PLETHORA‐WOX5 interaction and subnuclear localization control Arabidopsis root stem cell maintenance

Imaging plant cell walls using fluorescent stains: The beauty is in the details

Plants continuously face various environmental stressors throughout their lifetime. To be able to grow and adapt in different environments, they developed specialized tissues that allowed them to maintain a protected yet interconnected body. These tissues undergo specific primary and secondary cell wall modifications that are essential to ensure normal plant growth, adaptation and successful land colonization. The composition of cell walls can vary among different plant species, organs and tissues. The ability to remodel their cell walls is fundamental for plants to be able to cope with multiple biotic and abiotic stressors. A better understanding of the changes taking place in plant cell walls may help identify and develop new strategies as well as tools to enhance plants' survival under environmental stresses or prevent pathogen attack. Since the invention of microscopy, numerous imaging techniques have been developed to determine the composition and dynamics of plant cell walls during normal growth and in response to environmental stimuli. In this review, we discuss the main advances in imaging plant cell walls, with a particular focus on fluorescent stains for different cell wall components and their compatibility with tissue clearing techniques. Lay Description: Plants are continuously subjected to various environmental stresses during their lifespan. They evolved specialized tissues that thrive in different environments, enabling them to maintain a protected yet interconnected body. Such tissues undergo distinct primary and secondary cell wall alterations essential to normal plant growth, their adaptability and successful land colonization. Cell wall composition may differ among various plant species, organs and even tissues. To deal with various biotic and abiotic stresses, plants must have the capacity to remodel their cell walls. Gaining insight into changes that take place in plant cell walls will help identify and create novel tools and strategies to improve plants' ability to withstand environmental challenges. Multiple imaging techniques have been developed since the introduction of microscopy to analyse the composition and dynamics of plant cell walls during growth and in response to environmental changes. Advancements in plant tissue cleaning procedures and their compatibility with cell wall stains have significantly enhanced our ability to perform high-resolution cell wall imaging. At the same time, several factors influence the effectiveness of cleaning and staining plant specimens, as well as the time necessary for the process, including the specimen's size, thickness, tissue complexity and the presence of autofluorescence. In this review, we will discuss the major advances in imaging plant cell walls, with a particular emphasis on fluorescent stains for diverse cell wall components and their compatibility with tissue clearing techniques. We hope that this review will assist readers in selecting the most appropriate stain or combination of stains to highlight specific cell wall components of interest.

Gelatin Nanoparticles can Improve Pesticide Delivery Performance to Plants

Nanomaterials associated with plant growth and crop cultivation revolutionize traditional concepts of agriculture. However, the poor reiterability of these materials in agricultural applications necessitates the development of environmentally-friendly approaches. To address this, biocompatible gelatin nanoparticles (GNPs) as nanofertilizers with a small size (≈150 nm) and a positively charged surface (≈30 mV) that serve as a versatile tool in agricultural practices is designed. GNPs load agrochemical agents to improve maintenance and delivery. The biocompatible nature and small size of GNPs ensure unrestricted nutrient absorption on root surfaces. Furthermore, when combined with pesticides, GNPs demonstrate remarkable enhancements in insecticidal (≈15%) and weed-killing effects (≈20%) while preserving the efficacy of the pesticide. That GNPs have great potential for use in sustainable agriculture, particularly in inducing plant growth, specifically plant root growth, without fertilization and in enhancing the functions of agrochemical agents is proposed. It is suggested conceptual applications of GNPs in real-world agricultural practices.

Multi-scale mechanisms driving root regeneration: From regeneration competence to tissue repatterning

Plants possess an outstanding capacity to regenerate enabling them to repair damages caused by suboptimal environmental conditions, biotic attacks, or mechanical damages impacting the survival of these sessile organisms. Although the extent of regeneration varies greatly between localized cell damage and whole organ recovery, the process of regeneration can be subdivided into a similar sequence of interlinked regulatory processes. That is, competence to regenerate, cell fate reprogramming, and the repatterning of the tissue. Here, using root tip regeneration as a paradigm system to study plant regeneration, we provide a synthesis of the molecular responses that underlie both regeneration competence and the repatterning of the root stump. Regarding regeneration competence, we discuss the role of wound signaling, hormone responses and synthesis, and rapid changes in gene expression observed in the cells close to the cut. Then, we consider how this rapid response is followed by the tissue repatterning phase, where cells experience cell fate changes in a spatial and temporal order to recreate the lost stem cell niche and columella. Lastly, we argue that a multi-scale modeling approach is fundamental to uncovering the mechanisms underlying root regeneration, as it allows to integrate knowledge of cell-level gene expression, cell-to-cell transport of hormones and transcription factors, and tissue-level growth dynamics to reveal how the bi-directional feedbacks between these processes enable self-organized repatterning of the root apex.

