Olivier Hamant

Olivier Hamant
French National Institute for Agriculture, Food, and Environment (INRAE) | INRAE · RDP ENS Lyon

About

171
Publications
28,172
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7,339
Citations
Citations since 2016
112 Research Items
5257 Citations
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201620172018201920202021202202004006008001,000
201620172018201920202021202202004006008001,000
Introduction
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Publications

Publications (171)
Article
In this issue of Developmental Cell, Varapparambath et al. identify a new module that is instrumental for the selection of meristem progenitor cells in undifferentiated tissues. This module is triggered by mechanical feedback, and it integrates extracellular matrix modification, polar hormone transport, and transcription factors.
Article
Full-text available
The above-ground organs in plants display a rich diversity, yet they grow to characteristic sizes and shapes. Organ morphogenesis progresses through a sequence of key events, which are robustly executed spatiotemporally as an emerging property of intrinsic molecular networks while adapting to various environmental cues. This Review focuses on the m...
Article
Full-text available
The instructive role of mechanical cues during morphogenesis is increasingly being recognized in all kingdoms. Patterns of mechanical stress depend on shape, growth and external factors. In plants, the cell wall integrates these three parameters to function as a hub for mechanical feedback. Plant cells are interconnected by cell walls that provide...
Preprint
Full-text available
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 sto...
Article
Full-text available
The plasma membrane is a physical boundary made of amphiphilic lipid molecules, proteins and carbohydrates extensions. Its role in mechanotransduction generates increasing attention in animal systems, where membrane tension is mainly induced by cortical actomyosin. In plant cells, cortical tension is of osmotic origin. Yet, because the plasma membr...
Article
Full-text available
To survive, cells must constantly resist mechanical stress. In plants, this involves the reinforcement of cell walls, notably through microtubule-dependent cellulose deposition. How wall sensing might contribute to this response is unknown. Here, we tested whether the microtubule response to stress acts downstream of known wall sensors. Using a mul...
Article
Full-text available
As scientists, we are at least as excited about the open questions—the things we don’t know—as the discoveries. Here, we asked 15 experts to describe the most compelling open questions in plant cell biology. These are their questions: How are organelle identity, domains, and boundaries maintained under the continuous flux of vesicle trafficking and...
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Quantitative plant biology is an interdisciplinary field that builds on a long history of biomathematics and biophysics. Today, thanks to high spatiotemporal resolution tools and computational modelling, it sets a new standard in plant science. Acquired data, whether molecular, geometric or mechanical, are quantified, statistically assessed and int...
Article
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In multicellular organisms, sexual reproduction requires the separation of the germline from the soma. In flowering plants, the female germline precursor differentiates as a single spore mother cell (SMC) as the ovule primordium forms. Here, we explored how organ growth contributes to SMC differentiation. We generated 92 annotated 3D images at cell...
Article
Full-text available
Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) is a low-abundance membrane lipid essential for plasma membrane function1,2. In plants, mutations in phosphatidylinositol 4-phosphate (PI4P) 5-kinases (PIP5K) suggest that PI(4,5)P2 production is involved in development, immunity and reproduction3–5. However, phospholipid synthesis is highly intrica...
Preprint
To survive, cells must constantly resist mechanical stress. In plants, this involves the reinforcement of cell walls, notably through microtubule-dependent cellulose deposition, and thus wall sensing. Several receptor-like kinases have been proposed to act as mechanosensors. Here we tested whether the microtubule response to stress acts downstream...
Article
Full-text available
Because plant cells are glued to each other via their cell walls, failure to coordinate growth among adjacent cells can create cracks in tissues. Here, we find that the unbalanced growth of inner and outer tissues in the clavata3 de-etiolated3 (clv3 det3) mutant of Arabidopsis thaliana stretched epidermal cells, ultimately generating cracks in stem...
Article
Full-text available
Significance During development, growth deforms tissues and organs. This is notably the case during the formation of new flowers in plants, as the tissue folds during young floral bud emergence. Here, we provide further evidence that organogenesis compresses the cells at the boundary, separating the organ from the stem cell niche, and we show that...
