The Arabidopsis PRCl-like ring-finger proteins are necessary for repression of embryonic traits during vegetative growth

Polycomb 组基因在维护起关键作用 transcriptionally 为在动物和植物的合适的房间区别的基因的 silenced 状态。当时 polycomb 的部件压抑的 complex2 (PRC2 ) evolutionarily 被保存，他们的功能广泛地在植物被学习， PRC1 在动物和植物之间更加不同，并且它在植物的功能是不好迄今为止描述了。以前的研究作为动物 PRC1 子单元 RING1 的相当或相同事物识别了 Arabidopsis AtRING1a 和 AtRING1b。这里，我们证明 Atring1a Atring1b 双异种在植物的生长期间展出胚胎的特点的 derepression。因此，几关键规章的基因在 embryogenesis 包含了，干细胞活动宫外地在异种被表示。而且，我们证明变异的显型和规章的基因的增加的表示被 PRC2 变异的 clf 提高。最后，我们显示出那动物 PRC1 子单元戒指手指蛋白质 BMI1， AtBMI1a， AtBMI1b 和 AtBMI1c 的三个相当或相同事物，罐头与 AtRING1a 或 AtRING1b 绑，并且另外， AtBMI1c 能与 LHP1 绑。Atbmi1a Atbmi1b 双异种显示出类似于 Atring1a Atring1b 双异种的胚胎的特点的 derepression。有趣地， AtBMI1a， AtBMI1b 和 AtBMI1c 的表示层次在 Atring1a Atring1b 异种被提高，那些在 Atbmi1a Atbmi1b 异种 AtBMI1c， AtRING1a 和 AtRING1b 被提高，建议自我规章的反馈机制。一起拿，我们的结果为合适的体的生长在胚胎的特点和规章的基因的稳定的压抑照亮象 PRC1 一样戒指手指部件的关键功能。

No-go decay as a novel route to restrict viral infection in plants

Plants use several layers of defense to detect and combat viruses(Figure 1).Specialized host-encoded receptors sense viral virulence effector proteins and induce a signal transduction cascade,leading to effector-triggered immunity(Lopez-Gomollon and Baulcombe,2022).Plants also use several RNA-based processes to seek and destroy viral RNAs.The major pathway restricting viral multiplication is RNA silencing,a widely conserved mechanism of gene extinction that uses dsRNA to produce 21 to 24 nucleotides small interfering RNAs and guide viral RNA degradation(Lopez-Gomollon and Baulcombe,2022).

A Pivotal Role of DELLAs in Regulating Multiple Hormone Signals

Plant phenotypic plasticity is controlled by diverse hormone pathways, which integrate and convey infor- mation from multiple developmental and environmental signals. Moreover, in plants many processes such as growth, development, and defense are regulated in similar ways by multiple hormones. Among them, gibberellins （GAs） are phytohormones with pleiotropic actions, regulating various growth processes throughout the plant life cycle. Previous work has revealed extensive interplay between GAs and other hor- mones, but the molecular mechanism became apparent only recently. Molecular and physiological studies have demonstrated that DELLA proteins, considered as master negative regulators of GA signaling, inte- grate multiple hormone signaling pathways through physical interactions with transcription factors or reg- ulatory proteins from different families. In this review, we summarize the latest progress in GA signaling and its direct crosstalk with the main phytohormone signaling, emphasizing the multifaceted role of DELLA proteins with key components of major hormone signaling pathways.

Histone Acetyltransferase AtGCN5/HAG1 Is a Versatile Regulator of Developmental and Inducible Gene Expression in Arabidopsis

Histone acetylation/deacetylation is a dynamic process and plays an important role in gene regulation. Histone acetylation homeostasis is regulated by antagonist actions of histone acetyltransferases （HAT） and deacetylases （HDAC）. Plant genome encodes multiple HATs and HDACs. The Arabidopsis HAT gene AtGCNS/HAGlplays an essential role in many plant development processes, such as meristem function, cell differentiation, leaf and floral organogenesis, and responses to environmental conditions such as light and cold, indicating an important role of this HAT in the regulation of both long-term developmental switches and short-term inducible gene expression. AtGCN5 targets to a large number of promoters and is required for acetylation of several histone H3 lysine residues. Recruitment of AtGCN5 to target promoters is likely to be mediated by direct or indirect interaction with DNA-binding transcription factors and/or by interaction with acetylated histone lysine residues on the targets. Interplay between AtGCN5 and other HATand HDAC is demonstrated to control specific regulatory pathways. Analysis of the role of AtGCN5 in light-inducible gene expression suggests a function of AtGCN5 in preparing chromatin commitment for priming inducible gene activation in plants.

