# The role of post-translational modifications in the dynamics of cytoplasmic biomolecular condensates in plants

Margaux Legoux, Jean-philippe Reichheld, Rémy Merret

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Margaux Legoux, Jean-philippe Reichheld, Rémy Merret. The role of post-translational modifications in the dynamics of cytoplasmic biomolecular condensates in plants. New Phytologist, 2025, 10.1111/nph.70593. hal-05290294

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Research review

# The role of post-translational modifications in the dynamics of cytoplasmic biomolecular condensates in plants

Authors for correspondence:
*Jean-Philippe Reichheld*
Email: jpr@univ-perp.fr

Rémy Merret
Email: remy.merret@cnrs.fr

Received: 24 July 2025
Accepted: 10 September 2025

**Margaux Legoux**¹,² ID, **Jean-Philippe Reichheld**¹,² ID and **Rémy Merret**³ ID

¹CNRS-LGDP UMR 5096, 58 Avenue Paul Alduy, 66860, Perpignan, France; ²Université de Perpignan Via Domitia, LGDP-UMR5096, 58 Avenue Paul Alduy, 66860, Perpignan, France; ³IBMP UPR 2357, 23 rue Général Zimmer, 67000, Strasbourg, France

New Phytologist (2025)
doi: 10.1111/nph.70593

**Key words:** cytoplasmic biomolecular condensates, granules, liquid-liquid phase separation, post-translational modifications, stress.

## Summary

Cytoplasmic biomolecular condensates are membrane-less structures important for cell homeostasis, especially during stress conditions. These aggregates concentrate RNA, protein, and metabolites during a wide variety of stresses. The formation of cytoplasmic biomolecular condensates was studied extensively in plants, revealing many key actors involved in their nucleation. More recently, post-translational modifications (PTMs) of some of these components appear as a novel layer in cytoplasmic biomolecular condensate formation. Here, we describe the importance of the PTMs in cytoplasmic biomolecular condensate dynamics in plants. We highlight the major contribution of phosphorylation and ubiquitination in these processes and discuss the involvement of other recently discovered PTMs.

## Introduction

Environmental stresses, such as temperature fluctuations, drought, salt, and oxidative stress, trigger a wide range of physiological and molecular changes in all living organisms. Like other organisms, plants have evolved complex and highly regulated responses to cope with these environmental challenges. One critical aspect of the cellular stress response involves the protection and regulation of essential macromolecules, including DNA, RNA, and proteins. Among these, the regulation of messenger RNA (mRNA) metabolism has emerged as a particularly dynamic and responsive layer of gene expression control (Xiang & Dong, 2025). This regulation allows plants to swiftly adapt their proteome in response to changing environmental conditions by modulating mRNA translation, stability, and localization.

In eukaryotic cells, untranslated or translationally repressed mRNAs often aggregate with RNA-binding proteins and other associated factors to form cytoplasmic structures known as messenger ribonucleoprotein (mRNP) granules. These dynamic assemblies, also referred to as biomolecular condensates, represent membrane-less organelles that compartmentalize biochemical reactions and modulate gene expression in response to cellular needs (Banani et al., 2017). The term 'biomolecular

condensates' broadly encompasses various condensate types that form via a biophysical process called liquid-liquid phase separation (LLPS), enabling the selective concentration of specific molecules within discrete cellular domains. Recent research has highlighted the central role of biomolecular condensates in plant stress responses (Solis-Miranda et al., 2023). In particular, cytoplasmic biomolecular condensates such as processing bodies (PBs), stress granules (SGs), and siRNA-bodies have been implicated in diverse aspects of plant development and stress adaptation (Field et al., 2023). These structures serve not only as sites of mRNA storage, degradation, or translational control but also as dynamic regulators that help to buffer the cellular effects of stress.

A major breakthrough in our understanding of biomolecular condensate biology has been the discovery that their assembly and disassembly are tightly regulated by post-translational modifications (PTMs) of key protein components (Kearly et al., 2024). PTMs such as phosphorylation, ubiquitination, acetylation, and SUMOylation can modulate the physicochemical properties of proteins, influencing their solubility, interaction networks, subcellular localization, and activity. These reversible modifications provide a rapid and reversible mechanism for cells to remodel condensate composition and dynamics in response to external cues.
In the context of environmental stress, PTMs represent a powerful means by which plants can fine-tune condensate behavior and, by extension, mRNA metabolism and metabolic processes. These modifications can alter the biochemical properties of proteins, their localization, activity, or interaction with other macromolecules (Vu et al., 2018).