Article
Plants produce organs of various shapes and sizes. While much has been learned about genetic regulation of organogenesis, the integration of mechanics in the process is also gaining attention. Here, we consider the role of forces as instructive signals in organ morphogenesis. Turgor pressure is the primary cause of mechanical signals in developing...
Article
Tissue folding is a central building block of plant and animal morphogenesis. In dicotyledonous plants, hypocotyl folds to form hooks after seedling germination that protects their aerial stem cell niche during emergence from soil. Auxin response factors and auxin transport are reported to play a key role in this process. Here, we show that the mic...
Article
Full-text available
Tissue bending is vital to plant development, as exemplified by apical hook formation during seedling emergence by bending of the hypocotyl. How tissue bending is coordinated during development remains poorly understood, especially in plants where cells are attached via rigid cell walls. Asymmetric distribution of the plant hormone auxin underlies...
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Full-text available
Significance In plants, microtubules largely determine the direction of cell expansion and the orientation of cell division planes. However, what processes orient the microtubules has remained debated. Here, we used microfabricated wells to confine and deform wallless plant cells in a controlled way to analyze the response of microtubules to cell g...
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Full-text available
Beyond its biochemical nature, the nucleus is also a physical object. There is accumulating evidence that its mechanics plays a key role in gene expression, cytoskeleton organization, and more generally in cell and developmental biology. Building on data mainly obtained from the animal literature, we show how nuclear mechanics may orchestrate devel...
Article
Full-text available
Beyond its biochemical nature, the nucleus is also a physical object. There is accumulating evidence that its mechanics plays a key role in gene expression, cytoskeleton organization, and more generally in cell and developmental biology. Building on data mainly obtained from the animal literature, we show how nuclear mechanics may orchestrate devel...
Preprint
In multicellular organisms, sexual reproduction requires the separation of the germline from the soma. In flowering plants, the first cells of the germline, so-called spore mother cells (SMCs), differentiate as the reproductive organs form. Here, we explored how organ growth influences and contributes to SMC differentiation. We generated a collecti...
Article
Although the ‘rebound effect’ is well established in environmental economics, the sometimes paradoxical effects of yield increase are rarely questioned within the plant science community. Acknowledging the curse of efficiency can help us to reframe our societal goals from performance at all cost to resilience.
Article
Full-text available
Organ size and shape are precisely regulated to ensure proper function. The four sepals in each Arabidopsis thaliana flower must maintain the same size throughout their growth to continuously enclose and protect the developing bud. Here we show that DEVELOPMENT RELATED MYB-LIKE 1 (DRMY1) is required for both timing of organ initiation and proper gr...
Preprint
Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P 2 ] is a low abundant lipid present at the plasma membrane of eukaryotic cells. Extensive studies in animal cells revealed the pleiotropic functions of PI(4,5)P 2 . In plant cells, PI(4,5)P 2 is involved in various cellular processes including the regulation of cell polarity and tip growth, clathrin-m...
Article
Full-text available
Human societies rely on rules to function, curbing the interests of individuals in favor of the interests of the population. A review of recent progress in biology and digital sciences suggests that such strategies might be universal: many living and technological systems favor the interests of the population to the detriment of individuals, at all...
Article
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Background: Upon water uptake and release of seed dormancy, embryonic plant cells expand, while being mechanically constrained by the seed coat. Cortical microtubules (CMTs) are key players of cell elongation in plants: their anisotropic orientation channels the axis of cell elongation through the guidance of oriented deposition of load-bearing ce...
Article
In animal single cells in culture, nuclear geometry and stiffness can be affected by mechanical cues, with important consequences for chromatin status and gene expression. This calls for additional investigation into the corresponding physiological relevance in a multicellular context and in different mechanical environments. Using the Arabidopsis...
