Gilles Dupouy

Yihan Dong

Etienne Herzog

Marie-Edith Chabouté
email: marie-edith.chaboute@ibmp-cnrs.unistra.fr

Alexandre Berr
email: alexandre.berr@ibmp-cnrs.unistra.fr

Nuclear envelope dynamics in connection to chromatin remodeling

Keywords: nuclear envelope, cytoskeleton, nucleoskeleton, mechanical cues, chromatin, epigenetics

à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

The nucleus is a central organelle in eukaryotic cells, where the nuclear envelope (NE) compartmentalizes chromatin by mean of two phospholipid bilayer membranes. The outer nuclear membrane (ONM) is derived from the endoplasmic reticulum (ER) and is separated from the inner nuclear membrane (INM) by a perinuclear space of about 30-50 nm [START_REF] Stewart | Blurring the boundary: the nuclear envelope extends its reach[END_REF]. The INM is connected to the nucleoskeleton, a filamentous meshwork of 10-30 nm, composed primarily of lamins in animals, with functional analogs in plants and fungi [START_REF] Ciska | The intriguing plant nuclear lamina[END_REF]. The NE is perforated by nuclear pore complexes (NPCs) allowing molecular exchanges between nucleus and cytoplasm. Peripheral nucleoskeleton and NPCs allow chromatin tethering at the nuclear periphery and are required for proper genome organization and activity [START_REF] Boruc | Dynamics of the plant nuclear envelope and nuclear pore[END_REF][START_REF] Bi | Nonrandom domain organization of the Arabidopsis genome at the nuclear periphery[END_REF][START_REF] Hu | Plant lamin-like proteins mediate chromatin tethering at the nuclear periphery[END_REF]Tang et al., 2022a;Tang et al., 2022b). The nucleoskeleton is also connected to the cytosol and the cytoskeleton through NPCs and Linker of Nucleoskeleton and Cytoskeleton (LINC) complexes [START_REF] Zhou | The plant nuclear envelope as a multifunctional platform LINCed by SUN and KASH[END_REF][START_REF] Kirby | Emerging views of the nucleus as a cellular mechanosensor[END_REF]. In animals, cytoskeleton networks extend towards the cell periphery with the assembly of actin microfilaments (MFs) at the cellular cortex [START_REF] Chugh | The actin cortex at a glance[END_REF]. Conversely, in walled plant cells, microtubules (MTs) are mainly present at the cortex to control cell shape through cellulose deposition while MFs are mostly involved in vesicle trafficking and organelle movements [START_REF] Smith | Cytoskeletal control of plant cell shape: getting the fine points[END_REF]. Another specific feature of acentrosomal plant cells is that the NE acts as a Microtubule-Organizing Center (MTOC) forming radial MT arrays extending through the cytoplasm which reorganize during pre-spindle assembly upon mitosis entry [START_REF] Masoud | Microtubule nucleation and establishment of the mitotic spindle in vascular plant cells[END_REF]Ambrose and Wasteneys, 2014). Finally, intermediate filaments (IFs) form an intricate network of complex filamentous structures, exclusively found in animals, that extends from the cell membrane to the nucleus.

IFs are master integrators of cell and tissue mechanics (van Bodegraven and Etienne-Manneville, 2021) and rearrange themselves to serve as stress buffers (Sanghvi- [START_REF] Sanghvi-Shah | Intermediate Filaments at the Junction of Mechanotransduction, Migration, and Development[END_REF].

All living organisms perceive mechanical cues from their environment and integrate them at the cellular level to respond and to adjust their behaviour for proper development and survival [START_REF] Tsata | In Full Force. Mechanotransduction and Morphogenesis during Homeostasis and Tissue Regeneration[END_REF]. Both external and internal mechanical stimuli induce cellular deformation and/or constraints which are sensed at the cell periphery and transduced in biochemical and mechanical responses. Cytoskeleton reorganization and chromatin structural changes participate in such mechano-transduction and influence all genomic functions including transcriptional gene expression programs [START_REF] Graham | Mechanotransduction and nuclear function[END_REF]Fal et al., Cells interact physically with their environment and can perceive mechanical constraints. These mechanical cues are sensed at the cell periphery and transmitted to the nucleus to be converted into coordinated cellular responses. This relies on specific subcellular structures in animal cells and walled plant cells, especially at the nucleo-cytoplasmic interface (Figure 1).

Mechanosensing at the cell periphery

In animals, cells can be constrained during migration and/or tissue morphogenesis, but also in response to external mechanical forces. Such forces are driven by the stiffness of the surrounding extracellular matrix inducing deformations of the plasma membrane [START_REF] Shin | Squeezing cells through the epigenetic machinery[END_REF] which may regulate gene expression through direct force transmission and chromatin stretching [START_REF] Joshi | The role of cellular traction forces in deciphering nuclear mechanics[END_REF]. Cell geometric constraints can also be obtained using micropatterned substrates, inducing cellular shape changes which are transmitted to the nucleus through cytoskeletal physical links (Alisafaei et al., 2019). Resulting mechanical signals are sensed by focal adhesion complexes, mainly formed by transmembrane proteins of the integrin family that connect the plasma membrane to the extracellular matrix and transmit mechanical tension to the actin-myosin cytoskeleton. Cell-cell junctions with cadherins are also key mechanosensitive modules [START_REF] Mathieu | Intracellular mechanics: connecting rheology and mechanotransduction[END_REF]. In parallel, mechanosensitive (MS) ion channels embedded in the plasma membrane, such as Piezo1 and 2, integrate various mechanical cues typically by increasing cytoplasmic Ca 2+ concentration. Their activation mainly triggers cytoskeleton modulation [START_REF] Qin | Roles of mechanosensitive channel Piezo1/2 proteins in skeleton and other tissues[END_REF]. Interestingly, Piezo1 is also present at the endoplasmic reticulum (ER) and there, upon cell stretching, can mediate heterochromatin reduction via Ca 2+ release from the ER, thus promoting chromatin mobility and decreasing NE tension [START_REF] Nava | Heterochromatin-Driven Nuclear Softening Protects the Genome against Mechanical Stress-Induced Damage[END_REF].

In plants, the high turgor pressure (around the Mpa range) is the primary cause of mechanical stress during plant development as it exerts pulling forces on cell walls [START_REF] Trinh | How Mechanical Forces Shape Plant Organs[END_REF].

Cell wall deformation and remodeling can also transduce external mechanical signals for changes in gene expression as observed at the boundary region of the shoot apical meristem [START_REF] Landrein | Mechanical stress contributes to the expression of the STM homeobox gene in Arabidopsis shoot meristems[END_REF]. Similarly, touching seedlings lead to an increase of cell wall stiffness and a decrease of cell elongation, together resulting in the modulation of the expression of touch-responsive genes [START_REF] Wu | Touch-induced seedling morphological changes are determined by ethylene-regulated pectin degradation[END_REF]. In this context, plant mechano-sensing and transduction at the cell periphery begin to be elucidated [START_REF] Trinh | How Mechanical Forces Shape Plant Organs[END_REF], with Ca 2+ signaling also playing a central role [START_REF] Hamilton | Mechanosensitive channel MSL8 regulates osmotic forces during pollen hydration and germination[END_REF]. At the plasma membrane, MS ion channels named Mid1-complementing activity (MCA) 1 and 2 correlate with Ca 2+ influx and mechanosensing in Arabidopsis roots [START_REF] Nakagawa | Arabidopsis plasma membrane protein crucial for Ca2+ influx and touch sensing in roots[END_REF]. Also at the plasma membrane, the receptor-like kinase FERONIA (FER) acts as a mechanosensor regulating Ca 2+ signaling and the expression of touch responsive genes [START_REF] Shih | The receptor-like kinase FERONIA is required for mechanical signal transduction in Arabidopsis seedlings[END_REF][START_REF] Feng | The FERONIA Receptor Kinase Maintains Cell-Wall Integrity during Salt Stress through Ca(2+) Signaling[END_REF]. Contrary to animals, Piezo1 and 2 locate exclusively to the vacuole tonoplast in Arabidopsis [START_REF] Radin | Plant PIEZO homologs modulate vacuole morphology during tip growth[END_REF]. Because the tonoplast may have more freedom of movement than the plasma membrane in walled plant cells, locating certain mechanosensory proteins to the tonoplast might be more effective for mechanosensing [START_REF] Radin | Plant PIEZO homologs modulate vacuole morphology during tip growth[END_REF].