Insights into multilevel spatial regulation within the root stem cell niche

All differentiated root cells derive from stem cells spatially organized within the stem cell niche (SCN), a microenvironment located within the root tip. Here, we compiled recent advances in the understanding of how the SCN drives the establishment and maintenance of cell types. The quiescent center (QC) is widely recognized as the primary driver of cell fate determination, but it is recently considered a convergence center of multiple signals. Cell identity of the cortex endodermis initials is mainly driven by the regulatory feedback loops between transcription factors (TFs), acting as mobile signals between neighboring cells, including the QC. As exemplified in the vascular initials, the precise spatial expression of these regulatory TFs is connected with a dynamic hormonal interplay. Thus, stem cell maintenance and cell differentiation are regulated by a plethora of signals forming a complex, multilevel regulatory network. Integrating the transcriptional and post-translational regulations, protein-protein interactions, and mobile signals into models will be fundamental for the comprehensive understanding of SCN maintenance and differentiation.

ATP Hydrolases Superfamily Protein 1 (ASP1) Maintains Root Stem Cell Niche Identity through Regulating Reactive Oxygen Species Signaling in Arabidopsis

The maintenance of the root stem cell niche identity in Arabidopsis relies on the delicate balance of reactive oxygen species (ROS) levels in root tips; however, the intricate molecular mechanisms governing ROS homeostasis within the root stem cell niche remain unclear. In this study, we unveil the role of ATP hydrolase superfamily protein 1 (ASP1) in orchestrating root stem cell niche maintenance through its interaction with the redox regulator cystathionine β-synthase domain-containing protein 3 (CBSX3). ASP1 is exclusively expressed in the quiescent center (QC) cells and governs the integrity of the root stem cell niche. Loss of ASP1 function leads to enhanced QC cell division and distal stem cell differentiation, attributable to reduced ROS levels and diminished expression of SCARECROW and SHORT ROOT in root tips. Our findings illuminate the pivotal role of ASP1 in regulating ROS signaling to maintain root stem cell niche homeostasis, achieved through direct interaction with CBSX3.

Comprehensive integration of single-cell transcriptomic data illuminates the regulatory network architecture of plant cell fate specification

Plant morphogenesis relies on precise gene expression programs at the proper time and position which is orchestrated by transcription factors (TFs) in intricate regulatory networks in a cell-type specific manner. Here we introduced a comprehensive single-cell transcriptomic atlas of Arabidopsis seedlings. This atlas is the result of meticulous integration of 63 previously published scRNA-seq datasets, addressing batch effects and conserving biological variance. This integration spans a broad spectrum of tissues, including both below- and above-ground parts. Utilizing a rigorous approach for cell type annotation, we identified 47 distinct cell types or states, largely expanding our current view of plant cell compositions. We systematically constructed cell-type specific gene regulatory networks and uncovered key regulators that act in a coordinated manner to control cell-type specific gene expression. Taken together, our study not only offers extensive plant cell atlas exploration that serves as a valuable resource, but also provides molecular insights into gene-regulatory programs that varies from different cell types.

Hydrogen Peroxide Signaling in the Maintenance of Plant Root Apical Meristem Activity

Hydrogen peroxide (H2O2) is a prevalent reactive oxygen species (ROS) found in cells and takes a central role in plant development and stress adaptation. The root apical meristem (RAM) has evolved strong plasticity to adapt to complex and changing environmental conditions. Recent advances have made great progress in explaining the mechanism of key factors, such as auxin, WUSCHEL-RELATED HOMEOBOX 5 (WOX5), PLETHORA (PLT), SHORTROOT (SHR), and SCARECROW (SCR), in the regulation of RAM activity maintenance. H2O2 functions as an emerging signaling molecule to control the quiescent center (QC) specification and stem cell niche (SCN) activity. Auxin is a key signal for the regulation of RAM maintenance, which largely depends on the formation of auxin regional gradients. H2O2 regulates the auxin gradients by the modulation of intercellular transport. H2O2 also modulates the expression of WOX5, PLTs, SHR, and SCR to maintain RAM activity. The present review is dedicated to summarizing the key factors in the regulation of RAM activity and discussing the signaling transduction of H2O2 in the maintenance of RAM activity. H2O2 is a significant signal for plant development and environmental adaptation.