Preprint
Full-text available
Organs precisely regulate their size and shape to ensure proper function. The contribution of organ initiation timing to final organ size and shape is often masked by compensatory adjustments to growth later in development. Here we show that DEVELOPMENT RELATED MYB-LIKE1 (DRMY1) is required for both proper organ initiation timing and growth leading...
Preprint
Tissue folding is a central building block of plant and animal morphogenesis. In dicotyledonous plants, hypocotyl folds to form hook after seedling germination that protects their aerial stem cell niche during emergence from soil. Auxin response factors and auxin transport are classically thought to play a key role in this process. Here we show tha...
Article
Growth variability generates mechanical conflicts in tissues. In plants, cortical microtubules usually align with maximal tensile stress direction, thereby mechanically reinforcing cell walls, and channeling growth rate and direction. How this is achieved remains largely unknown and likely involves microtubule regulators. The NIMA-related microtubu...
Article
Full-text available
Flowering plants are the foundation of human civilization, providing biomass for food, fuel, and materials to satisfy human needs, dependent on fertile soil, adequate water, and favorable weather. Conversely, failure of any of these inputs has caused catastrophes. Today, human appropriation of biomass is threatening planetary boundaries, inducing s...
Article
In multicellular organisms, sexual reproduction requires the separation of the germline from the soma. In flowering plants, the first cells of the germline, so-called spore mother cells (SMCs), differentiate as the reproductive organs form. Here, we explored how organ growth influences and contributes to SMC differentiation. We generated a collecti...
Article
Full-text available
Mechanical signals play many roles in cell and developmental biology. Several mechanotransduction pathways have been uncovered, but the mechanisms identified so far only address the perception of stress intensity. Mechanical stresses are tensorial in nature, and thus provide dual mechanical information: stress magnitude and direction. Here we propo...
Article
Full-text available
While accumulating evidence suggests that gene regulation is highly stochastic, genetic screens successfully uncovered master developmental regulators, questioning the relationship between transcriptional noise and intrinsic robustness of development. Here we use the Arabidopsis Paf1c mutant vip3, which is impaired in several RNA Pol II-dependent t...
Chapter
Analysis of meristem shape and gene expression pattern has been conducted in many species over the past decades. Recent live imaging techniques have allowed for an unprecedented accumulation of data on the biology of meristematic cells, as well as a better understanding of the molecular and biophysical mechanisms behind shape changes in this tissue...
Article
Full-text available
Background Many methods have been developed to quantify cell shape in 2D in tissues. For instance, the analysis of epithelial cells in Drosophila embryogenesis or jigsaw puzzle-shaped pavement cells in plant epidermis has led to the development of numerous quantification methods that are applied to 2D images. However, proper extraction of 2D cell c...
Article
Full-text available
Genetic heterogeneity and homogeneity are associated with distinct sets of adaptive advantages and bottlenecks, both in developmental biology and population genetics. Whereas populations of individuals are usually genetically heterogeneous, most multicellular metazoans are genetically homogeneous. Observing that resource scarcity fuels genetic hete...
Article
Full-text available
Many plants grow organs and tissues with twisted shapes. Arabidopsis mutants with impaired microtubule dynamics exhibit such a phenotype constitutively. Although the activity of the corresponding microtubule regulators is better understood at the molecular level, how large-scale twisting can emerge in the mutants remains largely unknown. Classicall...
Data
Cell curling in qua1-1 spr2-2. 360 degree rotation from the sample presented in Figure 3E.
Data
Cell curling in qua1-1 spr2-2. 360 degree rotation from the sample presented in Figure 3G.
Data
Cell curling in qua1-1. 360 degree rotation from the sample presented in Figure 3D.
Data
Cell curling in qua1-1. 360 degree rotation from the sample presented in Figure 3C.
Article
Full-text available
The control of cell position and division act in concert to dictate multicellular organization in tissues and organs. How these processes shape global order and molecular movement across organs is an outstanding problem in biology. Using live 3D imaging and computational analyses, we extracted networks capturing cellular connectivity dynamics acros...