Importance of MFs and MTs dynamics in mechano-transduction

In vitro, both MFs and MTs polymerize faster under tensile stress [START_REF] Trinh | How Mechanical Forces Shape Plant Organs[END_REF] and MFs branch upon compression-induced bending [START_REF] Risca | Actin filament curvature biases branching direction[END_REF]. In animals, the influence of cytoskeleton organization on nuclear morphology and chromatin dynamics in driving cell differentiation is nowadays well documented. For example, during early differentiation of human hematopoietic stem cells, MT constraints induce nuclear invaginations associated with heterochromatin reorganization and modification in expression of specific hematopoietic genes [START_REF] Biedzinski | Microtubules deform the nucleus and force chromatin reorganization during early differentiation of human hematopoietic stem cells[END_REF]. Similarly, cytoskeleton components were found to shape nucleus of mouse embryonic stem (ES) cells and to influence interactions of the pluripotency transcription factor OCT4 with chromatin, thus potentially affecting pluripotency [START_REF] Romero | Nucleus-cytoskeleton communication impacts on OCT4-chromatin interactions in embryonic stem cells[END_REF].

At the plant cellular cortex, the cytoskeleton reorganization is also driven by mechanical stress, with a major role for cortical MTs as tension sensors, able to align along the maximal tensile stress directions in tissues [START_REF] Hamant | Developmental patterning by mechanical signals in Arabidopsis[END_REF][START_REF] Hamant | Are microtubules tension sensors?[END_REF]. Organogenesis of plant cells within their tissue context, along with the regulation of cell wall plasticity, can also generate compression forces. At the boundary between the central shoot apical meristematic zone and the developing organ primordia region, nuclear compression was observed with changes in heterochromatin organization and gene expression [START_REF] Landrein | Mechanical stress contributes to the expression of the STM homeobox gene in Arabidopsis shoot meristems[END_REF]Fal et al., 2021a). Together with the key role played by MTs in integrating mechanical stress to coordinate patterns of apical morphogenesis at the Arabidopsis shoot apex [START_REF] Hamant | Developmental patterning by mechanical signals in Arabidopsis[END_REF], this highlights the importance of MT reorganization for cellular shaping upon mechanical stress in plants.

The NE as a continuum between nucleoplasm and cytoplasm

The NE contains many protein complexes linking cytoskeleton and nucleoskeleton. We describe hereafter key NE components and their respective functional implications by emphasizing differences and peculiarities between animals and plants, notably in terms of mechanical stress response (see Figure 2 and Table 1).

NPCs, responsive gateways at the nucleo-cytoplasmic interface

NPCs are huge protein conglomerates (40-120 MDa) tunneling the NE at regular intervals where the ONM and INM are fused. NPCs are composed of hundreds of nucleoporin proteins (NUPs) assembled in a cylinder subdivided in four main substructures, namely the cytoplasmic filaments, the outer and inner rings forming the core component and the nuclear basket (Lin and Hoelz, 2019) (see Figure 2). NPCs selectively control the nucleocytoplasmic movement of macromolecules such as proteins and messenger ribonucleoproteins across the NE, thereby playing a key role in regulating gene expression and protein synthesis [START_REF] Walde | The Part and the Whole: functions of nucleoporins in nucleocytoplasmic transport[END_REF]. While mechanisms underlying NPC transport selectivity remain elusive, recent evidences support that their structural and constituent dynamics may serve as a strategy to adjust NPC transport capacity under different cellular and physiological conditions [START_REF] Hakhverdyan | Dissecting the Structural Dynamics of the Nuclear Pore Complex[END_REF]. In animals and yeast, NPC density is constant over a range of nuclear sizes. Nevertheless, altered NPC composition can affect nuclear size and morphology [START_REF] Jevtic | Sizing and shaping the nucleus: mechanisms and significance[END_REF]. Among other functions, NPCs, especially via their nuclear basket, are involved in regulating genomic functions by controlling chromatin organization and spatial arrangement [START_REF] Krull | Protein Tpr is required for establishing nuclear poreassociated zones of heterochromatin exclusion[END_REF][START_REF] Kadota | Nucleoporin 153 links nuclear pore complex to chromatin architecture by mediating CTCF and cohesin binding[END_REF]. Interestingly, many NUPs also have DNArelated functions inside the nucleoplasm, irrespective of their structural role within NPCs, enabling them to dynamically, rather than permanently, associate to the NPCs [START_REF] Richards | Nucleoporins facilitate ORC loading onto chromatin[END_REF].

NPC and NUP molecular functions in plants are far less described than in animals. In Arabidopsis, the plant specific nuclear basket NUP1/NUP136 can interact with heterochromatic domains such as pericentromeric regions enriched in repressed transposing elements (TEs) or silenced protein-coding genes [START_REF] Bi | Nonrandom domain organization of the Arabidopsis genome at the nuclear periphery[END_REF]. NUP136 and the other plant specific nuclear basket component NUP82 were found to interact with the euchromatin binding factor guanylate-binding protein (GBP)-like GTPase (GBPL3). GBPL3 acts as a central connector between NPCs, nucleoskeleton, chromatin remodelers, transcription regulators and components of RNA splicing and processing machinery to coordinate gene expression during plant development and stress responses (Tang et al., 2022b). Together with a physical link with the plant nucleoskeleton protein CRWN1/2 (functional analogs of animal lamins), GBPL3 acts as a chromatin remodeler and transcriptional regulator to coordinate stress responsive gene expression (Tang et al., 2022b). Interestingly, NUP136 and CRWN1 are separately involved in nuclear shaping [START_REF] Tamura | Involvement of the nuclear pore complex in morphology of the plant nucleus[END_REF][START_REF] Tamura | Recent advances in understanding plant nuclear envelope proteins involved in nuclear morphology[END_REF]. A mutation of the plant specific NUP CPR5 (CONSTITUTIVE EXPRESSION OF PR GENES 5), present at the NPC trans-membrane ring, also leads to defects in nuclear shape and changes in gene expression [START_REF] Gu | Nuclear Pore Permeabilization Is a Convergent Signaling Event in Effector-Triggered Immunity[END_REF]. Interestingly, the mis-regulated genes in cpr5 mutants show significant overlaps with genes mis-regulated in the transcriptome of gip1gip2 mutant also showing altered nuclear shape (Goswami et al., 2020b). This highlights an intricate functional network at the NE for gene and nuclear shape regulation whose dynamic spatial orchestration still needs clarifications.

There is also evidence for a major role of NPCs in mechano-transduction in animals [START_REF] Matsuda | On the nuclear pore complex and its emerging role in cellular mechanotransduction[END_REF]. In response to mechanical forces, two related mechanisms are proposed to affect nuclear import and accumulation of some specific transcription factors.

Either the NPC diameter increases inducing structural changes of the nuclear basket or transcription factors change their conformation to increase their affinity with the nuclear transport receptor [START_REF] Matsuda | On the nuclear pore complex and its emerging role in cellular mechanotransduction[END_REF]. In fission yeast, NPC diameter was shown to vary according to NE tension [START_REF] Zimmerli | Nuclear pores dilate and constrict in cellulo[END_REF] and in mammalian cells, NPC stretching allows the shuttling of epigenetic and transcription factors, such as the mechanosensor and transducer YAP/TAZ [START_REF] Elosegui-Artola | Force Triggers YAP Nuclear Entry by Regulating Transport across Nuclear Pores[END_REF]. In plants, NPCs are important regulators of gene expression in response to stress [START_REF] Tamura | Nuclear pore complex-mediated gene expression in Arabidopsis thaliana[END_REF] but their link to mechano-transduction

have not yet been investigated.

