissue, the coherence of the polarity was disrupted, indicating that stable axis establishment requires mechanical coupling across the cell wall network. Our results suggest that SOK polarisation is mechanoresponsive, linking tissue mechanics to polarity and axis establishment.

plant biology↗

bioRxiv2025

Spatiotemporal Dynamics of Anionic Phospholipids Orchestrate Lateral Root Initiation and Morphogenesis in Arabidopsis thaliana

Lateral root (LR) development in Arabidopsis thaliana requires precise coordination of pericycle founder cell (FC) specification, patterning, and morphogenesis. While auxin signalling is well established in this process, the role of membrane lipid signalling--particularly phosphoinositides--remains less understood. Here, we investigate the contribution of the anionic phospholipids PI4P, PI(4,5)P2, and phosphatidylserine (PS) to LR formation using live-cell biosensors, genetic mutants, and inducible lipid depletion tools. We show that PI4P is uniformly distributed throughout lateral root primordia (LRPs), whereas PI(4,5)P2 is specifically depleted in the proliferative core during early LRP development. Time-lapse imaging revealed stable PI4P and PI(4,5)P2 levels before and after FC activation, while PS increased rapidly post-activation. In xylem-pole pericycle (XPP) cells, PI(4,5)P2 decreased and PS increased following LR initiation, with both changes occurring in a membrane-domain-specific manner. Genetic analysis of the pip5k1pip5k2 double mutant, deficient in PI(4,5)P2 synthesis, revealed impaired LR initiation and emergence. Conversely, inducible depletion of PI(4,5)P2 using the iDePP system enhanced LRP initiation and accelerated development when activated after FC specification. These results suggest that PI4P functions as a stable basal lipid, while PI(4,5)P2 and PS undergo dynamic, spatially regulated changes critical for LR progression. Notably, PI(4,5)P2 acts as a negative regulator of LRP initiation and morphogenesis. Our findings highlight how lipid signalling, in coordination with hormonal cues, provides spatial and temporal control over pericycle cell behaviour and lateral root organogenesis. SIGNIFICANCE STATEMENTThis study reveals how specific membrane lipids help control where and when new lateral roots form in plants. While plant hormones like auxin are known to guide root branching, this work shows that lipids such as PI(4,5)P2 and phosphatidylserine also play key roles. Using live imaging and genetic tools, we found that reducing PI(4,5)P2 in certain root cells promotes root growth by triggering cell division and development. In contrast, phosphatidylserine level increases right when root-forming cells become active. These discoveries highlight a new layer of control in plant development and suggest that lipids help fine-tune the formation of roots, which is essential for how plants take up water and nutrients.

plant biology↗

bioRxiv2023

Mechanotransduction in Lateral Root Initiation: A Model Integrating Growth Mechanics and Auxin Signaling

Plant development relies on the precise coordination of cell growth, which is influenced by the mechanical constraints imposed by rigid cell walls. The hormone auxin plays a crucial role in regulating this growth by altering the mechanical properties of cell walls. During the post-embryonic formation of lateral roots, pericycle cells deep within the main root are triggered by auxin to resume growth and divide to form a new root. This growth involves a complex interplay between auxin, growth, and the resolution of mechanical conflicts with the overlying endodermis. However, the exact mechanisms by which this coordination is achieved are still unknown. Here, we propose a model that integrates tissue mechanics and auxin transport, revealing a connection between the auxin-induced relaxation of mechanical stress in the pericycle and auxin signalling in the endodermis. We show that the endodermis initially limits the growth of pericycle cells, resulting in a modest initial expansion. However, the associated stress relaxation is sufficient to redirect auxin to the overlying endodermis, which then actively accommodates the growth, allowing for the subsequent development of the lateral root. Our model uncovers that increased pericycle turgor and decreased endodermal resistance licence expansion of the pericycle and how the topology of the endodermis influences the formation of the new root. These findings highlight the interconnected relationship between mechanics and auxin flow during lateral root initiation, emphasizing the vital role of the endodermis in shaping root development through mechanotransduction and auxin signalling.

plant biology↗

bioRxiv2023

GreenGate 2.0: backwards compatible addons for assembly of complex transcriptional units and their stacking with GreenGate