Chromatin Remodeling in Stem Cell Maintenance in Arabidopsis thaliana

Pluripotent stem cells are able to both self-renew and generate undifferentiated cells for the formation of new tissues and organs. In higher plants, stem cells found in the shoot apical meristem （SAM） and the root apical meristem （RAM） are origins of organogenesis occurring post-embryonically. It is important to understand how the regulation of stem cell fate is coordinated to enable the meristem to constantly generate different types of lateral organs. Much knowledge has accumulated on specific transcription factors controlling SAM and RAM activity. Here, we review recent evidences for a role of chromatin remodeling in the maintenance of stable expression states of transcription factor genes and the control of stem cell activity in Arabidopsis.

Activation of Defense Response Pathways by OGs and Fig22 Elicitors in Arabidopsis Seedlings

We carried out transcriptional profiling analysis in 10-d-old Arabidopsis thaliana seedlings treated with oligogalacturonides （OGs）, oligosaccharides derived from the plant cell wall, or the bacterial flagellin peptide Fig22, general elicitors of the basal defense response in plants. Although detected by different receptors, both OGs and Fig22 trigger a fast and transient response that is both similar and comprehensive, and characterized by activation of early stages of multiple defense signaling pathways, particularly JA-associated processes. However, the response to Fig22 is stronger in both the number of genes differentially expressed and the amplitude of change. The magnitude of induction of individual genes is in both cases dose-dependent, but, even at very high concentrations, OGs do not induce a response that is as comprehensive as that seen with Fig22. While high doses of either microbe-associated molecular pattern （MAMP） elicit a late response that includes activation of senescence processes, SA-dependent secretory pathway genes and PR1 expres- sion are substantially induced only by Fig22. These results suggest a lower threshold for activation of early responses than for sustained or SA-mediated late defenses. Expression patterns of amino-cyclopropane-carboxylate synthase genes also implicate ethylene biosynthesis in regulation of the late innate immune response.

Dynamic Regulation of DELLA Protein Activity： SPINDLY and SECRET AGENT Unmasked!

Plants are sessile organisms that integrate growth responses to multiple endogenous and environmental signals. The DELLA family of transcription regulators, first identified as key repressors of gibberellin （GA） signaling, have emerged as a central node of integration, thus providing a mechanism for environmentally responsive growth regulation （Oh et al., 2014）.

Subcellular Redistribution of Root Aquaporins nduced by Hydrogen Peroxide

Aquaporins are water channel proteins that mediate the fine-tuning of cell membrane water permeability during development or in response to environmental stresses. The present work focuses on the oxidative stress-induced redistribution of plasma membrane intrinsic protein （PIP） aquaporins from the plasma membrane （PM） to intracellular membranes. This process was investigated in the Arabidopsis root. Su- crose density gradient centrifugation showed that exposure of roots to 0.5 mM H2O2 induces significant depletion in PM fractions of several abundant PIP homologs after 15 rain. Analyses by single-particle tracking and fluorescence correlative spectroscopy showed that, in the PM of epidermal cells, H2O2 treat- ment induces an increase in lateral motion and a reduction in the density of a fluorescently tagged form of the prototypal AtPIP2;1 isoform, respectively. Co-expression analyses of AtPIP2;1 with endomembrane markers revealed that H2O2 triggers AtPIP2;1 accumulation in the late endosomal compartments. Life- time analyses established that the high stability of PIPs was maintained under oxidative stress conditions, suggesting that H2O2 triggers a mechanism for intracellular sequestration of PM aquaporins without further degradation. In addition to information on cellular regulation of aquaporins, this study provides novel and complementary insights into the dynamic remodeling of plant internal membranes during oxida- tive stress responses.

