|
|
|
|
|
|
|
||
Olivier HAMANT
DR INRAE
Publications
Jan TRAAS
DR INRAE
Christophe TREHIN
MC UCBL
Marjolaine MARTIN
TR ENS
Claire Lionnet
IE CNRS
Duy-Chi TRINH
Post Doc INRAE
Juan ALONSO-SERRA
Post Doc EMBO
Alice MALIVERT
PhD student
Paula LLANOS
Visiting Scientist (Jacques Dumais lab)
Annalisa BELLANDI
annalisa.bellandi
Post doc INRAE
Antoine CHEVALLIER
PhD student
Charlotte KIRCHHELLE
CR INRAE - ERC Project leader "EDGE-CAM"
Denise ARICO
denise.arico
Post doc
Isaty MELOGNO
PhD student
Johanna DICKMANN
Postdoc INRAE
Liam ELLIOTT
Postdoc INRAE
Mariana ROMEIRO MOTTA
mariana.romeiro_motta
Post doc INRAE
Marianne LANG
PhD student
Sana DIEUDONNE
sana.dieudonne
Ingénieur de Recherche
Shogo TAKATANI
Post Doc HFSP (LTF)
Shouling XU
shouling.xu
Collaborateur bénévole
Sofia CORREA
PhD student
Xinyu ZHANG
Postdoc INRAE
Zoe NEMEC VENZA
zoe.nemec_venza
Post doc INRAE
2023
Preprints, Working Papers, ...
2022
Journal articles
2021
Journal articles
2020
Journal articles
Book sections
Preprints, Working Papers, ...
2019
Journal articles
Book sections
2018
Journal articles
2017
Journal articles
Book sections
2016
Journal articles
2015
Journal articles
2014
Journal articles
Book sections
2013
Journal articles
2012
Journal articles
2011
Journal articles
2010
Journal articles
2009
Journal articles
2008
Journal articles
2006
Journal articles
** 1 PhD position available (in collaboration), see pdf below **
Plant organ morphogenesis: geometry calls for biochemistry and mechanics
Changing shape is changing structure. By definition, this involves the laws of mechanics. Not only do plant generate diverse shapes, but shape itself can serve as an instructive cue to channel morphogenesis, through biochemical and mechanical signaling.
New scientific questions: robustness, multiscale hierarchy, emergent properties
How do organs know when to stop growing? How do multicellular organisms produce their diverse shapes? The underlying process, morphogenesis, is complex and characterised by three remarkable features: robustness, hierarchy, and emergence. Morphogenesis robustly produces highly similar forms across a wide range of conditions, despite and sometimes thanks to high levels of local variability. Morphogenesis involves events on a hierarchy of different scales in time and space (from the molecular to the organ scale). Individual factors contributing to morphogenetic events have been studied extensively, but are insufficient to fully predict morphogenesis – morphogenesis has emergent properties. Therefore, a central and challenging question in biology is how different factors are integrated and coordinated across multiple spatio-temporal scales to robustly produce organ shapes.
1. Cell Edges and Morphogenesis
Plants face a particular challenge when forming new organs: their cells share a rigid cell wall, which requires adjacent cells to coordinate their growth.
Growth patterns in Arabidopsis lateral roots
Directional growth depends on differences in cell wall mechanical properties in different regions of the cell. To establish and modulate these, cells precisely coordinate the transport of different cell wall components and their associated biosynthetic machinery to different regions of the cell surface.
Cell edges are a biochemically distinct domain in plant cells. Cell wall biosynthesis involves multiple trafficking pathways to the cell surface, which are regulated by Rab GTPases. RAB-A5c mediates a trafficking pathway specifically to cell edges in Arabidopsis lateral roots.
Our team is particularly interested in cell edges, the geometric domain at the intersection of two cell faces. Our previous work has shown that plants specify a transport route to cell edges which required for directional growth, but does not act through oriented cellulose deposition, the leading paradigm for directional growth control.
In our current work funded by ERC Starting Grant EDGE-CAM, we try to understand why cell edges are important during morphogenesis, and how plant cells specify their edges as distinct domains.
Why cell edges are important during morphogenesis? Cell edges are notable domains from a topological, geometric, and mechanical perspective. With respect to mechanics, they accumulate stresses arising at the cell level through turgor pressure, and are also exposed to shear stresses arising through differential growth at the tissue scale. We hypothesise that plants specify a cell wall sensing module at cell edges through which they can monitor the mechanical status at the cell wall and adapt growth through fine-tuning trafficking pathways. We are combining forward genetics, proteomics, quantitative imaging, and computational modelling to test our hypothesis and identify new components of edge-based growth control.
A multi-scale model for robust morphogenesis. [1] An RLP-based cell wall sensing module at cell edges senses cell wall changes associated with tissue-level mechanics. [2] Downstream targets of the cell wall sensing module include endomembrane trafficking pathways involved in cell wall assembly. [3] Activity of these pathways determines cellular growth patterns and tissue-level mechanical constraints.
How plant cells specify their edges as distinct domains? Protein localisation to cell edges has been linked to cytoskeleton organisation and the status of the cell wall, however it is an open question how plant cells identify their edges or differentiate between different edges in the same cell. We are exploring mechanical, geometric, and biochemical factors that may contribute to the recruitment of proteins to cell edges using quantitative imaging and genetics in planta and in an in vitro single-cell system.