Molecular cloning is a crucial technique in genetic engineering that enables the precise design of synthetic transcriptional units (TUs) and the manipulation of genomes. GreenGate and several other modular molecular cloning systems were developed about ten years ago and are widely used in plant research. All these systems define grammars for assembling transcriptional units from building blocks, cloned as Level 0 modules flanked by four-base pair overhangs and recognition sites for a particular Type IIs endonuclease. Modules are efficiently assembled into Level 1 TUs in a hierarchical assembly process, and Level 2 multigene constructs are assembled by stacking Level 1 TUs. GreenGate is highly popular but has three main limitations. First, using ad-hoc overhangs added by PCR and classical restriction/ligation prevents the efficient use of a one-pot, one-step reaction to generate entry clones and domesticate internal sites; second, a Level 1 TU is assembled from a maximum of six modules, which may be limiting for applications such as multiplex genome editing; third, the generation of Level 2 assemblies is sequential and inefficient. GreenGate 2.0 (GG2.0) expands GreenGate features. It introduces additional overhangs, allowing for the combination of up to 12 Level 0 modules in a Level 1 TU. It includes a Universal Entry Generator plasmid (pUEG) to streamline the generation of Level 0 modules. GG2.0 introduces GreenBraid, a convenient method for stacking transcriptional units iteratively for multigene assemblies. Importantly, GG2.0 is backwards compatible with most existing GreenGate modules. Additionally, GG2.0 includes Level 0 modules for multiplex expression of guide RNAs for CRISPR/Cas9 genome editing and pre-assembled Level 1 vectors for dexamethasone-inducible gene expression and ubiquitous expression of plasma membrane and nuclear fluorescent markers. GG2.0 streamlines and increases the versatility of assembling complex transcriptional units and their combination.

plant biology↗

bioRxiv2022

TOR acts as metabolic gatekeeper for auxin-dependent lateral root initiation in Arabidopsis thaliana

Plants post-embryonic organogenesis requires matching the available metabolic resources to the developmental programs. The root system is determined by the formation of lateral roots (LR), which in Arabidopsis thaliana entails the auxin-induced activation of founder cells located in the pericycle. While the allocation of sugars to roots influences root branching, how sugar availability is sensed for auxin-triggered formation of LRs remains unknown. Here, we combine metabolic profiling with cell-specific genetic interference to show that LR formation is an important sink for carbohydrate accompanied by a switch to glycolysis. We show that the target-of-rapamycin (TOR) kinase is locally activated in the pericycle and the founder cells and that both chemical and genetic inhibition of TOR kinase lead to a block of LR initiation. TOR marginally affects the auxin-induced transcriptional response of the pericycle but modulates the translation of ARF19, ARF7 and LBD16, three key targets of auxin signalling. These data place TOR as a gatekeeper for post-embryonic LR formation that integrates local auxin-dependent pathways with systemic metabolic signals, modulating the translation of auxin induced gene expression.

plant biology↗

bioRxiv2022

Paf1C denoises transcription and growth patterns to achieve organ shape reproducibility

In multicellular systems, all cells exhibit transcriptional noise. However, its exact contribution to morphogenesis often remains unclear, especially in animals where cells can also move. Here we take advantage of walled plant cells, where transcriptional noise happens in tissues with a fixed topology. Using synchronously growing guard cells in stomata, we demonstrate that mutation in VIP3, a subunit of the conserved polymerase-associated factor 1 complex (Paf1C), increases transcriptional noise in Arabidopsis. This conclusion could be generalized to other group of cells at the shoot apex. Such noise translates into growth and shape defects. Indeed, in vip3 sepals, we measured higher growth heterogeneity between adjacent cells, with molecular evidence of increased local mechanical conflicts. This even culminated with the presence of negatively growing cells in specific growth conditions. Interestingly, such increased local noise makes the regional pattern of growth less clear-cut. Reduced regional conflicts lead to delay in organ growth arrest, ultimately making final organ shapes and sizes more variable. We propose that transcriptional noise is managed by Paf1C to ensure organ robustness by building up mechanical conflicts at the regional scale, instead of the local scale. HIGHLIGHTSO_LIPaf1C controls transcriptional noise in Arabidopsis C_LIO_LIPaf1C reduces growth heterogeneity and dampens local mechanical conflicts C_LIO_LIImpairing both Paf1C and microtubules can trigger negative growth in Arabidopsis C_LIO_LIScaling up local conflicts to regional ones with sharp boundaries contributes to organ shape robustness C_LI

developmental biology↗

bioRxiv2022

Progressive maturation of the root apical meristem in Arabidopsis thaliana lateral roots

Meristems are stem cells niches that support the formation of all plant organs and are either set during embryogenesis and maintained throughout the plant life or specified de novo, post-embryonically. The embryo-derived root apical meristem is organized around a group of infrequently dividing cells, the quiescent centre, that maintains the stem cells, organizes growth along two axes and owing to its resistance to 3ic stress can replace damaged stem cells. In most cases, lateral roots post-embryonically branch off the primary and establish a new root meristem which organization is identical to the primary root one. The cellular and molecular processes underpinning the emergence of new stem cell niches are not well known. Here, we characterize the de novo establishment of the root apical meristem in lateral roots. While the position of the new stem cell niche is set early during morphogenesis, its cellular layout, unique gene expression profile and mitotic quiescence are only acquired after emergence concomitant to the establishment of two diverging growth axis. Our results show that the intertwined attributes of the mature root stem cell niche are progressively acquired during lateral root formation, and support a model in which the position of the stem cell niche emerges from the establishment of diverging growth axis. HighlightAnalyze of the ontogeny of the quiescent center during lateral root ontogeny reveal its late formation and supports that its emergence results from the establishment of two diverging growth axis.