HD-Zip II transcription factors control distal stem cell fate in Arabidopsis roots by linking auxin signaling to the FEZ/SOMBRERO pathway

In multicellular organisms, specialized tissues are generated by specific populations of stem cells through cycles of asymmetric cell divisions, where one daughter undergoes differentiation and the other maintains proliferative properties. In Arabidopsis thaliana roots, the columella - a gravity-sensing tissue that protects and defines the position of the stem cell niche - represents a typical example of a tissue whose organization is exclusively determined by the balance between proliferation and differentiation. The columella derives from a single layer of stem cells through a binary cell fate switch that is precisely controlled by multiple, independent regulatory inputs. Here, we show that the HD-Zip II transcription factors (TFs) HAT3, ATHB4 and AHTB2 redundantly regulate columella stem cell fate and patterning in the Arabidopsis root. The HD-Zip II TFs promote columella stem cell proliferation by acting as effectors of the FEZ/SMB circuit and, at the same time, by interfering with auxin signaling to counteract hormone-induced differentiation. Overall, our work shows that HD-Zip II TFs connect two opposing parallel inputs to fine-tune the balance between proliferation and differentiation in columella stem cells.

FER-like iron deficiency-induced transcription factor (FIT) accumulates in nuclear condensates

The functional importance of nuclear protein condensation remains often unclear. The bHLH FER-like iron deficiency-induced transcription factor (FIT) controls iron acquisition and growth in plants. Previously described C-terminal serine residues allow FIT to interact and form active transcription factor complexes with subgroup Ib bHLH factors such as bHLH039. FIT has lower nuclear mobility than mutant FITmSS271AA. Here, we show that FIT undergoes a light-inducible subnuclear partitioning into FIT nuclear bodies (NBs). Using quantitative and qualitative microscopy-based approaches, we characterized FIT NBs as condensates that were reversible and likely formed by liquid-liquid phase separation. FIT accumulated preferentially in NBs versus nucleoplasm when engaged in protein complexes with itself and with bHLH039. FITmSS271AA, instead, localized to NBs with different dynamics. FIT colocalized with splicing and light signaling NB markers. The NB-inducing light conditions were linked with active FIT and elevated FIT target gene expression in roots. FIT condensation may affect nuclear mobility and be relevant for integrating environmental and Fe nutrition signals.

WOX2 functions redundantly with WOX1 and WOX4 to positively regulate seed germination in Arabidopsis

MAIN CONCLUSION

WOX family gene WOX2 is highly expressed during seed development, which functions redundantly with WOX1 and WOX4 to positively regulate seed germination. WOX (WUSCHEL-related homeobox) is a family of transcription factors in plants. They play essential roles in the regulation of plant growth and development, but their function in seed germination is not well understood. In this report, we show that WOX1, WOX2, and WOX4 are close homologues in Arabidopsis. WOX2 has a redundant function with WOX1 and WOX4, respectively, in seed germination. WOX2 is highly expressed during seed development, from the globular embryonic stage to mature dry seeds, and its expression is decreased after germination. Loss of function single mutant wox2, and double mutants wox1 wox2 and wox2 wox4-1 show decreased germination speed. WOX2 and WOX4 are essential for hypocotyl-radicle zone elongation during germination, potentially by promoting the expression of cell wall-related genes. We also found that WOX2 and WOX4 regulate germination through the gibberellin (GA) pathway. These results suggest that WOX2 and WOX4 integrate the GA pathway and downstream cell wall-related genes during germination.

Going through changes - the role of autophagy during reprogramming and differentiation

Somatic cell reprogramming is a complex feature that allows differentiated cells to undergo fate changes into different cell types. This process, which is conserved between plants and animals, is often achieved via dedifferentiation into pluripotent stem cells, which have the ability to generate all other types of cells and tissues of a given organism. Cellular reprogramming is thus a complex process that requires extensive modification at the epigenetic and transcriptional level, unlocking cellular programs that allow cells to acquire pluripotency. In addition to alterations in the gene expression profile, cellular reprogramming requires rearrangement of the proteome, organelles and metabolism, but these changes are comparatively less studied. In this context, autophagy, a cellular catabolic process that participates in the recycling of intracellular constituents, has the capacity to affect different aspects of cellular reprogramming, including the removal of protein signatures that might hamper reprogramming, mitophagy associated with metabolic reprogramming, and the supply of energy and metabolic building blocks to cells that undergo fate changes. In this Review, we discuss advances in our understanding of the role of autophagy during cellular reprogramming by drawing comparisons between plant and animal studies, as well as highlighting aspects of the topic that warrant further research.