In this review, we aim to synthesize recent advances in our understanding of how PTMs regulate the formation, composition, and function of cytoplasmic biomolecular condensates in plants. We will explore the molecular mechanisms through which PTMs influence condensate dynamics, highlight emerging examples of stress-responsive PTM-mediated regulation, and discuss the broader implications of this regulation for plant stress tolerance and resilience.

## Techniques used to characterize cytoplasmic biomolecular condensate composition

In recent years, significant progress has been made in developing robust techniques to characterize the molecular composition of cytoplasmic biomolecular condensates. In plants, initial insights were gained through mass spectrometry analyses of interactors associated with core granule components. These studies utilized transgenic lines combined with immunoprecipitation approaches (Gutierrez-Beltran et al., 2015, 2021; Lokdarshi et al., 2016). As an example, Tudor Staphylococcal Nuclease 2 (TSN2) was used as an SG marker and allows the identification of 148 stress-dependent interactors potentially interacting in SG (Gutierrez-Beltran et al., 2021). To improve the specificity and enrichment of granule-associated proteins, some studies integrated immunoprecipitation with granule purification techniques based on differential centrifugation (Kosmacz et al., 2019; Li et al., 2024; Wang et al., 2024; Xie et al., 2024; Q. Chen et al., 2024). More recently, proximity labeling methods based on TurboID have been employed as a powerful alternative for capturing the dynamic and spatially restricted proteomes of cytoplasmic condensates (Liu et al., 2023, 2024). Collectively, these approaches extend the large diversity of proteins identified in cytoplasmic condensates (reviewed in (Solis-Miranda et al., 2023)). Intriguingly, tens of proteins not directly linked to RNA biology have also been consistently identified, suggesting broader cellular functions for these condensates.

Beyond proteins, diverse small molecules have been found within cytoplasmic condensates. These include phospholipids, polar metabolites such as amino acids and nucleotides (Kosmacz et al., 2018, 2019; Chodasiewicz et al., 2022; Song et al., 2024). While not localized in condensates, some metabolites were also proposed to participate in condensate formation and dynamics. 2',3'-cAMP has been proposed to play roles in SG formation and PB dynamics (Kosmacz et al., 2018, 2019; Chodasiewicz et al., 2022). Additionally, energy-related molecules such as ATP and NAD⁺ have been shown to influence protein condensation behavior, possibly acting as modulators of phase separation (Song et al., 2024). More precisely, the formation of TIR condensates (N-terminal Toll/interleukin-1 receptor) is mediated by ATP and NAD⁺. The direct binding of ATP and

NAD⁺ to TIR domain protein is sufficient to induce condensation *in vitro* (Song et al., 2024). Enzymatic components are also prevalent in these condensates. For example, enzymes involved in protein dephosphorylation/phosphorylation (such as MAP kinases), ethylene pathway (such as ACC oxidase), glutathione pathway (such as glutathione peroxidase), or glycolysis (such as enolase) were identified in SGs or PBs (Solis-Miranda et al., 2023), highlighting the potential importance of catalytic processes in condensate assembly and function. In the following sections, we will explore how PTMs contribute to the regulation of cytoplasmic biomolecular condensate dynamics (Fig. 1; Table 1). Our survey reveals that PTMs of both RNA-binding and non-RNA-binding proteins contribute to condensate dynamics in plants.