plant biology↗

bioRxiv2021

Microtubule-based perception of mechanical conflicts controls plant organ morphogenesis

Precise coordination between cells and tissues is essential for differential growth in plants. During lateral root formation in Arabidopsis thaliana, the endodermis is actively remodeled to allow outgrowth of the new organ. Here, we show that microtubule arrays facing lateral root founder cells display a higher order compared to arrays on the opposite wall of the same cell, and this asymmetry is required for endodermal remodeling and lateral root initiation. We identify that MICROTUBULE ASSOCIATED PROTEIN 70-5 is necessary for the establishment of this spatially defined microtubule organization and endodermis remodeling, and thus contributes to lateral root morphogenesis. We propose that MAP70-5 and cortical microtubule arrays in the endodermis integrate the mechanical signals generated by lateral root outgrowth, facilitating the channeling of organogenesis.

plant biology↗

bioRxiv2020

Integration of Cell Growth and Asymmetric Division During Lateral Root Initiation In Arabidopsis thaliana

Lateral root formation determines to a large extent the ability of plants to forage their environment and thus their growth. In Arabidopsis thaliana and other angiosperms, lateral root initiation requires radial cell expansion and several rounds of anticlinal cell divisions that give rise to a central core of small pericycle cells, which express different markers than the larger surrounding cells. These small central cells then switch their plane of divisions to periclinal, and give rise to seemingly morphologically similar daughter cells that have different identities and establish the different cell types of the new root. Although the execution of these two types of divisions is tightly regulated and essential for the correct development of the lateral root, we know little about their geometrical features. Here we analyse a four-dimensional reconstruction of the first stages of lateral root formation and analyze the geometric features of the anticlinal and periclinal divisions. We identify that the periclinal divisions of the small central cells are morphologically dissimilar and asymmetric. We show that mother cell volume is different when looking at anticlinal versus periclinal divisions and the repeated anticlinal divisions do not lead to reduction in cell volume although cells are shorter. Finally, we show that cells undergoing a periclinal division are characterized by a strong cell expansion. Our results indicate that cells integrate growth and division to precisely partition their volume upon division during the first two stages of lateral root formation.

plant biology↗

bioRxiv2020

Accurate And Versatile 3D Segmentation Of Plant Tissues At Cellular Resolution

Quantitative analysis of plant and animal morphogenesis requires accurate segmentation of individual cells in volumetric images of growing organs. In the last years, deep learning has provided robust automated algorithms that approach human performance, with applications to bio-image analysis now starting to emerge. Here, we present PlantSeg, a pipeline for volumetric segmentation of plant tissues into cells. PlantSeg employs a convolutional neural network to predict cell boundaries and graph partitioning to segment cells based on the neural network predictions. PlantSeg was trained on fixed and live plant organs imaged with confocal and light sheet microscopes. PlantSeg delivers accurate results and generalizes well across different tissues, scales, and acquisition settings. We present results of PlantSeg applications in diverse developmental contexts. PlantSeg is free and open-source, with both a command line and a user-friendly graphical interface.

plant biology↗

bioRxiv2019

Tissue-wide integration of mechanical cues promotes efficient auxin patterning

New plants organs form by local accumulation of auxin, which is transported by PIN proteins that localize following mechanical stresses. As auxin itself modifies tissue mechanics, a feedback loop between tissue mechanics and auxin patterning unfolds - yet the impact of tissue-wide mechanical coupling on auxin pattern emergence remains unclear. Here, we use a hybrid model composed of a vertex model for plant tissue mechanics, and a compartment model for auxin transport to explore the collective mechanical response of the tissue to auxin patterns and how it feeds back onto auxin transport. We compare a model accounting for a tissue-wide mechanical integration to a model where mechanical stresses are averaged out across the tissue. We show that only tissue-wide mechanical coupling leads to focused auxin spots, which we show to result from the formation of a circumferential stress field around these spots, self-reinforcing PIN polarity and auxin accumulation.

plant biology↗

bioRxiv2019

PLETHORA and WOX5 interaction and subnuclear localisation regulates Arabidopsis root stem cell maintenance