The LINC complexes, physical links between cytoskeleton and nucleoskeleton

LINC complexes are the other main protein complexes present at the NE linking nucleoskeleton to cytoskeleton. The primary function of this link is to control nuclear positioning and movement [START_REF] Tatout | The plant LINC complex at the nuclear envelope[END_REF][START_REF] Burke | Chain reaction: LINC complexes and nuclear positioning[END_REF] (see Figure 2). The LINC complexes are composed of two transmembrane protein families, namely the Sad-1/UNC-84 (SUN) domain proteins which span the INM and interact with nuclear components, and the Cterminal Klarsicht/ANC-1/Syne-1 Homology (KASH) domain proteins which span the ONM and interact with cytoplasmic components [START_REF] Tatout | The plant LINC complex at the nuclear envelope[END_REF][START_REF] Burke | Chain reaction: LINC complexes and nuclear positioning[END_REF]. SUN proteins contain a SUN domain located at the perinuclear space that is overall well conserved across eukaryotes and a nucleoplasmic domain that is much less conserved. Compared to SUN proteins, KASH proteins are far less conserved, with the KASH domain being highly variable in sequence and size [START_REF] Meier | LINCing the eukaryotic tree of life -towards a broad evolutionary comparison of nucleocytoplasmic bridging complexes[END_REF]. The tryptophan-proline-proline (WPP)-interacting proteins (WIPs) were the first animal KASH analogs identified as being able to bind SUN proteins at the NE in Arabidopsis [START_REF] Zhou | Novel plant SUN-KASH bridges are involved in RanGAP anchoring and nuclear shape determination[END_REF]. Other KASH analogs were identified in Arabidopsis including Toll-Interleukin-Resistance KASH protein (TIK) and SUN-interacting NE proteins 1-4 (SINE1-4) [START_REF] Groves | Recent advances in understanding the biological roles of the plant nuclear envelope[END_REF]. Apart from the non-conserved KASH and2 (Burke andRoux, 2009). Similarly, WIPs and WPP interacting tail anchored proteins (WITs) oligomerize in Arabidopsis to form a LINC complex at which Myosin XI-i attaches and interacts with long cables of cytoplasmic actin [START_REF] Groves | Recent advances in understanding the biological roles of the plant nuclear envelope[END_REF]. Beside this, a more direct and tissue-specific interaction was described for stomatal guard cells in which the KASH protein SINE1 directly attaches to MFs through a LINC complex involving SUN1/2 for nuclear positioning (Zhou et al., 2014). While LINC may associate to MTs through motor proteins such as kinesin, dynein or fascin (i.e., known to promote cell migration) in animals [START_REF] Burke | Nuclei take a position: managing nuclear location[END_REF], there is no such evidence in plants.

Adding another layer of complexity, direct functional associations between LINC complexes and NPCs were reported in animal cells for the control of NPC assembly/distribution and the transport of LINC complex components [START_REF] Jahed | The LINC and NPC relationship -it's complicated![END_REF]. Reinforcing such association, SUN2, but not SUN1, was found to directly bind NUP210, forming a complex able to tether the replicative histone H3 variants H3.1/H3.2 and the chromatin reader BRD4 at the nuclear periphery to regulate gene expression during metastasis in mouse (Amin et al., 2021).

As for NPCs, LINC complexes have been identified as nuclear mechano-transduction actors, but so far only in animals [START_REF] Fal | Nuclear envelope: a new frontier in plant mechanosensing?[END_REF]. For example, forces transmitted via the KASH protein Nesprin-1 in isolated nuclei led to increased nuclear stiffness [START_REF] Guilluy | Isolated nuclei adapt to force and reveal a mechanotransduction pathway in the nucleus[END_REF].

Accordingly, NESPRINs were shown to transfer mechanical forces from actomyosin to the nucleus through LINC complexes (Arsenovic et al., 2016) and to contribute to the induction of a mechanically responsive gene program (Banerjee et al., 2014). Local stresses applied to integrins can propagate to LINC complexes through the actin cytoskeleton and lead to chromatin unpacking as well as epigenetic changes promoting transcription [START_REF] Tajik | Transcription upregulation via force-induced direct stretching of chromatin[END_REF].

Finally, in fibroblast, both SUN1 alteration and changes in substrate rigidity affect transcription (Alam et al., 2016). Inside the nucleus, both NPCs and LINC complexes interact with a thin fibrous protein meshwork closely juxtaposed between the nucleoplasmic face of the INM and the chromatin [START_REF] Figueiras | Phasor-assisted nanoscopy reveals differences in the spatial organization of major nuclear lamina proteins[END_REF] (see Figure 2). In metazoan, this meshwork is named the nuclear lamina and is mainly composed of type V IF lamin proteins (i.e., A and C-type lamins plus several minor tissue specific isoforms in most differentiated cells and B-type lamins expressed ubiquitously). Lamins play major roles in controlling nuclear rigidity and chromatin organization and are key elements for mechanosensing and nuclear mechano-transduction [START_REF] Swift | Nuclear lamin-A scales with tissue stiffness and enhances matrixdirected differentiation[END_REF][START_REF] Vahabikashi | Nuclear lamins: Structure and function in mechanobiology[END_REF]. In mammalian cells, A/C and B lamins interact with heterochromatin to form lamina-associated domains (LADs) enriched in heterochromatin at the nuclear periphery and interact as well with euchromatin domains to promote gene expression [START_REF] Vahabikashi | Nuclear lamins: Structure and function in mechanobiology[END_REF]. For example, in the progeria syndrome the accumulation of progerin, a dominant-negative A-type lamin protein, disrupts heterochromatin-lamina interactions and results in disturbed nuclear shape and spatial chromatin organization leading to gene expression alterations [START_REF] Mccord | Correlated alterations in genome organization, histone methylation, and DNA-lamin A/C interactions in Hutchinson-Gilford progeria syndrome[END_REF].

The tight connections between NE, nucleoskeleton and chromatin

In plants, no IFs or nuclear lamins were identified, but functional homologs were regrouped as nuclear matrix constituent proteins (NMCPs) [START_REF] Masuda | Peripheral framework of carrot cell nucleus contains a novel protein predicted to exhibit a long alpha-helical domain[END_REF]. NMCPs assembly produces an intricate filamentous network called plamina, including filament bundles across the nuclear periphery [START_REF] Masuda | The plant nuclear lamina proteins NMCP1 and NMCP2 form a filamentous network with lateral filament associations[END_REF]. They are widely conserved in land plants and CROWDED NUCLEI 1 to 4 (CRWN1-4), identified in Arabidopsis, belong to this family (Ciska and Moreno Diaz de la Espina, 2014). CRWN1 and 4 interact and redundantly modulate chromatin organization at the nuclear periphery through their direct binding with chromatin regions named plant LADs (PLADs) [START_REF] Hu | Plant lamin-like proteins mediate chromatin tethering at the nuclear periphery[END_REF]. This link with chromatin was further reinforced by the discovery that CRWN1 interacts with the chromatin and polycomb-associated component PROLINE-TRYPTOPHANE-TRYPTOPHANE-PROLINE INTERACTOR OF POLYCOMBS1 (PWO1), possibly linking repressive H3K27me3-marked chromatin and the nuclear periphery in Arabidopsis [START_REF] Mikulski | The Chromatin-Associated Protein PWO1 Interacts with Plant Nuclear Lamin-like Components to Regulate Nuclear Size[END_REF]. In addition, CRWN1 directly associates with SUN1 [START_REF] Graumann | Evidence for LINC1-SUN associations at the plant nuclear periphery[END_REF], while the NMCP-binding protein KAKU4 indirectly associates with SUN1 via interaction with CRWN1 [START_REF] Goto | The Novel Nuclear Envelope Protein KAKU4 Modulates Nuclear Morphology in Arabidopsis[END_REF]. CRWN1 and CRWN4