## Phosphorylation-mediated dynamics of cytoplasmic biomolecular condensates

Recent studies have identified several enzymes involved in phosphorylation and dephosphorylation within cytoplasmic biomolecular condensates, such as SG and PB (Lokdarshi et al., 2016; Kosmacz et al., 2019; Gutierrez-Beltran et al., 2021; Solis-Miranda et al., 2023; Yuan & Zhao, 2025) (Fig. 1a,b; Table 1a). A key example involves SnF1-Related protein kinases 1 and 2 (SnRK1 and SnRK2), central components of stress signaling pathways in plants. Both kinases have been detected in distinct condensates – SnRK1 localizing predominantly to SGs and SnRK2 to PBs in *Arabidopsis thaliana* (Gutierrez-Beltran et al., 2021; Yuan & Zhao, 2025) (Fig. 1a,b). Under heat stress, the TSN1 and 2 physically interact with SnRK1 to facilitate its condensation and activation within SGs (Fig. 1a). Notably, heat-induced phosphorylation of SnRK1α at threonine 175 is abolished in a *tsn1 tsn2* double mutant, which also shows a marked reduction in SnRK1 accumulation in SGs. This finding underscores the critical role of SG-mediated kinase localization in plant stress signaling. SnRK2 proteins, on the other hand, were recently proposed as a molecular crowding sensor. Under normal conditions, SnRK2s are associated with ABI1, their negative regulator ABA-insensitive 1, to prevent activation of a stress response. Upon stress exposure, SnRK2s form condensates that enable their dissociation from ABI1, leading to activation of a stress response and subsequent initiation of stress signaling (Yuan & Zhao, 2025) (Fig. 1b). Moreover, SnRK2s' activity is also modulated by B4 Raf-like protein kinases, which localize to PBs during stress (Lin et al., 2020; Soma et al., 2020). This activation by segregation allows the regulation of stress-responsive genes under severe osmotic stress. In fact, *snrk2* mutants exhibit growth defects under osmotic stresses, more particularly during seed germination (Yuan & Zhao, 2025). These findings mirror observations in mammalian systems, where condensation of kinases and phosphatases is a well-established stress response mechanism (Su et al., 2016; Watanabe et al., 2021). This suggests that condensation-mediated control of kinase/phosphatase activity may be a conserved and universal strategy across kingdoms.

Beyond signaling proteins, phosphorylation has also been implicated in regulating the assembly, dynamics, and size of
<figure><img src="image_3.png" /><figcaption>**Fig. 1** Impact of post-translational modifications on cytoplasmic biomolecular condensate dynamics. The figure shows the importance of phosphorylation (a–g), ubiquitination (h, i), and other PTMs (j–m) in the dynamics of cytoplasmic biomolecular condensate formation under different biotic and abiotic stresses and for different target proteins. Phosphorylation can lead to the formation or coalescence of stress granules (a). Mutations in specific phosphosites can lead to opposite effects such as stress granule reduction or stress granule coalescence (c). Phosphorylation can also lead to condensate formation by liquid–liquid phase separation (b, g). Phosphorylation can induce the accumulation of target proteins in processing bodies (f) or, conversely, lead to the reduction or disassembly of processing bodies (d, e). Ubiquitination appears to play a positive role in the formation of stress granules since, under stress conditions, many target proteins are ubiquitinated, leading to their accumulation in stress granules (h, i). The proteasome is also present in stress granules (h). Other modifications, such as deacetylation of certain proteins, lead to their accumulation in stress granules (j); modification of the redox state of specific cysteines and potentially SUMOylation are also involved in condensate formation via liquid–liquid phase separation (k–m). flg22, Flagellin peptide flg22; H₂O₂, hydrogen peroxide; KEG, KEEP-ON-GOING; LLPS, liquid–liquid phase separation; MPK3/6, Mitogen-activated protein kinases 3 and 6; PB, processing bodies; SA, Salicylic acid; SG, stress granules. This figure was created in BioRender. Legoux, M. (2025) https://BioRender.com/4e9tkk4.</figcaption></figure>

biomolecular condensates through modifications of RNA-binding proteins (Fig. 1c–g; Table 1a). For instance, phosphorylation of tandem CCCH zinc Finger proteins by MAP kinases MPK3 and MPK6 modulates their behavior in condensates (Tabassum *et al.*, 2020; He *et al.*, 2024). In the case of TZF1, specific phosphorylation at serines 71, 73, and 80 is triggered by treatment with the flagellin peptide flg22 of *Pseudomonas syringae*. Mutating these sites leads to aberrant SG fusion and oversized condensates (Fig. 1c), linking phosphorylation to condensate size homeostasis. Similarly, TZF9 undergoes multi-site phosphorylation by MPK3/6 following flg22 perception, reducing its localization to PB and SG (Tabassum *et al.*, 2020) (Fig. 1d). As TZF9 interacts with the poly(A)-Binding protein 2 (PAB2) localized in SG during stress, it was proposed that its phosphorylation contributes to the