Maintenance and homeostasis of the stem cell niche (SCN) in the Arabidopsis root is essential for growth and development of all root cell types. The SCN is organized around a quiescent center (QC) maintaining the stemness of cells in direct contact. The key transcription factors (TFs) WUSCHEL-RELATED HOMEOBOX 5 (WOX5) and PLETHORAs (PLTs) are expressed in the SCN where they maintain the QC and regulate distal columella stem cell (CSC) fate. Here, we describe the concerted mutual regulation of the key TFs WOX5 and PLTs on a transcriptional and protein interaction level. Additionally, by applying a novel SCN staining method, we demonstrate that both WOX5 and PLTs regulate root SCN homeostasis as they control QC quiescence and CSC fate interdependently. Moreover, we uncover that some PLTs, especially PLT3, contain intrinsically disordered prion-like domains (PrDs) that are necessary for complex formation with WOX5 and its recruitment to subnuclear microdomains/nuclear bodies (NBs) in the CSCs. We propose that this partitioning of PLT-WOX5 complexes to NBs, possibly by phase separation, is important for CSC fate determination.

plant biology↗

bioRxiv2019

Cytoskeleton dynamics control early events of lateral root initiation in Arabidopsis

How plant cells re-establish differential growth to initiate organs is poorly understood. Morphogenesis of lateral roots relies on the tightly controlled radial expansion and asymmetric division of founder cells. The cellular mechanisms that license and ensure these features are unknown. Here, we quantitatively analyse F-actin and microtubule dynamics during LR initiation. Using mutants, pharmacological and tissue-specific genetic perturbations, we show that dynamic reorganisation of both microtubule and F-actin networks is required for the asymmetric expansion of the founder cells. This cytoskeleton remodelling intertwine with auxin signalling in the pericycle and endodermis in order for founder cells to acquire a basic polarity required for initiating LR development. Our results reveal the conservation of cell remodelling and polarisation strategies between the Arabidopsis zygote and lateral root founder cells. We propose that coordinated, auxin-driven reorganisation of the cytoskeleton licenses asymmetric cell growth and divisions during embryonic and post-embryonic organogenesis. HIGHLIGHTSO_LIFailure for lateral root founder cells to undergo asymmetric radial expansion before division, leads to aberrant organ formation. C_LIO_LICortical microtubules arrays reorganise to facilitate this asymmetric expansion and F-actin the asymmetric division. C_LIO_LICytoskeletal reorganisation depends on auxin signalling. C_LIO_LINew genetic tools allow to perturb microtubules or actin in an inducible and cell-type specific manner. C_LI

plant biology↗

bioRxiv2018

ARF5/MONOPTEROS directly regulates miR390 expression in theArabidopsis thaliana primary root meristem

The root meristem is organized around a quiescent centre surrounded by stem cells that generate all cell types of the root. In the transit amplifying compartment progeny of stem cells further divide prior to differentiation. Auxin controls the size of this transit-amplifying compartment via Auxin Response Factors (ARF) that interact with Auxin Response Elements (AuxRE) in the promoter of their targets. The microRNA miR390 regulates abundance of ARF2, ARF3 and ARF4 by triggering the production of trans-acting (ta)-siRNA from TAS3. This miR390/TAS3/ARF regulatory module confers sensitivity and robustness to auxin responses in diverse developmental contexts. Here, we show that miR390 is expressed in the transit-amplifying compartment of the root meristem where it modulates response to auxin. A single AuxRE bound by ARF5/MONOPTEROS (MP) in miR390 promoter is necessary for miR390 expression in this compartment. We show that interfering with ARF5/MP dependent auxin signaling attenuates miR390 expression in the transit-amplifying compartment. Our results show that ARF5/MP regulates directly the expression of miR390 in the basal root meristem. We propose that ARF5, miR390 and the ta-siRNAs-regulated ARFs are necessary to maintain the size of the transit-amplifying region of the meristem.\n\nOne sentence summaryThe expression of miR390 in the Arabidopsis basal root meristem is controlled by ARF5/MONOPTEROS.

plant biology↗

bioRxiv2018

Cell death in cells overlying lateral root primordia contributes to organ growth in Arabidopsis

Unlike animal development, plant organ growth is widely accepted to be determined by cell division without any contribution of cell elimination. We investigated this paradigm during Arabidopsis lateral root formation when growth of the new primordia (LRP) from pericycle-derived stem cells deep inside the root is reportedly facilitated by remodeling of the walls of overlying cells without apparent cell death. However, we observed the induction of marker genes for cell types undergoing developmental cell death in several cells overlying the growing LRP. Transmission electron microscopy, time-lapse confocal and light sheet microscopy techniques were used to establish that cell death occurred at least in a subset of endodermal LRP-overlying cells during organ emergence. Significantly, organ emergence was retarded in mutants lacking a positive cell death regulator, and restored by inducing cell death in cells overlying LRP. Hence, we conclude that in the case of LRP, cell elimination contributes to organ growth.

plant biology↗