are key factors maintaining nuclear morphology. In the contrary to crwn2 or crwn3 mutants [START_REF] Wang | Arabidopsis CROWDED NUCLEI (CRWN) proteins are required for nuclear size control and heterochromatin organization[END_REF], kaku4 and crwn1 mutants exhibit drastic abnormalities in nuclear shape in differentiated tissues and their combination had neither synergistic nor additive effects [START_REF] Goto | The Novel Nuclear Envelope Protein KAKU4 Modulates Nuclear Morphology in Arabidopsis[END_REF]. The plant specific nuclear envelope-associated proteins (NEAPs) are anchored at the INM and directly interact with SUN proteins. Further connecting NEAPs with chromatin organization and gene regulation, a putative transcription factor called AtbZIP18 was identified among the NEAP interactors [START_REF] Pawar | A novel family of plant nuclear envelope-associated proteins[END_REF]. More recently, the plant NE transmembrane protein (PNET2) was identified as a bona fide INM protein interacting with CRWN1 in Arabidopsis (Tang et al., 2022a). PNET2 together with KAKU4 contribute to the proper maintenance of genome architecture and transcriptome programing during plant development and stress response. Interestingly, the simultaneous overexpression of PNET2 and KAKU4 induces more severe nuclear deformations than when they were overexpressed separately (Tang et al., 2022a). Finally, suggesting a physical link between the nucleoskeleton and NPCs, NUP82 and 136 were revealed to bind CRWN proteins [START_REF] Mermet | Evolutionary conserved protein motifs drive attachment of the plant nucleoskeleton at nuclear pores[END_REF]. Together, tight functional connections exist between cytoskeleton, NE, nucleoskeleton and NPCs to regulate gene expression in plants but the importance of the plamina in mechanical response remains to be investigated.

Chromatin remodeling upon NE dynamics and mechanical stress

Nucleosome is the main structural unit of eukaryotic chromatin and consists of DNA wrapped around a core histone octamer (2x (H2A, H2B, H3 and H4)). Chromatin is dynamically organized and can promote DNA compaction in heterochromatin or relaxation in euchromatin at different scales to affect genomic functions [START_REF] Dogan | Three-dimensional chromatin packing and positioning of plant genomes[END_REF]. Among mechanisms affecting directly or indirectly chromatin compaction, epigenetic processes, including DNA methylation, histone variant incorporation and histones post-translational modifications (PTMs) were involved in regulating all DNA related processes [START_REF] Lloyd | Epigenome plasticity in plants[END_REF][START_REF] Mansisidor | Chromatin accessibility: methods, mechanisms, and biological insights[END_REF]. On a larger scale, chromatin during interphase forms functional loop domains allowing each chromosome to occupy an individual territory.

Physically, chromatin is considered as a viscoelastic gel displaying changes in macromolecular crowding [START_REF] Mitchison | Colloid osmotic parameterization and measurement of subcellular crowding[END_REF]. In recent years, chromatin organization and dynamics has emerged as an instrument of mechanical stress response in both animals and plants [START_REF] Uhler | Regulation of genome organization and gene expression by nuclear mechanotransduction[END_REF]Goswami et al., 2020a).

Impact on constitutive heterochromatin

In both animals and plants, chromocenters are predominantly composed of silent, condensed and gene-poor pericentromeric heterochromatin, and are attached in a non-random way to the nuclear periphery via lamins or functional analogs [START_REF] Fransz | Interphase chromosomes in Arabidopsis are organized as well defined chromocenters from which euchromatin loops emanate[END_REF][START_REF] Rullens | Attach and stretch: Emerging roles for genome-lamina contacts in shaping the 3D genome[END_REF]. A recent report on epidermis stem cells highlights the fact that a majority of the observed heterochromatin decondensation induced under short time stretching tensions happens mostly in non-coding regions, resulting in no major transcriptional changes [START_REF] Nava | Heterochromatin-Driven Nuclear Softening Protects the Genome against Mechanical Stress-Induced Damage[END_REF]. More recently, a decrease of H3K9me3 constitutive heterochromatin mark levels accompanied by a decrease of DNA methylation and A/C-type lamin content at the nuclear periphery was reported after squeezing mice isolated nuclei through a microfluidic device [START_REF] Song | Transient nuclear deformation primes epigenetic state and promotes cell reprogramming[END_REF].

Based on these results, the mechanically-induced chromatin softening resulting from the constitutive heterochromatin decompaction was proposed to decrease nuclear stiffness to protect the genome against mechanical stress-induced DNA damages.

In plants, few examples illustrate the effect of mechanical forces or NE destabilization on constitutive heterochromatin but correlations with stress and chromatin/nuclear softening are fare from being clear. In Arabidopsis shoot apical meristem, tissue curvature generates nuclear compression at the boundary between organs and meristem. This nuclear compression correlates with decreases in DNA methylation and chromocenter numbers and an increase in the expression of the abiotic stress related linker histone H1.3 (Fal et al., 2021a). Upon hyperosmotic stress in root meristematic cells, while nuclei become smaller, less spherical and stiffer, the number of chromocenters was found decreased, suggesting a heterochromatin reorganization (Goswami et al., 2020b). On the contrary, the nuclear rigidity was found decreased with more diffuse heterochromatic signals upon hypoosmotic conditions (Goswami et al., 2020b). Further supporting the links between NE and constitutive heterochromatin compaction, chromocenters were also found affected in differentiated tissues when plamina and LINC complexes components were mutated. Indeed, despite similar changes in nuclear morphology (i.e., smaller but more spherical), an increased compaction of chromocenters in crwn1crwn2 mutants correlates with a maintenance of their transcriptional silencing, while altering LINC complexes causes chromocenter decondensation and defects in their silencing [START_REF] Poulet | The LINC complex contributes to heterochromatin organisation and transcriptional gene silencing in plants[END_REF]. Together, these works illustrate the complexity of the functional links between the NE, the plamina and constitutive heterochromatin that may vary depending on examined tissues e.g. the cell wall stiffness differs between meristematic and differentiated root tissues [START_REF] Somssich | Cell Wall Heterogeneity in Root Development of Arabidopsis[END_REF].

Regulation of facultative heterochromatin

Facultative LADs harbor developmentally regulated genes controlled by Polycomb complexes involved in trimethylation of histone H3 lysine 27 (H3K27me3) at the nuclear periphery. Their interaction with lamins is reported in numerous tissues to allow the regulation of gene expression via chromatin distortion resulting from NE deformation by mechanical stress conditions and/or during cellular differentiation (Bianchi et al., 2015). In human epidermal stem cells, application of long-term bi-axial stretches prevents cells from realigning to minimize strain on the nucleus and provokes the accumulation of the silencing H3K27me3 mark at epidermal differentiation genes, thus preventing epidermal stem cell differentiation [START_REF] Le | Mechanical regulation of transcription controls Polycomb-mediated gene silencing during lineage commitment[END_REF]. Thus, beyond rapid chromatin remodeling coping mechanisms dedicated to release tensions on the nucleus, long-term mechanical deformations can actually modify cell fate [START_REF] Dupont | Mechanical regulation of chromatin and transcription[END_REF].

Similar mechanisms exist in plants. In the shoot apical meristem, transcriptional repression and activation dynamically occur to specify cell fate and to promote organized cell growth and differentiation [START_REF] Nguyen | Epigenetic regulation in the shoot apical meristem[END_REF]. For example, expression of the shoot meristem maintenance homeobox gene SHOOT MERISTEMLESS (STM) is quantitatively correlated to curvature in the saddle-shaped boundary domain of the shoot apical meristem, where tissue curvature generates nuclear compression [START_REF] Landrein | Mechanical stress contributes to the expression of the STM homeobox gene in Arabidopsis shoot meristems[END_REF]. Because STM repression during organogenesis relies on the deposition of H3K27me3 by the Polycomb Repressive Complex 2 (PRC2) [START_REF] Kim | EMF1 and PRC2 cooperate to repress key regulators of Arabidopsis development[END_REF], it would be interesting to determine whether mechanical stress at the boundary helps to keep a low H3K27me3 level at STM. In any case, this example suggests a striking difference as to the functional link between mechanical stress and H3K27me3 in animals and plants. One possible explanation could originate from the limited cell-fate plasticity of the unipotent epidermal stem cells compared to the pluripotent character of plant stem cells. Another interesting finding was that defects at the nuclear periphery in Arabidopsis can lead to premature aging effects such as the presence of cell death lesions through aberrant H3K27me3 deposition. Thus, stress-related genes were found constitutively up-regulated in crwn mutants due to a decreased in H3K27me3 levels at their loci [START_REF] Choi | Loss of CRWN Nuclear Proteins Induces Cell Death and Salicylic Acid Defense Signaling[END_REF].