Data
Video S1. Animation Showing Cellular Connectivity Network of the Arabidopsis SAM, Related to Figure 1
Book
Analysis of meristem shape and gene expression pattern has been conducted in many species over the past decades. Recent live imaging techniques have allowed for an unprecedented accumulation of data on the biology of meristematic cells, as well as a better understanding of the molecular and biophysical mechanisms behind shape changes in this tissue...
Article
Microcracks in materials reflect their mechanical properties. The quantification of the number or orientation of such cracks is thus essential in many fields, including engineering and geology. In biology, cracks in soft tissues can reflect adhesion defects, and the analysis of their pattern can help to deduce the magnitude and orientation of tensi...
Chapter
Morphogenesis involves coordinated cell division and cellular growth. Beyond average growth rate and direction, multicellular growth can also be characterized by its variance, i.e., the level of heterogeneity between individual cells or regions. Because final shapes are usually very reproducible, this raises the question of the contribution of loca...
Article
Development is remarkably reproducible, producing organs with the same size, shape, and function repeatedly from individual to individual. For example, every flower on the Antirrhinum> stalk has the same snapping dragon mouth. This reproducibility has allowed taxonomists to classify plants and animals according to their morphology. Yet these reprod...
Article
Full-text available
Mechanical forces have emerged as coordinating signals for most cell functions. Yet, because forces are invisible, mapping tensile stress patterns in tissues remains a major challenge in all kingdoms. Here we take advantage of the adhesion defects in the Arabidopsis mutant quasimodol (qual) to deduce stress patterns in tissues. By reducing the wate...
Article
A new study uncovers the role of wall sensing and remodeling in the plant response to salt stress, identifying the FERONIA receptor kinase as a key player in that process, likely through direct sensing of cell wall pectins.
Data
Average cell area and LEC area for wt and spk1 cotyledon time-course. This table contains average values for 20% largest segmented cells (in each sample), displayed in Figure 5A.
Data
Mean average cell area for wild type and spk1 cotyledon cells (20% largest segmented cells for each sample, averaged), displayed in Figure 5—figure supplement 3.
Data
Average cell area and lobeyness for all studied species. Number of cells measured for each species, average values and SE are included. Figure supplements (captions embedded in the text alongside primary figures).
Article
Full-text available
Many cell functions rely on the ability of microtubules to self-organize as complex networks. In plants, cortical microtubules are essential to determine cell shape as they guide the deposition of cellulose microfibrils, and thus control mechanical anisotropy of the cell wall. Here we analyze how, in turn, cell shape may influence microtubule behav...
Data
Influence of directional cues on the average anisotropy of the network. Simulations in an ellipsoidal cell with a circumferential cue. (A) Anisotropy as a function of the strength of the signal, bd. (B-E) Snapshots showing the microtubules in half the cell (the half to the back was removed for clarity). The strength, bd, of the signal is: 0.1% (B),...
Data
Typical simulation with external cue. Ellipsoid cell shape with the following parameters for microtubule dynamics: np = 2.4 ⋅ 10−7, ns = 10−3, α = 40.1°, weak anchoring, bd = 0.02; the duration of the movie is 5000 time steps. The microtubules are shown in half the cell (the half to the back was removed for clarity). (AVI)
Data
Typical simulation. Smooth “square” cell shape with the default parameter for microtubule dynamics and weak anchoring. The duration of the movie is 5000 timesteps. (AVI)
Data
Calculation of anisotropy. (A) Smooth “square” cell shape. (B) Microtubules. (C) Unit vectors are shown as small white arrows plotted at the center of each cube. (D) The matrix M corresponding to each cube (see Methods) is diagonalised; the red vectors point in the direction of the eigenvectors and the length of the red vectors is proportional to t...
Article
Full-text available
Background In plants, the shoot apical meristem (SAM) has two main functions, involving the production of all aerial organs on the one hand and self-maintenance on the other, allowing the production of organs during the entire post-embryonic life of the plant. Transcription factors, microRNA, hormones, peptides and forces have been involved in meri...