Associated team members:
Charlotte Kirchhelle
Antoine Chevallier
Liam Elliott
Claire Lionnet
Marjolaine Martin
Zoe Nemec Venza
Xinyu Zhang
2. Multiscale microtubule response to stress
In past work, we showed that cortical microtubules align along maximal tensile stress directions, thereby reinforcing cell walls through the guidance of cellulose deposition.
Cortical microtubules also guide the orientation of the next division plane (through the preprophase band). Combining modeling and experiments, we formally showed that tensile stress prescribes cell division plane orientation. We also unraveled a role of microtubule dynamics and response to stress in organ initiation in organ shape robustness, in organ growth arrest and in organ flatness.
Confined protoplasts in microwells
We are now investigating the possibility that microtubules may be their own mechanosensors, notably using in vitro and microfabrication techniques, such as confined protoplasts in microwells.
In planta, this response may have important implications, relating mechanical conflicts due to differential growth to morphogenesis.
CreLox lines inducing growth mosaics and artificial mechanical conflicts at the shoot apex
Associated team members:
Olivier Hamant
Antoine Chevallier
Leia Colin
Charlotte Kirchhelle
Claire Lionnet
Alice Malivert
Marjolaine Martin
Isaty Melogno
Shogo Takatani
Jan Traas
3. Mechanical identity
Beyond the cell cortex, we started to analyze the impact of mechanical signals on gene expression. We found that the expression of key transcription factors (CUC3 and STM) is in part under mechanical control.
STM expression in meristem boundaries, stress hotspots (Landrein et al., 2015)
The nexus between mechanical signals at the cell cortex and gene expression may involve different pathways. Recently, we started to analyze the role of nucleus deformation in gene expression.
We are also investighating the role of the RNA Polymerase-associated factor 1 complex (Paf1c), a central regulator of transcription, in development, at the nexus between transcriptional noise and developmental robustness. We found that Paf1c-dependent transcription contributes to the robustness of phyllotaxis and flower termination. Although at this stage it remains difficult to link mechanosensing with these phenotypes, these results open the possibility for crosstalks between transcriptional noise, mechanotransduction and development.
Severe indetermincay defects in the Paf1c mutant
Associated team members:
Olivier Hamant & Christophe Tréhin
Johanna Dickmann
Juan Alonso Serra
Marianne Lang
Claire Lionnet
Marjolaine Martin
Duy-Chi Trinh
4. Science and society
We are also involved in science-society projects, notably on the environmental question sustainability and in several art-science projects. This notably includes the question of robustness.
The industrial agricultural model is based on a reduced quantity of genetically homogeneous varieties. In wheat, many species have contributed to the human diet since their domestication, but only certain pure lines of common wheat (Triticum aestivum) and durum wheat (T. durum) are now widely distributed. However, they are not very robust to climate change, have low micronutrient contents and are the source of intolerance. However, there are so-called “old” or “marginal” cereals. Abandoned by industrial agriculture, these have escaped associated selection. Thus, they have retained resistance traits, genetic diversity allowing their adaptation and interesting nutritional properties. Many varieties of small (T. monococcum), medium (T. dicoccum), and great spelled (T. spelta), closely related to soft and hard wheats, are part of these cereals. Now cultivated on a small scale, they appear to be good candidates for restoring a certain biodiversity in wheat.
Emmer grown at CRBA, Charly
The case of pollard trees or trunks, of which all the upper and lateral branches are pruned, illustrates the remarkable plant plasticity. The trunks indeed develop a characteristic phenotype with an increased trunk thickness and massive repetitions of shoots. Since the Neolithic, this rural practice has been an essential source of renewable wood and fodder, before declining with the advent of the modern era. Conventional agriculture is increasingly under the spotlight for its negative externalities (greenhouse gas emissions,
pollution, dependence on fossil fuels, loss of biodiversity, desertification ...) and for its low resilience. From this perspective, the pollards find a new agronomic relevance.
Pollard tree drawing
Last, we are also investigating the potential use of plant cell walls as metamaterials, notably their phononic properties. There are numerous examples of animals that manipulate visible light for functional purposes, such as insect wings made of hexagon arrays of cone-shaped nanopillars that provide a graded refractive index for camouflage. Such photonic structures can be mimicked to find innovative solutions for light control in nano- to microstructures. In contrast, there has been no observation of phonon-based biological functions at the supramolecular scale, making phononic bioinspired strategies inoperative. Thomas Dehoux team has recently demonstrated that biological composites in the form of decellularized plant cell scaffolds can behave as phononic materials, including forbidding the propagation of elastic waves in select frequency ranges (i.e. band gaps). This opens the possibility for biobased phononic materials (BPM).
Propagation of an acoustic wave in an onion epidermal peel (T. Dehoux team)
Associated team members:
Olivier Hamant
Sofia Correa
Sana Dieudonné
Marianne Lang
To explore more science & society questions, visit the Michel Serres Institute website: https://institutmichelserres.fr/
2020 Hamant O*, Saunders TE* (2020) Shaping Organs: Shared Structural Principles Across Kingdoms. Annu Rev Cell Dev Biol. Long Y*, Cheddadi I, Mosca G, Mirabet V, Dumond M, Kiss A, Traas J, Godin C, Boudaoud A* (2020) Cellular Heterogeneity in Pressure and Growth Emerges from Tissue Topology (...)
L’architecture de la plante dépend pour une grande partie de groupes de cellules souches appelés méristèmes, qui initient les organes et en déterminent la position.
Les méristèmes définissent donc un certain nombre de traits d’intérêt agronomique évident, d’où l’importance d’étudier et comprendre leur (...)