translational control of defense mRNAs, while direct evidence is missing (Tabassum *et al.*, 2020). This phosphorylation regulatory mechanism appears to extend to RNA decay factors. For example, flg22, known to elicit a specific innate immune response, induces phosphorylation of decapping protein 1 (DCP1) at serine 237, which is required for PB disassembly (Yu *et al.*, 2019) (Fig. 1e). DCP1 phosphorylation was proposed to trigger mRNA decay involved in biotic stress responses. Conversely, flg22-dependent phosphorylation of the mRNA decay factor protein associated with topoisomerase II (PAT1) by the MAP kinase (MPK4) promotes its recruitment to PBs (Roux *et al.*, 2015) (Fig. 1f). These latter examples highlight that flg22 induces phosphorylation of multiple substrate proteins to enhance or suppress their association with condensates (Fig. 1c–f). Therefore, phosphorylation might
<table><caption>**Table 1** Summary of the different post-translational modifications implicated in condensate dynamics in plants: (a) Phosphorylation; (b) ubiquitination; (c) acetylation; (d) redox regulation.</caption><thead><tr><th>Protein</th><th>Fonction</th><th>Impacts</th><th>Condensates</th><th>Stress</th><th>References</th></tr></thead><tbody><tr><td colspan="6"><strong>(a) Phosphorylation</strong></td></tr><tr><td>SnRK1</td><td>Kinase</td><td>TSN interacts with SnRK1 and enhances its kinase activity, the phosphorylation of SnRK1 mediates its assembly in SG.</td><td>Stress Granules</td><td>Heat</td><td>Gutierrez-Beltran et al. (2021)</td></tr><tr><td>SnRK2</td><td>Kinase</td><td>SnRK2 dissociates from the negative regulator ABI1 by the formation of condensates which conduce to its activation. This activation can be modulated by a protein kinase which localizes into PB during stress.</td><td>Crowding condensates</td><td>Osmotic</td><td>Yuan & Zhao (2025)</td></tr><tr><td>TZF1</td><td>RBP</td><td>Phosphorylation of TZF1 via MPK3 and 6 regulates the dynamics of SG formation.</td><td>Stress Granules</td><td>Biotic</td><td>He et al. (2024)</td></tr><tr><td>TZF9</td><td>RBP</td><td>Phosphorylation of TZF9 via MKP3 and MPK6 leads to reduction of PB and RNA-binding properties.</td><td>Processing bodies</td><td>Biotic</td><td>Tabassum et al. (2020)</td></tr><tr><td>DCP1</td><td>RBP</td><td>DCP1 phosphorylation at serine 237 via MPK3 and PK6 is required for PB disassembly.</td><td>Processing bodies</td><td>Biotic</td><td>Yu et al. (2019)</td></tr><tr><td>PAT1</td><td>RBP</td><td>Phosphorylation of PAT1 via MPK4 induces its localization into PB.</td><td>Processing bodies</td><td>Biotic</td><td>Roux et al. (2015)</td></tr><tr><td>GRP7</td><td>RBP</td><td>GPR7 phosphorylation by FERONIA leads to LLPS separation and is link to heat stress tolerance. GRP7 recruits mRNAs and translation machinery which is essential for SG formation.</td><td>LLPS</td><td>Heat</td><td>Xu et al. (2024)</td></tr><tr><td colspan="6"><strong>(b) Ubiquitination</strong></td></tr><tr><td>Proteasome constituents</td><td>Proteasome</td><td>Ubiquitination is needed for SG disassembly.</td><td>Stress granules</td><td>Heat</td><td>Xie et al. (2024)</td></tr><tr><td>HSP101</td><td>Chaperone</td><td>HSP101 and the proteasome are involved in the solubilization and degradation of ubiquitylated proteins during recovery after stress, needed for plant survival to proteotoxic stress.</td><td>Stress granules</td><td>Heat</td><td>McLoughlin et al. (2019)</td></tr><tr><td>AP-3β</td><td>Trafficking</td><td>The 19S regulatory particle is recruited to facilitate SG disassembly.</td><td>Stress granules</td><td>Heat</td><td>Pang et al. (2025)</td></tr><tr><td>Autophagy proteins</td><td>Autophagy</td><td>After heat stress, the disassembly of SG allows autophagy proteins to relocate in the cytoplasm, enabling fast elimination of ubiquitinated aggregates. In SG-deficient mutant, this activation is delayed leading to inefficient removal of ubiquitinated proteins.</td><td>Stress granules</td><td>Heat</td><td>Li et al. (2024)</td></tr><tr><td>TZF1</td><td>RBP</td><td>TZF1 is ubiquitinated inducing its accumulation to SG. Mutation of TZF1 ubiquitination sites affect SG assembly.</td><td>Stress granules</td><td>Biotic</td><td>He et al. (2024)</td></tr><tr><td colspan="6"><strong>(c) Acetylation</strong></td></tr><tr><td>HDA714</td><td>Histone deacetylase</td><td>HDA714 deacetylates some SG proteins influencing their aggregation.</td><td>Stress granules</td><td>Heat</td><td>Q. Chen et al. (2024), Z. Chen et al. (2024)</td></tr><tr><td colspan="6"><strong>(d) Redox regulation</strong></td></tr><tr><td>TMF</td><td>Transcription factor</td><td>The production of hydrogen peroxide leads to liquid –liquid phase separation of TMF in tomato meristem.</td><td>Nuclear LLPS</td><td>Oxidative</td><td>Huang et al. (2021)</td></tr><tr><td>NPR1</td><td>Signaling</td><td>NPR1 cysteines in or nearby IDR regions leads to the formation of condensates.</td><td>Condensates</td><td>Biotic</td><td>Zavaliev et al. (2020)</td></tr></tbody></table>