Cultivating potential: Harnessing plant stem cells for agricultural crop improvement

Meristems are stem cell-containing structures that produce all plant organs and are therefore important targets for crop improvement. Developmental regulators control the balance and rate of cell divisions within the meristem. Altering these regulators impacts meristem architecture and, as a consequence, plant form. In this review, we discuss genes involved in regulating the shoot apical meristem, inflorescence meristem, axillary meristem, root apical meristem, and vascular cambium in plants. We highlight several examples showing how crop breeders have manipulated developmental regulators to modify meristem growth and alter crop traits such as inflorescence size and branching patterns. Plant transformation techniques are another innovation related to plant meristem research because they make crop genome engineering possible. We discuss recent advances on plant transformation made possible by studying genes controlling meristem development. Finally, we conclude with discussions about how meristem research can contribute to crop improvement in the coming decades.

Unlocking nature's (sub)cellular symphony: Phase separation in plant meristems

Plant development is based on the balance of stem cell maintenance and differentiation in the shoot and root meristems. The necessary cell fate decisions are regulated by intricate networks of proteins and biomolecules within plant cells and require robust and dynamic compartmentalization strategies, including liquid-liquid phase separation (LLPS), which allows the formation of membrane-less compartments. This review summarizes the current knowledge about the emerging field of LLPS in plant development, with a particular focus on the shoot and root meristems. LLPS regulates not only floral transition and flowering time while integrating environmental signals in the shoots but also influences auxin signalling and is putatively involved in maintaining the stem cell niche (SCN) in the roots. Therefore, LLPS has the potential to play a crucial role in the plasticity of plant development, necessitating further research for a comprehensive understanding.

A blast from the past: Understanding stem cell specification in plant roots using laser ablation

In the Arabidopsis root, growth is sustained by the meristem. Signalling from organiser cells, also termed the quiescent centre (QC), is essential for the maintenance and replenishment of the stem cells. Here, we highlight three publications from the founder of the concept of the stem cell niche in Arabidopsis and a pioneer in unravelling regulatory modules governing stem cell specification and maintenance, as well as tissue patterning in the root meristem: Ben Scheres. His research has tremendously impacted the plant field. We have selected three publications from the Scheres legacy, which can be considered a breakthrough in the field of plant developmental biology. van den Berg et al. (1995) and van den Berg et al. (1997) uncovered that positional information-directed patterning. Sabatini et al. (1999), discovered that auxin maxima determine tissue patterning and polarity. We describe how simple but elegant experimental designs have provided the foundation of our current understanding of the functioning of the root meristem.

Functional Modules in the Meristems: "Tinkering" in Action

BACKGROUND

A feature of higher plants is the modular principle of body organisation. One of these conservative morphological modules that regulate plant growth, histogenesis and organogenesis is meristems-structures that contain pools of stem cells and are generally organised according to a common principle. Basic content: The development of meristems is under the regulation of molecular modules that contain conservative interacting components and modulate the expression of target genes depending on the developmental context. In this review, we focus on two molecular modules that act in different types of meristems. The WOX-CLAVATA module, which includes the peptide ligand, its receptor and the target transcription factor, is responsible for the formation and control of the activity of all meristem types studied, but it has its own peculiarities in different meristems. Another regulatory module is the so-called florigen-activated complex, which is responsible for the phase transition in the shoot vegetative meristem (e.g., from the vegetative shoot apical meristem to the inflorescence meristem).

CONCLUSIONS

The review considers the composition and functions of these two functional modules in different developmental programmes, as well as their appearance, evolution and use in plant breeding.