In animals, the mechanistic/mammalian target of rapamycin (mTOR) regulates PRC2 mediated gene silencing [START_REF] Harachi | Dual Regulation of Histone Methylation by mTOR Complexes Controls Glioblastoma Tumor Cell Growth via EZH2 and SAM[END_REF] and nuclear architecture in response to stress [START_REF] Lamm | Nuclear F-actin counteracts nuclear deformation and promotes fork repair during replication stress[END_REF]. Additionally, mTOR is also able to sense interruptions between chromatin and NE, since lamin deficiency leads to mTOR hyperactivation [START_REF] Ramos | Rapamycin reverses elevated mTORC1 signaling in lamin A/Cdeficient mice, rescues cardiac and skeletal muscle function, and extends survival[END_REF][START_REF] Chiarini | The Cutting Edge: The Role of mTOR Signaling in Laminopathies[END_REF]. In plants, TOR has been recently involved in H3K27me3 deposition and PRC2 mediated silencing of genes involved in development and stress responses [START_REF] Tang | a) PNET2 is a component of the plant nuclear lamina and is required for proper genome organization and activity[END_REF][START_REF] Ye | Glucose-driven TOR-FIE-PRC2 signalling controls plant development[END_REF]. Together with the growing proofs that TOR also controls cytoskeleton organization and dynamics [START_REF] Cao | Homeostasis of branched-chain amino acids is critical for the activity of TOR signaling in Arabidopsis[END_REF][START_REF] Dai | The TOR complex controls ATP levels to regulate actin cytoskeleton dynamics in Arabidopsis[END_REF], the position of TOR at the nexus between cytoskeleton and nuclear dynamics [START_REF] Dong | TOR represses stress responses through global regulation of H3K27 trimethylation in plants[END_REF] become increasingly evident in plant cells. Histone acetylation and trimethylation of H3K4 are typical euchromatic marks that positively correlate with gene transcription. In mouse melanoma cells, the histone deacetylases (HDAC) inhibitor trichostatin A (TSA) was used to soften stiff nuclei and alter chromatin structure in order to inhibit cell migration [START_REF] Gerlitz | Efficient cell migration requires global chromatin condensation[END_REF]. Because TSA also leads to increased tubulin acetylation and stability resulting in reduced cytoskeletal stiffness [START_REF] Fischer | Effect of Nuclear Stiffness on Cell Mechanics and Migration of Human Breast Cancer Cells[END_REF], its impact on nuclear rigidity probably reflects a combined effect on both euchromatin and cytoskeleton. Inversely, forcing animal cells (i.e., mammary epithelial cells, mesenchymal stem cells or fibroblast) into micropatterned substrates to alter cellular geometry results in smaller and stiffer nuclei, global histone deacetylation, chromatin condensation and overall reduction in gene expression [START_REF] Dupont | Mechanical regulation of chromatin and transcription[END_REF]. Besides this, a strong positive correlation was observed between nuclear volume and histone acetylation, suggesting that changes in nuclear morphology might enhance accessibility to transcriptional machinery and hence regulate total levels of transcription [START_REF] Jain | Cell geometric constraints induce modular gene-expression patterns via redistribution of HDAC3 regulated by actomyosin contractility[END_REF]. The notion that active histone marks positively respond to changes in mechanical force was further explored in melanoma aggregates at which tissue curvature promotes H3K4 methylation and H3 acetylation to increase expression of pro-oncogenic genes [START_REF] Lee | Geometric regulation of histone state directs melanoma reprogramming[END_REF]. As a possible mechanism, the cytoplasmic-to-nuclear redistribution of HDAC3 was reported to depend on actomyosin contractility [START_REF] Jain | Cell geometric constraints induce modular gene-expression patterns via redistribution of HDAC3 regulated by actomyosin contractility[END_REF]. In plants, only indirect proofs have been reported so far. On one side, nuclei change their shape during root elongation from spherical in meristem to spindle-shaped in epidermis [START_REF] Meier | Regulation of nuclear shape and size in plants[END_REF]. On the other side, using TSA to inhibit HDAC results in a hyperacetylation of histones H3 and H4 and alters the expression of specific genes involved in root cellular patterning [START_REF] Xu | Histone acetylation affects expression of cellular patterning genes in the Arabidopsis root epidermis[END_REF]. Together, nuclear shape and histone acetylation may function in mediating positional cue to direct gene patterning in the root epidermal cells.

Regulation of euchromatin

Gene positioning inside the nucleus is critical for expression [START_REF] Egecioglu | Gene positioning and expression[END_REF].

In yeast, most transcription factors are capable of tethering target gene to NPCs, thus promoting their expression [START_REF] Brickner | The Role of Transcription Factors and Nuclear Pore Proteins in Controlling the Spatial Organization of the Yeast Genome[END_REF]. Accordingly, specific NPC components are attached to chromatin loops harboring actively transcribed genes (Bianchi and Lanzuolo, 2015).

Relocation of chromatin close to NPCs for high transcriptional activity is also observed in animals, with several NPC components being responsive to mechanical signals [START_REF] Matsuda | On the nuclear pore complex and its emerging role in cellular mechanotransduction[END_REF]. This is the case for NUP210, which was recently found to promote chromatin accessibility at the nuclear periphery in response to extracellular mechanical signals during metastasis (Amin et al., 2021). In Drosophila, NUP107, a core component of the outer ring subcomplex, and NUP93, a core component of the inner ring sub-complex, were found to associate with actively transcribed genes and Polycomb-silenced regions, respectively, revealing a complex landscape of NE-genome interactions [START_REF] Gozalo | Core Components of the Nuclear Pore Bind Distinct States of Chromatin and Contribute to Polycomb Repression[END_REF]. This duality has a central role in cellular differentiation and its disequilibrium is associated with specific diseases (Bianchi and Lanzuolo, 2015).

In plants, NPCs are largely surrounded by repressive heterochromatin domains [START_REF] Barneche | Unreeling the chromatin thread: a genomic perspective on organization around the periphery of the Arabidopsis nucleus[END_REF][START_REF] Bi | Nonrandom domain organization of the Arabidopsis genome at the nuclear periphery[END_REF][START_REF] Gozalo | Core Components of the Nuclear Pore Bind Distinct States of Chromatin and Contribute to Polycomb Repression[END_REF] and some of their components can interact with heterochromatic factors such as LIKE HETEROCHROMATIN PROTEIN1 (LHP1) [START_REF] Chen | Nuclear import of LIKE HETEROCHROMATIN PROTEIN1 is redundantly mediated by importins alpha-1, alpha-2 and alpha-3[END_REF]. Reminiscent of bacterial operons, silent biosynthetic gene clusters in Arabidopsis were found at the nuclear periphery associated with heterochromatic domains, while transcriptionally active ones relocate away from the nuclear periphery [START_REF] Nutzmann | Active and repressed biosynthetic gene clusters have spatially distinct chromosome states[END_REF]. In contrast, several light-inducible loci were reported to relocate from the nuclear interior to the periphery upon their activation in response to light stress in Arabidopsis [START_REF] Feng | Light-regulated gene repositioning in Arabidopsis[END_REF]. Similarly, artificial targeting of a luciferase reporter gene to the NPC using the Lac Operator/Lac Repressor system results in its increased expression [START_REF] Smith | Marker gene tethering by nucleoporins affects gene expression in plants[END_REF].