ABI1, ABA-insensitive 1; AP-3β, β subunit of adaptor protein –3 complex; DCP1, decapping protein 1; GRP7, glycine-rich protein 7; HSP101, heat shock protein 101; HDA714, histone deacetylase 714; LLPS, liquid–liquid phase separation; MPK3, mitogen-activated protein kinase 3; MPK6, mitogen-activated protein kinase 6; NPR1, non-expresser of pathogenesis related PR1; PAT1, protein associated with topoisomerase II; PB, processing-bodies; RBP, RNA-binding protein; SnRK1, Sucrose nonfermenting 1-related protein kinase 1; SnRK2, Sucrose nonfermenting 1-related protein kinase 2; SG, Stress Granule; TMF, Terminating Flower; TZF1, tandem CCCH zinc finger 1; TZF9, tandem CCCH zinc finger 9.

constitute a way to modify the composition of PB under stress conditions.

Heat stress also modulates phase separation through phosphorylation. The Glycine-Rich RNA-binding protein GRP7 is phosphorylated in response to elevated temperatures, promoting its condensation in Arabidopsis (Xu *et al.*, 2024) (Fig. 1g). Notably, natural variations in GRP7 phosphosites influence its condensation

behavior and correlate with temperature adaptation, implying that GRP7 phase separation plays a vital role in thermotolerance. GRP7 phosphorylation appears essential to the formation of SG to recruit mRNA and the translation machinery components to inhibit translation upon heat stress (Xu *et al.*, 2024). Furthermore, emerging evidence suggests that light signaling can also impact phosphorylation-dependent condensation, particularly within the
nucleus (Feng et al., 2024), expanding the role of PTM to nuclear condensates. In mammals, phosphorylation plays a dual role in condensate formation, particularly in the assembly of SGs, depending on the specific target protein. For instance, Ras GTPase-activating protein-binding protein 1 (G3BP1), a key factor in SG nucleation, can be phosphorylated at serine 149 by Casein Kinase 2, leading to a reduction in SG formation (Reineke et al., 2017). Conversely, phosphorylation can also promote SG assembly; for example, phosphorylation of eukaryotic Initiation Factor 2α (eIF2α) by specific stress-activated kinases facilitates SG formation (Ryan & Rubinsztein, 2024). Similarly, in plants, phosphorylation acts as a regulatory mechanism that can either enhance or inhibit SG formation, depending on the nature of the stress, the identity of the protein, and the phosphorylation site involved. Taken together, these findings highlight the central role of phosphorylation in modulating the behavior of biomolecular condensates during environmental stress. From signal transduction to RNA metabolism, phosphorylation serves as a versatile regulatory mechanism governing protein localization, activity, and condensate organization in plant cells.