Arabidopsis ASYMMETRIC LEAVES2 and Nucleolar Factors Are Coordinately Involved in the Perinucleolar Patterning of AS2 Bodies and Leaf Development

Arabidopsis ASYMMETRIC LEAVES2 (AS2) plays a key role in the formation of flat symmetric leaves. AS2 represses the expression of the abaxial gene ETTIN/AUXIN RESPONSE FACTOR3 (ETT/ARF3). AS2 interacts in vitro with the CGCCGC sequence in ETT/ARF3 exon 1. In cells of leaf primordia, AS2 localizes at peripheral regions of the nucleolus as two AS2 bodies, which are partially overlapped with chromocenters that contain condensed 45S ribosomal DNA repeats. AS2 contains the AS2/LOB domain, which consists of three sequences conserved in the AS2/LOB family: the zinc finger (ZF) motif, the ICG sequence including the conserved glycine residue, and the LZL motif. AS2 and the genes NUCLEOLIN1 (NUC1), RNA HELICASE10 (RH10), and ROOT INITIATION DEFECTIVE2 (RID2) that encode nucleolar proteins coordinately act as repressors against the expression of ETT/ARF3. Here, we examined the formation and patterning of AS2 bodies made from as2 mutants with amino acid substitutions in the ZF motif and the ICG sequence in cells of cotyledons and leaf primordia. Our results showed that the amino acid residues next to the cysteine residues in the ZF motif were essential for both the formation of AS2 bodies and the interaction with ETT/ARF3 DNA. The conserved glycine residue in the ICG sequence was required for the formation of AS2 bodies, but not for the DNA interaction. We also examined the effects of nuc1, rh10, and rid2 mutations, which alter the metabolism of rRNA intermediates and the morphology of the nucleolus, and showed that more than two AS2 bodies were observed in the nucleolus and at its periphery. These results suggested that the patterning of AS2 bodies is tightly linked to the morphology and functions of the nucleolus and the development of flat symmetric leaves in plants.

Preserving root stem cell functionality under low oxygen stress: the role of nitric oxide and phytoglobins

MAIN CONCLUSION

The preservation of quiescent center stem cell integrity in hypoxic roots by phytoglobins is exercised through their ability to scavenge nitric oxide and attenuate its effects on auxin transport and cell degradation. Under low oxygen stress, the retention or induction of phytoglobin expression maintains cell viability while loss or lack of induction of phytoglobin leads to cell degradation. Plants have evolved unique attributes to ensure survival in the environment in which they must exist. Common among the attributes is the ability to maintain stem cells in a quiescent (or low proliferation) state in unfriendly environments. From the seed embryo to meristematic regions of the plant, quiescent stem cells exist to regenerate the organism when environmental conditions are suitable to allow plant survival. Frequently, plants dispose of mature cells or organs in the process of acclimating to the stresses to ensure survival of meristems, the stem cells of which are capable of regenerating cells and organs that have been sacrificed, a feature not generally available to mammals. Most of the research on plant stress responses has dealt with how mature cells respond because of the difficulty of specifically examining plant meristem responses to stress. This raises the question as to whether quiescent stem cells behave in a similar fashion to mature cells in their response to stress and what factors within these critical cells determine whether they survive or degrade when exposed to environmental stress. This review attempts to examine this question with respect to the quiescent center (QC) stem cells of the root apical meristem. Emphasis is put on how varying levels of nitric oxide, influenced by the expression of phytoglobins, affect QC response to hypoxic stress.

The inhibition of maize (Zea mays L.) root stem cell regeneration by low oxygen is attenuated by Phytoglobin 1 (Pgb1) through changes in auxin and jasmonic acid

MAIN CONCLUSIONS

Over-expression of Phytoglobin1 increases the viability of maize root stem cells to low oxygen stress through changes in auxin and jasmonic acid responses. Hypoxia inhibits maize (Zea mays L.) root growth by deteriorating the quiescent center (QC) stem cells of the root apical meristem. Over-expression of the Phytoglobin1 ZmPgb1.1 alleviates these effects through the retention of the auxin flow along the root profile required for the specification of the QC stem cells. To identify QC-specific hypoxia responses and determine whether ZmPgb1.1 exercises a direct role on QC stem cells, we performed a QC functionality test. This was done by estimating the ability of QCs to regenerate a root in vitro in a hypoxic environment. Hypoxia decreased the functionality of the QCs by depressing the expression of several genes participating in the synthesis and response of auxin. This was accompanied by a decrease in DR5 signal, a suppression of PLETHORA and WOX5, two markers of QC cell identity, and a reduction in expression of genes participating in JA synthesis and signaling. Over-expression of ZmPgb1.1 was sufficient to mitigate all these responses. Through pharmacological alterations of auxin and JA, it is demonstrated that both hormones are required for QC functionality under hypoxia, and that JA acts downstream of auxin during QC regeneration. A model is proposed whereby the ZmPgb1.1 maintenance of auxin synthesis in hypoxic QCs is determinant for the retention of their functionality, with JA supporting the regeneration of roots from the QCs.