Further supporting that NPCs act as transcriptional hubs to promote gene expression, the euchromatin binding factor GBPL3 interacts with the nuclear basket components NUP82 and NUP136, as well as with CRWN1 (Tang et al., 2022b), to coordinate expression during plant development and stress responses [START_REF] Bi | Nonrandom domain organization of the Arabidopsis genome at the nuclear periphery[END_REF]. Together, NPCs and the nuclear periphery seem to play dichotomous functions in both animal and plant cells and the question whether these functions are differently driven by mechanical forces remains to be answered.

NE dynamics and its functional relevance

Changes in nuclear structure and morphology modulate key cellular and genomic functions, thus being critical for cell differentiation and organism development [START_REF] Kalukula | Mechanics and functional consequences of nuclear deformations[END_REF]. For that reason, particular nuclear shapes were correlated to specific cell identities and/or tissue contexts in both animals and plants [START_REF] Meier | Regulation of nuclear shape and size in plants[END_REF][START_REF] Deolal | Regulation of diverse nuclear shapes: pathways working independently, together[END_REF].

Nuclear shaping during development and in response to extracellular constraints

Changes in nuclear shape usually reflect altered nuclear mechanics and are highly relevant to normal development and physiology, as well as for responses to stress and diseases in both animals and plants [START_REF] Skinner | Nuclear morphologies: their diversity and functional relevance[END_REF][START_REF] Goto | Regulation and Physiological Significance of the Nuclear Shape in Plants[END_REF]. For example, lobulated nuclei occur in the most mature form of neutrophils, making nuclei more deformable and helping neutrophils to easily pass through small gaps in endothelium and extracellular matrix [START_REF] Hoffmann | The granulocyte nucleus and lamin B receptor: avoiding the ovoid[END_REF]. Besides altered cytoskeleton organization, differentiation of bovine 1365313x, ja, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/tpj.16246 by Université De Strasbourg, Wiley Online Library on [03/05/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License and human mesenchymal stem cells implies changes in nuclear shape, stiffness and organization due to the restructuration of A/C-type lamin network and an increase in heterochromatin content. Even if these changes can be both consequences and mediators of differentiation, the nucleus seems to act as a mechanostat to modulate mechano-sensing during differentiation [START_REF] Heo | Differentiation alters stem cell nuclear architecture, mechanics, and mechano-sensitivity[END_REF]. Further supporting this, the size of nuclei was found decreased and their aspect ratio increased, while at the same time, A/C-type lamins were more expressed and redistributed toward the nuclear periphery in human mesenchymal stem cells undergoing adipocyte differentiation [START_REF] Mccolloch | Correlation between Nuclear Morphology and Adipogenic Differentiation: Application of a Combined Experimental and Computational Modeling Approach[END_REF]. Similarly, during the step-wise differentiation program that governs epidermal stratification, epidermal cells decrease their intrinsic tension and undergo marked nuclear changes with decreased nuclear volume and transcriptional activity, as well as increased heterochromatin amount and relocation toward the nuclear interior [START_REF] Miroshnikova | Epigenetic gene regulation, chromatin structure, and force-induced chromatin remodelling in epidermal development and homeostasis[END_REF]. Beside this, the nucleus can perceive tension, compression or shear from extra-cellular environment through cytoskeleton reorganization [START_REF] Kirby | Emerging views of the nucleus as a cellular mechanosensor[END_REF]. Under hypo-osmotic stress, the nucleus expands through maximal nuclear lamina stretching capacity, while under hyper-osmotic stress, the nucleoplasm contracts, and the nucleus shrinks [START_REF] Finan | The effects of osmotic stress on the structure and function of the cell nucleus[END_REF]. By expanding surface tensions at the NE, mechanical stimuli increase NPCs diameter and consequently affect all NPC related functions (Allen and Strader, 2021). Also, since ONM forms a continuum with the ER which contains MS ion channels, tensions at the NE activate these channels, leading to Ca 2+ release impacting cell contractility [START_REF] Lomakin | The nucleus acts as a ruler tailoring cell responses to spatial constraints[END_REF] and chromatin organization [START_REF] Nava | Heterochromatin-Driven Nuclear Softening Protects the Genome against Mechanical Stress-Induced Damage[END_REF].

During plant root development, besides cell shape modifications, nuclei change from rounded in the meristem to elongated in the differentiation area [START_REF] Meier | Regulation of nuclear shape and size in plants[END_REF]. Nuclear migration in Arabidopsis growing root hair (Singh et al., 2021b) or pollen tube (Zhou and Meier, 2014) is also accompanied by nuclear shape changes. In contrast to animal in which nuclei are moved by motor proteins along the MT cytoskeleton, the actin cytoskeleton and a myosin motor physically interact with the NE through a SUN-WIP-WIT bridge to enable nuclear movement in root hair [START_REF] Tamura | Myosin XI-i links the nuclear membrane to the cytoskeleton to control nuclear movement and shape in Arabidopsis[END_REF]. In addition, hyper-osmotic stress results in marked chromatin condensation [START_REF] Martins | Mechanical Regulation of Nuclear Structure and Function[END_REF]. In Arabidopsis root meristematic cells, similar changes were observed, with nuclei and heterochromatic chromocenters shrinking upon hyperosmotic stress and mechanoresponsive genes being induced (Goswami et al., 2020b). Even if knowledge is just emerging in plants, the nucleus appears to act as a mechanical rheostat during development and stress response (Goswami et al., 2020a ;[START_REF] Fal | Nuclear envelope: a new frontier in plant mechanosensing?[END_REF].

NE dynamics impacts on chromatin during cell cycle and upon DNA damage

During the transition from G1 to S/G2 phase, nuclei from proliferating human cells change their shape [START_REF] Chu | On the origin of shape fluctuations of the cell nucleus[END_REF]. Interestingly, inhibition of myosin II during G1 phase prevents nuclear flattening and impedes progression to S phase (Aureille et al., 2019). In plants, chromatin also undergoes drastic changes affecting its degree of compaction during the cell cycle [START_REF] Pecinka | Chromatin dynamics during interphase and cell division: similarities and differences between model and crop plants[END_REF]. During cell division, the NE disassembles upon entry into mitosis and reforms in telophase around the two separated sets of daughter chromosomes. In animals, a MT-induced tearing of the nuclear lamina seems to contribute to the NE breakdown [START_REF] Beaudouin | Nuclear envelope breakdown proceeds by microtubule-induced tearing of the lamina[END_REF]. Then, upon mitosis exit, the NE reassembles around decondensed chromosomes through the binding of INM proteins to chromatin [START_REF] Ulbert | Direct membrane protein-DNA interactions required early in nuclear envelope assembly[END_REF]. In plants, NE breakdown is also dictated by MT dynamics with the relocation of the nucleoporin RAE1 on spindle MTs [START_REF] Masoud | Microtubule nucleation and establishment of the mitotic spindle in vascular plant cells[END_REF]. In mammalian cells, SUN1 and a membrane-associated histone acetyltransferase hALP contribute to chromosome decondensation at the end of mitosis during NE reformation [START_REF] Chi | Histone acetyltransferase hALP and nuclear membrane protein hsSUN1 function in decondensation of mitotic chromosomes[END_REF]. Following NE dynamics, Arabidopsis SUN1 orthologs changed their localization dynamically during mitosis [START_REF] Oda | Dynamics of Arabidopsis SUN proteins during mitosis and their involvement in nuclear shaping[END_REF].

However, the underlying mechanisms of NE reformation are not yet understood.