## Ubiquitination-mediated dynamics of cytoplasmic biomolecular condensates

In addition to phosphorylation, ubiquitination also appears important for cytoplasmic biomolecular condensate dynamics (Fig. 1h,i; Table 1b). The first evidence of the importance of ubiquitination was reported during heat stress in Arabidopsis (McLoughlin et al., 2019). Analysis of insoluble proteins during heat stress reveals that those proteins are extensively ubiquitylated, especially many RNA-binding proteins known as SG components such as the poly(A) binding proteins PAB2/4/8, the TSN1/2, or the La-related protein 1 LARP1 (Fig. 1h). This large ubiquitination was recently confirmed (Xie et al., 2024) and is consistent with the presence of proteasome constituents in SG (McLoughlin et al., 2019; Xie et al., 2024). More particularly, heat stress triggers extensive ubiquitylation of SG components. Proteolytic activity in SG triggers their disassembly during the recovery phase, essential for translation recovery and heat tolerance (McLoughlin et al., 2019; Xie et al., 2024; Q. Chen et al., 2024; Pang et al., 2025). In fact, a *pad1* mutant (a subunit of the 20S core particle of the proteasome) exhibits a significantly reduced SG disassembly and displays a heat tolerance phenotype during the recovery phase. How ubiquitylated SG components regulate SG dynamics awaits further exploration (Xie et al., 2024). More recently, autophagy activation during heat stress was also proposed to participate in this phenomenon, demonstrating the importance of clearance of ubiquitinated aggregated proteins for stress recovery (Li et al., 2024). Notably, in an Oligouridylate-Binding Protein 1 (UBP1) triple mutant (*ubp1abc*), key components of SG formation, a delay in autophagy activation is observed. This results in a defect in the removal of ubiquitinated proteins produced during heat stress (Li et al., 2024).

Some proteins can undergo several PTMs, which have an impact on their granule formation dynamics. For example, TZF1, phosphorylated during flg22 treatment (Fig. 1c), was also reported

to be ubiquitinated by an E3 ubiquitin ligase KEEP-ON-GOING (KEG) (He et al., 2024). TZF1 ubiquitination induces its accumulation to SG (Fig. 1i). Mutations of TZF1 ubiquitination sites drastically affect SG assembly (He et al., 2024). In mammals, the importance of ubiquitination and autophagy was also demonstrated. Mutations implicated in several diseases compromise autophagy, resulting in the persistence of condensates (see (Ryan & Rubinsztein, 2024) for a complete review). Altogether, these different results illustrate the importance of ubiquitination and the clearance of ubiquitinated proteins in condensate dynamics and stress response.