Molecular Mechanisms of Regulation of Root Development by Plant Peptides

Peptides perform many functions, participating in the regulation of cell differentiation, regulating plant growth and development, and also involved in the response to stress factors and in antimicrobial defense. Peptides are an important class biomolecules for intercellular communication and in the transmission of various signals. The intercellular communication system based on the ligand-receptor bond is one of the most important molecular bases for creating complex multicellular organisms. Peptide-mediated intercellular communication plays a critical role in the coordination and determination of cellular functions in plants. The intercellular communication system based on the receptor-ligand is one of the most important molecular foundations for creating complex multicellular organisms. Peptide-mediated intercellular communication plays a critical role in the coordination and determination of cellular functions in plants. The identification of peptide hormones, their interaction with receptors, and the molecular mechanisms of peptide functioning are important for understanding the mechanisms of both intercellular communications and for regulating plant development. In this review, we drew attention to some peptides involved in the regulation of root development, which implement this regulation by the mechanism of a negative feedback loop.

Development specifies, diversifies and empowers root immunity

Roots are a highly organised plant tissue consisting of different cell types with distinct developmental functions defined by cell identity networks. Roots are the target of some of the most devastating diseases and possess a highly effective immune system. The recognition of microbe- or plant-derived molecules released in response to microbial attack is highly important in the activation of complex immunity gene networks. Development and immunity are intertwined, and immunity activation can result in growth inhibition. In turn, by connecting immunity and cell identity regulators, cell types are able to launch a cell type-specific immunity based on the developmental function of each cell type. By this strategy, fundamental developmental processes of each cell type contribute their most basic functions to drive cost-effective but highly diverse and, thus, efficient immune responses. This review highlights the interdependence of root development and immunity and how the developmental age of root cells contributes to positive and negative outcomes of development-immunity cross-talk.

Come together now: Dynamic body-formation of key regulators integrates environmental cues in plant development

Plants as sessile organisms are constantly exposed to changing environmental conditions, challenging their growth and development. Indeed, not only above-ground organs but also the underground root system must adapt accordingly. Consequently, plants respond to these constraints at a gene-regulatory level to ensure their survival and well-being through key transcriptional regulators involved in different developmental processes. Recently, intrinsically disordered domains within these regulators are emerging as central nodes necessary not only for interactions with other factors but also for their partitioning into biomolecular condensates, so-called bodies, possibly driven by phase separation. Here, we summarize the current knowledge about body-forming transcriptional regulators important for plant development and highlight their functions in a possible environmental context. In this perspective article, we discuss potential mechanisms for the formation of membrane-less bodies as an efficient and dynamic program needed for the adaptation to external cues with a particular focus on the Arabidopsis root. Hereby, we aim to provide a perspective for future research on transcriptional regulators to investigate body formation as an expeditious mechanism of plant-environment interactions.

The plant stem-cell niche and pluripotency: 15 years of an epigenetic perspective

Pluripotent stem-cells are slowly dividing cells giving rise to daughter cells that can either differentiate to new tissues and organs, or remain stem-cells. In plants, stem-cells are located in specific niches of the shoot and root apical meristems (SAMs and RAMs). After ablation of stem-cell niches, pluripotent meristematic cells can establish new stem-cells, whereas the removal of the whole meristem destructs the regeneration process. In tissue cultures, after detached plant organs are transferred to rooting or callus induction medium (G5 or CIM), vasculature-associated pluripotent cells (VPCs) immediately start proliferation to form adventitious roots or callus, respectively, while other cell types of the organ explants basically play no part in the process. Hence, in contrast to the widely-held assumption that all plant cells have the ability to reproduce a complete organism, only few cell types are pluripotent in practice, raising the question how pluripotent stem-cells differ from differentiated cells. It is now clear that, in addition to gene regulatory networks of pluripotency factors and phytohormone signaling, epigenetics play a crucial role in initiation, maintenance and determination of plant stem-cells. Although, more and more epigenetic regulators have been shown to control plant stem-cell fate, only a few studies demonstrate how they are recruited and how they change the chromatin structure and transcriptional regulation of pluripotency factors. Here, we highlight recent breakthroughs but also revisited classical studies of epigenetic regulation and chromatin dynamics of plant stem-cells and their pluripotent precursor-cells, and point out open questions and future directions.