In human cancer cells, mechanical forces can increase DNA replication stress and genome instability thereby contributing to tumorigenesis. Indeed, nuclear deformations resulting from cell migration in tight spaces or external cell compression were found to cause DNA damage associated with replication stress without NE rupture [START_REF] Shah | Nuclear Deformation Causes DNA Damage by Increasing Replication Stress[END_REF]. One explanation could be that torsional stress in DNA increases due to physical deformations of the nucleus. This explanation is supported by the fact that the ataxia telangiectasia mutated and Rad3 related (ATR) protein, which is an upstream regulator of replicative stress, has been reported to be mechanosensitive [START_REF] Kumar | ATR mediates a checkpoint at the nuclear envelope in response to mechanical stress[END_REF]. ATR-defective cells exhibit altered nuclear morphology and mechanical properties, together with an aberrant perinuclear chromatin organization and an increased heterochromatinization [START_REF] Kidiyoor | ATR is essential for preservation of cell mechanics and nuclear integrity during interstitial migration[END_REF]. In Arabidopsis, crwn1crwn4 double mutants are hyper sensitive to genotoxic stress and show reduced anchoring of RAD54 at the nuclear periphery [START_REF] Hirakawa | Characterization of DNA Repair Foci in Root Cells of Arabidopsis in Response to DNA Damage[END_REF]. Similarly, gip1gip2 mutants present an increased genome instability due to the impaired recruitment of RAD51 at double strand DNA breaks at the nuclear periphery of root meristematic nuclei (Singh et al., 2021a). Therefore, the NE in eukaryotes contributes to homologous recombination repair and genome stability at the nuclear periphery. Up to now most of nuclear and cytoplasmic membrane shape changes were evaluated through morphological and physical parameters using technical approaches such as microrheometry, Atomic Force Microscopy (AFM) or optical tweezers (Goswami et al., 2020a). In order to quantify and visualize intracellular membrane tensions in cellulo, new tools have to be developed. In animals, the Fluorescent Lipid Tension Reporter (FliptR) can measure external membrane tensions based on lifetime measurements [START_REF] Colom | A fluorescent membrane tension probe[END_REF]. More recently, the development of a HaloTag-Nuclear Localization Signal photocleavable fluorescent probe to evaluate tensions in the NE seems very promising [START_REF] Lopez-Andarias | Photocleavable Fluorescent Membrane Tension Probes: Fast Release with Spatiotemporal Control in Inner Leaflets of Plasma Membrane, Nuclear Envelope, and Secretory Pathway[END_REF]. In plants, recent development of an imaging microviscosity toolbox for cells and tissues has enabled to specifically visualize tensions at the plasma membrane and cell wall [START_REF] Michels | Complete microviscosity maps of living plant cells and tissues with a toolbox of targeting mechanoprobes[END_REF].

Förster Resonance Energy Transfer (FRET) protein bioSensors of osmotic stress such as SENSOR EXPRESSING DISORDERED PROTEIN 1 (SED1), based on the Arabidopsis intrinsically disordered AtLEA4-5 protein, has already been developed and used to track the effects of osmotic stress on living bacteria, plant and human cells [START_REF] Cuevas-Velazquez | Intrinsically disordered protein biosensor tracks the physical-chemical effects of osmotic stress on cells[END_REF]. Non-destructive and non-invasive methods such as the new type of optical elastography named Brillouin microscopy, based on photon-phonon interactions, can be used to evaluate cellular and tissue mechanical properties in 3D [START_REF] Prevedel | Brillouin microscopy: an emerging tool for mechanobiology[END_REF] and also intra-nuclear mechanics [START_REF] Liu | Changes in intra-nuclear mechanics in response to DNA damaging agents revealed by time-domain Brillouin microspectroscopy[END_REF]. Live cell imaging of macromolecular crowding will bring as well new information about changes of cell physical properties in response to mechanical cues.

Recently, the development of genetically encoded multimeric nanoparticles (GEMs) as microrheology probes has allowed to evaluate biophysical properties of the cytoplasm and nucleoplasm of yeast and human cells [START_REF] Delarue | mTORC1 Controls Phase Separation and the Biophysical Properties of the Cytoplasm by Tuning Crowding[END_REF]. At the chromatin level, live-cell imaging has to be addressed in different genetic backgrounds by modifying epigenetic status through directed global and local histone modifications using chromatybodies and Cas9 approaches (Fal et al., 2021b).

Altogether, current and future technical improvements will contribute to further address and unravel mechanobiology processes in the very particular context of walled plant cells.

These recent technology developments will also allow to investigate in more detail reciprocal interplays between chromatin, nucleoskeleton, NE and cytoskeleton impacting nuclear mechanics in the context of plant growth and development. Lastly, considering mechanical stress acclimation/adaptation of plants, the expected new findings will certainly contribute to understand how a mechanical stress may confer transcriptional memory and promote plant defense priming to (eventually) respond more efficiently to other abiotic and biotic stresses [START_REF] Brenya | Mechanical stress acclimation in plants: Linking hormones and somatic memory to thigmomorphogenesis[END_REF].

Figure Legends:

Figure 1: Mechanical connection from the plasma membrane to the NE in animal mesenchymal cells and differentiated plant cells. In both cell types, MFs (in red) are connected to protein complexes at the plasma membrane complexes: to focal adhesions allowing cell-matrix connection in animals, and to plasmodesmata allowing cell-cell communication in plants. The other extremities of MFs are connected to the NE via LINC complexes. A particularity of the animal cell, in comparison to plants, is the presence of elongated membrane structures called lamellipodia which allow cell movement along the surrounding matrix and are formed by the polymerisation of MFs pushing against the plasma membrane. Another animal specificity is the presence of IFs (in blue) establishing connections with hemidesmosomes and LINC complexes. MTs (in green) are nucleated from γTuRCs at the centrosome in animal cells and plus-ends connect either to the plasma membrane through crosslinks with actin and IFs, or to the NE with LINC complexes. In acentrosomal plant cells, endoplasmic MTs nucleate from both the plasma membrane and the NE. Cortical MTs (here indicated in pale green in the cell background) guide the movement of cellulose synthase complexes (not shown) and align perpendicularly to the direction of cell elongation. Cortical MTs reorient during mechanical stress to follow the direction of the strain. Characterized mechanosensory receptors are indicated in both models (FER, Piezo). Mitochondria (red), chloroplasts (green) and the vacuole (orange) are also represented. Nuclear structures are detailed in Figure 2. Cytoskeleton attachment to the NE differs significantly between animals and plants. While MTs can bind to Nesprin4 specific LINC complexes via kinesin in animal cells (A), the only way reported so far in plants for their interaction to the NE is through γ-TuRC and associated GIP1/2 proteins present at the ONM (H). The γ-TuRC positioning may involve a possible TSA1/trans-NE complex which is yet to be fully described. GIP1/2 are also found at the INM associated to the centromere (CENH3). MFs bind through the LINC complexes in both models but the attachment differs significantly at the ONM: while Nesprin1/2 is used in animal cells (D), different KASH proteins are used in plants (F), namely the WIP1/2/3 and WIT1/2. It is interesting to highlight that WIP1/2/3 interact with SUN1/2 proteins, WIT1/2 do not. The stabilisation of the interaction with MFs via Myosin XI-i also involves two additional proteins, namely WPP and RanGAP. Other KASH proteins such as SINE1/2 can bind to MFs and were shown to also be necessary for MT patterning, but in a way not yet determined (G). Additional KASH proteins in animals such as Nesprin-3 can bind Vimentin-based IFs (C) while IFs are absent in plants. Other KASH proteins (TIK, SUN3/4) have been identified as interacting with SUN complexes in plants, but their function still remains unclear. The cytoskeleton network allows the mechanical propagation of tensile and shearing forces from the cellular periphery to the NE, resulting in its mechanical deformation, but this deformation can also result from the induced condensation/decondensation of the chromatin from the inside of the nucleus. Chromatin (pale blue) tethering to the nuclear periphery has been observed in both models and requires the presence of lamins (A/C and B-type lamins) in animal cells and lamin-like proteins (CRWN1/4, KAKU4) in plants. Both lamins and lamin-like proteins bind to the SUN complexes (highly conserved between both reigns) with the addition of lamin-associated proteins which are specific to animals (Emerin, Man1, Nur1, Lem2) and plants (PNET2) (B, H). At INM, NEAP1/2/3 interact with the TF bZIP18 (E). Some lamin and lamin-like proteins can also be found attached to the chromatin in the nucleoplasm, especially A/C and B lamins in animals and CRWN2/3 in plants. The chromatin tethered to the nuclear periphery is highly enriched in heterochromatin and repressing complexes such as PRC2 which maintain transcriptional repression through the deposition of H3K27me3 epigenetic marks. The nucleoplasm apart from the nucleolus is on the contrary mostly composed of euchromatin. Compared to the rest of the nuclear periphery, euchromatin is highly enriched at the NPCs to promote gene expression, involving the nuclear pore basket components NUP2 and NUP160 in animals (A), and the basket proteins NUP82, NUP1/NUP136 and the ring protein CPR5 in plants (G). Other proteins of the basket were shown to be necessary for heterochromatin organisation (i.e., TPR, NUP153 and NUP210 in animals, NUP1/NUP136 in plants), or for the regulation of chromatin attachment to the NPC (NUP155, NUP93 and NUP62 in animals). Other proteins such as NUP107 were shown to be more specifically involved in the activation of DNA replication. NPCs are also important for the shuttling of mechanoresponsive factors through the NE. In animals, TOR is mechanically activated through Piezo1-related Ca 2+ signalling from the ER and actively regulates gene expression (B). In plants, it is activated by FER and phosphorylates the PRC2 component FIE, resulting in FIE shuttling through the NPC for the regulation of gene expression (E). Interestingly, we can highlight that TOR seems to regulate dynamics of the cytoskeleton in a reign-specific way: while it was shown to regulate MT formation in animals, it appears to rather regulate the formation of MFs in plants. Finally, other proteins have been shown in animals to shuttle through the NPC as a response to tensile stress on the NE: G-actin for instance, which can be used as a transcription factor, is exported outside of the nucleus to help the polymerisation of a perinuclear ring of F-actin preventing NE rupture (D). YAP/TAZ