## Other PTMs involved in the dynamics of cytoplasmic biomolecular condensates

Lysine acetylation is another PTM mediating cytoplasmic biomolecular condensate metabolism (Fig. 1j; Table 1c). In rice, the cytosolic Histone Deacetylase HDA714 confers plant tolerance to heat stress by controlling the protein lysine acetylation status of several glycolysis enzymes. Upon heat stress, HDA714 accumulates in SG and affects the lysine acetylation status of several SG proteins like TSN and small ribosomal proteins, influencing their own allocation in SG (Z. Chen et al., 2024) (Fig. 1j). Although the function of protein lysine acetylation in protein allocation to SG is unclear, previous studies indicated that lysine acetylation may promote protein polyubiquitination and degradation (Du et al., 2010; Xu et al., 2021). A possible coordination of lysine acetylation and ubiquitination in controlling SG dynamics is still to be investigated. In mammals, the cytosolic histone deacetylase HDAC6 was shown to regulate SG formation by deacetylating the RNA helicase DDX3X and the scaffold protein Ras GTPase-activating protein binding protein 1 (G3BP1), allowing their localization in SG. It was demonstrated that an N-terminal Intrinsically Disordered Region (IDR) of DDX3X (IDR1) can undergo LLPS *in vitro*, and its acetylation at multiple lysine residues impairs the formation of liquid droplets. Hence, an enhanced LLPS propensity through the deacetylation of DDX3X-IDR1 by HDAC6 is necessary for SG maturation (Kwon et al., 2007; Saito et al., 2019). Redox regulation of cytoplasmic biomolecular condensate metabolism has been shown to regulate flower meristem development in tomato (Fig. 1k; Table 1d). Huang et al. (2021) demonstrated that developmentally produced hydrogen peroxide ($H_2O_2$) in the shoot apical meristem (SAM) triggers reversible protein phase separation of TERMINATING FLOWER (TMF), a transcription factor that regulates flowering transition by repressing the pre-maturation of SAM. Specific cysteine residues (Cys112, 124, and 126) within TMF sense the cellular redox environment to form disulfide bonds that concate multiple TMF molecules and elevate the amount of intrinsically disordered regions to trigger phase separation (Fig. 1k). Moreover, redox-dependent phase separation enables TMF to bind and sequester the promoter of a floral identity gene *ANANTHA* and repress its expression (Huang et al., 2021). In mammals, the capacity of TIA1, a core stress granule protein, to localize in SG is redox-dependent. Reactive oxygen species (ROS) such as $H_2O_2$ oxidize the conserved Cys36 in TIA1 and inhibit SG
assembly by impairing its RNA-binding activity. Hence, suppres-
sion of SG formation by oxidative stress underlies neuronal cell
death in neurodegenerative diseases (Arimoto-Matsuzaki
et al., 2016). Interestingly, the redox-regulated Cys is conserved
in UBP1 proteins, plant homologs of TIA1, suggesting that redox
regulation of UBP1 might occur in plants.

Other types of cytosolic condensates have been shown to be
under redox regulation. In plants, a salicylic acid (SA)-induced
transition of Non-expressor of Pathogenesis Related 1 (NPR1) to
cytosolic condensates is required for the formation of the
NPR1-Cullin 3 E3 ligase complex to ubiquitinate and promote
cell survival under pathogen effector-triggered immunity. This
transition is mediated by conserved redox-sensitive cysteines
(Cys511, 521, and 529) present within NPR1 IDRs. It was
proposed that SA triggers a conformational change in NPR1
through modulation of the redox state of these cysteine residues
(Fig. 1l). Meanwhile, NPR1 is also prone to SUMOylation in the
nucleus, affecting its subsequent ubiquitination and degradation,
and also interplaying with condensate formation in the cytoplasm
(Fig. 1m) (Zavaliev et al., 2020). In mammals, fused in sarcoma
(FUS), a DNA/RNA-binding protein, is associated with neurode-
generative diseases such as amyotrophic lateral sclerosis (ALS) and
frontotemporal dementia (FTD). Under neurodegenerative dis-
eases, stress-induced ROS generation triggers excessive glutathio-
nylation (binding of a glutathione residue) at the Cys447 residue in
the DNA-binding domain of FUS. This modification was
proposed to induce conformational changes that favor FUS
aggregation by promoting LLPS. Moreover, the glutathione
transferase O2 (GstO2) reduced cytoplasmic FUS aggregation by
deglutathionylation, and the overexpression of a GstO2 homolog
attenuates FUS-induced neurotoxicity and cytoplasmic FUS
accumulation in mouse neuronal cells. Thus, the modulation of
FUS glutathionylation was proposed to be a promising therapeutic
strategy for FUS-associated neurodegenerative diseases (Cha
et al., 2022).

Additional PTMs involved in the dynamics of
cytoplasmic biomolecular condensates identified in
other organisms

In other organisms, phosphorylation and ubiquitination have also
been shown to play key roles in condensate dynamics (see (Wang
et al., 2023), for a comprehensive review). In addition, several other
PTMs have been described. SUMOylation, a PTM structurally
similar to ubiquitination, has been well characterized in mammals
and is proposed to influence SG disassembly (Marmor-Kollet
et al., 2020). Impaired SUMOylation delays SG disassembly, a
phenomenon observed in neurodegenerative diseases (Marmor-
Kollet et al., 2020). NEDDylation, the addition of an NEDD8
polypeptide, has also been proposed to influence condensate
dynamics, although its precise role remains under debate
(Jayabalan et al., 2016; Markmiller et al., 2019). Under stress
conditions, glycosylation of ribosomal subunits facilitates the
recruitment of the translational initiation complex into SGs in
human cells (Ohn et al., 2008). Finally, methylation of arginine
residues within the RGG domains of several proteins has been

found to repress SG assembly (Tsai et al., 2016; Hofweber
et al., 2018; Lenard et al., 2021). While this modification has not
yet been shown to affect condensates in plants, it is known to play
important roles in plant development (Wang et al., 2007; Deng
et al., 2010; Hu et al., 2019; Agrofoglio et al., 2024; Barre-
Villeneuve et al., 2024; Barré-Villeneuve & Azevedo-
Favory, 2024).

Conclusions and future directions

In the past few years, important progress has been made in the
dynamics of cytoplasmic biomolecular condensates in plants,
revealing a myriad of constituents present in these aggregates.
While many factors were proposed to be involved in condensate
formation, the PTM of these factors appears as an additional layer
of regulation. In particular, several enzymes involved in PTMs
were identified, such as kinases, ubiquitination components,
lysine deacetylases, and redox regulators, but their contribution to
biomolecular condensate dynamics is far from being understood.
The consequence of these modifications on protein structure,
RNA-binding activities, and association with other partners
within condensates will need further investigation. Interestingly,
some examples (e.g. TZF1 and NPR1) document the contribu-
tion of different types of PTMs in regulating their localization to
biomolecular condensates. How are these different mechanisms
coordinated? Are they specific to distinct stress conditions?
Moreover, additional PTMs (e.g. glycosylation and Arg methyla-
tion) arising in biomolecular condensates in mammals might
also be discovered in plants (Wang et al., 2023). The recent
development of enrichment methods for analyzing specific PTMs
will likely enable better characterization of the role of novel
PTMs in condensate dynamics (Brandi et al., 2022). In addition
to proteins, mRNA molecules also play a role in the dynamics of
condensates (Bounedjah et al., 2014). Like proteins, mRNAs can
undergo chemical modifications, such as N6-methyladenosine
(m6A). This modification has recently been proposed to mediate
RNA localization within SGs in plants and may be reversible,
possibly due to the presence of demethylases localized in SGs (Fan
et al., 2025). However, how chemical modifications of mRNAs
and proteins are coordinated to regulate condensate dynamics
remains an open question. Hence, a deeper characterization of the
mechanism leading to cytoplasmic biomolecular condensate
formation would allow better understanding of the exact
functions of these distinct aggregates. Finally, our current
understanding of the crosstalk between condensate dynamics
and PTMs remains largely descriptive, with significant uncer-
tainty surrounding the causal relationships between both
mechanisms. To address this gap, it is crucial to better investigate
the motifs (such as IDRs) necessary for phase separation and
examine their potential PTM sites and clarify their regulatory
roles and biological functions. Interestingly, the presence of many
metabolic enzymes found in biomolecular condensate proteomes
might reveal a role of their compartmentation to fine-tune the
metabolism under developmental or stress constraints. Recently,
new techniques have been developed in plants, such as the
Targeted Condensation-prone-protein Degradation system,
which is based on the fusion of a targeted protein to an E3
ubiquitin ligase that induces self-degradation after condensation
(also called E3TCD1). This technique could also be a good
strategy to better characterize the key players involved in
condensation formation and the physiological importance of
these aggregates in plant development and stress response (Luo
et al., 2025).

Acknowledgements

This study is set within the framework of the ‘Laboratoires d’Excellences (LABEX)’ TULIP (ANR-10-LABX-41) and of the ‘École Universitaire de Recherche (EUR)’ TULIP-GS (ANR-18-EURE-0019). The work of RM is supported by the Agence Nationale de la Recherche (ANR-21-CE20-0003 and ANR-25-CE20-0508). The work of JPR is supported by the Agence Nationale de la Recherche (ANR-19-CE12-0027, ANR-20CE12-0025, and ANR-24-CE20-2677-02).

Competing interests

None declared.

Author contributions

ML, JPR and RM wrote the manuscript.

ORCID

Margaux Legoux ID https://orcid.org/0009-0008-1630-6860

Rémy Merret https://orcid.org/0000-0002-3790-1115

Jean-Philippe Reichheld ID https://orcid.org/0000-0001-6884-0602

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