  domain, the N-terminal cytoplasmic part of the KASH proteins is also highly diverse, as are the functions of KASH proteins. In animals and plants, interactions between various KASH proteins and SUN1/2 proteins in the lumen of the NE constitute physical bridges at the nucleocytoplasmic interface and allow the formation of various LINC complexes mediating differential associations between cytoskeleton and nucleoskeleton. In animals, the LINC complexes interact directly with the MFs through the N-terminal actin-binding domain of KASH proteins such as the two vertebrate paralogues Nesprin1

  Outlook: A need to develop tools for live cell imaging linking nuclear mechanics and chromatin remodeling

  1365313x, ja, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/tpj.16246 by Université De Strasbourg, Wiley Online Library on [03/05/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License

Figure 2 :

 2 Figure 2: Protein complexes and functional modules involved in the organisation and dynamics of the NE in animal (left) and plant cells (right).Cytoskeleton attachment to the NE differs significantly between animals and plants. While MTs can bind to Nesprin4 specific LINC complexes via kinesin in animal cells (A), the only way reported so far in plants for their interaction to the NE is through γ-TuRC and associated GIP1/2 proteins present at the ONM (H). The γ-TuRC positioning may involve a possible TSA1/trans-NE complex which is yet to be fully described. GIP1/2 are also found at the INM associated to the centromere (CENH3). MFs bind through the LINC complexes in both models but the attachment differs significantly at the ONM: while Nesprin1/2 is used in animal cells (D), different KASH proteins are used in plants (F), namely the WIP1/2/3 and WIT1/2. It is interesting to highlight that WIP1/2/3 interact with SUN1/2 proteins, WIT1/2 do not. The stabilisation of the interaction with MFs via Myosin XI-i also involves two additional proteins, namely WPP and RanGAP. Other KASH proteins such as SINE1/2 can bind to MFs and were shown to also be necessary for MT patterning, but in a way not yet determined (G). Additional KASH proteins in animals such as Nesprin-3 can bind Vimentin-based IFs (C) while IFs are absent in plants. Other KASH proteins (TIK, SUN3/4) have been identified as interacting with SUN complexes in plants, but their function still remains unclear. The cytoskeleton network allows the mechanical propagation of tensile and shearing forces from the cellular periphery to the NE, resulting in its mechanical deformation, but this deformation can also result from the induced condensation/decondensation of the chromatin from the inside of the nucleus. Chromatin (pale blue) tethering to the nuclear periphery has been observed in both models and requires the presence of lamins (A/C and B-type lamins) in animal cells and lamin-like proteins (CRWN1/4, KAKU4) in plants. Both lamins and lamin-like proteins bind to the SUN complexes (highly conserved between both reigns) with the addition of lamin-associated proteins which are specific to animals (Emerin, Man1, Nur1, Lem2) and plants (PNET2) (B, H). At INM, NEAP1/2/3 interact with the TF bZIP18 (E). Some lamin and lamin-like proteins can also be found attached to the chromatin in the nucleoplasm, especially A/C and B lamins in animals and CRWN2/3 in plants. The chromatin tethered to the nuclear periphery is highly enriched in heterochromatin and repressing complexes such as PRC2 which maintain transcriptional repression through the deposition of H3K27me3 epigenetic marks. The nucleoplasm apart from the nucleolus is on the contrary mostly composed of euchromatin. Compared to the rest of the nuclear periphery, euchromatin is highly enriched at the NPCs to promote gene expression, involving the nuclear pore basket components NUP2 and NUP160 in animals (A), and the basket proteins NUP82, NUP1/NUP136 and the ring protein CPR5 in plants (G). Other proteins of the basket were shown to be necessary for heterochromatin organisation (i.e., TPR, NUP153 and NUP210 in animals, NUP1/NUP136 in plants), or for the regulation of chromatin attachment to the NPC (NUP155, NUP93 and NUP62 in animals). Other proteins such as NUP107 were shown to be more specifically involved in the activation of DNA replication. NPCs are also important for the shuttling of mechanoresponsive factors through the NE. In animals, TOR is mechanically activated through Piezo1-related Ca 2+ signalling from the ER and actively regulates gene expression (B). In plants, it is activated by FER and phosphorylates the PRC2 component FIE, resulting in FIE shuttling through the NPC for the regulation of gene expression (E). Interestingly, we can highlight that TOR seems to regulate dynamics of the cytoskeleton in a reign-specific way: while it was shown to regulate MT formation in animals, it appears to rather regulate the formation of MFs in plants. Finally, other proteins have been shown in animals to shuttle through the NPC as a response to tensile stress on the NE: G-actin for instance, which can be used as a transcription factor, is exported outside of the nucleus to help the polymerisation of a perinuclear ring of F-actin preventing NE rupture (D). YAP/TAZ

  1365313x, ja, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/tpj.16246 by Université De Strasbourg, Wiley Online Library on [03/05/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License

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Funding

This work was supported by the Centre National de la Recherche Scientifique (CNRS), by HFSP grant RGP 0009/2018, ANR-18-CE20-0011project REWIRE and ANR-20-CE13-0025

is another mechanoresponsive transcription factor which necessitates F-actin connection at LINC complexes to be transferred through the NPC for the regulation of stress responsive genes. The question marks indicate the absence of knowledge for the interactors.

Table 1: NE components and their involvement in mechanosensing.

Supplementary S1-List of related publications to Table 1 Table 1 : NE components and their involvement in mechanosensing. Zhou et al., 2014;[START_REF] Groves | Recent advances in understanding the biological roles of the plant nuclear envelope[END_REF][START_REF] Groves | Recent advances in understanding the biological roles of the plant nuclear envelope[END_REF][START_REF] Groves | Recent advances in understanding the biological roles of the plant nuclear envelope[END_REF] [START_REF] Janski | The GCP3-interacting proteins GIP1 and GIP2 are required for γ-tubulin complex protein localization, spindle integrity, and chromosomal stability[END_REF]Nakamura et al., 2012;Batzenschalger et al., 2013;Batzenschalger et al. 2015;Goswami et al., 2020b GIP2 Regulates NPC distribution around the NE. Necessary for MT nucleation on the NE. Interaction with centromeres.Controls centromeric cohesion, nuclear size and expression of touch responsive genes. [START_REF] Janski | The GCP3-interacting proteins GIP1 and GIP2 are required for γ-tubulin complex protein localization, spindle integrity, and chromosomal stability[END_REF]Nakamura et al., 2012;Batzenschalger et al., 2013;Batzenschalger et al. 2015 ;Goswami et al., 2020b Linker of Nucleoskeleton and Cytoskeleton (LINC) Complex