Nitrate Transport, Sensing, and Responses in Plants

Nitrogen （N） is an essential macronutrient that affects plant growth and development. N is an important component of chlorophyll, amino acids, nucleic acids, and secondary metabolites. Nitrate is one of the most abundant N sources in the soil. Because nitrate and other N nutrients are often limiting, plants have developed sophisticated mechanisms to ensure adequate supply of nutrients in a variable environment. Nitrate is absorbed in the root and mobilized to other organs by nitrate transporters. Nitrate sensing activates signaling pathways that impinge upon molecular, metabolic, physiological, and developmental responses locally and at the whole plant level. With the advent of genomics technologies and genetic tools, important advances in our understanding of nitrate and other N nutrient responses have been achieved in the past decade. Furthermore, techniques that take advantage of natural polymor- phisms present in divergent individuals from a single species have been essential in uncovering new components. However, there are still gaps in our understanding of how nitrate signaling affects biolog- ical processes in plants. Moreover, we still lack an integrated view of how all the regulatory factors iden- tified interact or crosstalk to orchestrate the myriad N responses plants typically exhibit. In this review, we provide an updated overview of mechanisms by which nitrate is sensed and transported throughout the plant. We discuss signaling components and how nitrate sensing crosstalks with hormonal pathways for developmental responses locally and globally in the plant. Understanding how nitrate impacts on plant metabolism, physiology, and growth and development in plants is key to improving crops for sustainable agriculture.

Epigenomic Modification and Epigenetic Regulation in Rice

Epigenomes including genome-wide histone modification and DNA methylation profiles are important for genome activity and fof defining gene expression patterns of plant development and responses to various environmental conditions. Rice is the most important crop plant and serves as a model for cereal genomics. Rice epigenomic landscape is emerging and the function of chromatin modification regulators in gene expression, transposon repression and plant development is being characterized. Epigenomic variation that gives rise to stable or transgenerational heritable epialleles related to variation of important agronomical traits or stress responses is being characterized in rice. Implication of epigenomic variation in rice heterosis is being exploited.

Non-Protein-Coding RNAs and their Interacting RNA-Binding Proteins in the Plant Cell Nucleus

The complex responses of eukaryotic cells to external factors are governed by several transcriptional and post-transcriptional processes. Several of them occur in the nucleus and have been linked to the action of non-proteincoding RNAs （or npcRNAs）, both long and small npcRNAs, that recently emerged as major regulators of gene expression. Regulatory npcRNAs acting in the nucleus include silencing-related RNAs, intergenic npcRNAs, natural antisense RNAs, and other aberrant RNAs resulting from the interplay between global transcription and RNA processing activities （such as Dicers and RNA-dependent polymerases）. Generally, the resulting npcRNAs exert their regulatory effects through interactions with RNA-binding proteins （or RBPs） within ribonucleoprotein particles （or RNPs）. A large group of RBPs are implicated in the silencing machinery through small interfering RNAs （siRNAs） and their localization suggests that several act in the nucleus to trigger epigenetic and chromatin changes at a whole-genome scale. Other nuclear RBPs interact with npcRNAs and change their localization. In the fission yeast, the RNA-binding Mei2p protein, playing pivotal roles in meiosis, interact with a meiotic npcRNA involved in its nuclear re-localization. Related processes have been identified in plants and the ENOD40 npcRNA was shown to re-localize a nuclear-speckle RBP from the nucleus to the cytoplasm in Medicago truncatula. Plant RBPs have been also implicated in RNA-mediated chromatin silencing in the FLC locus through interaction with specific antisense transcripts. In this review, we discuss the interactions between RBPs and npcRNAs in the context of nuclear-related processes and their implication in plant development and stress responses. We propose that these interactions may add a regulatory layer that modulates the interactions between the nuclear genome and the environment and, consequently, control plant developmental plasticity.

A Truncated Arabidopsis NUCLEOSOME ASSEMBLY PROTEIN 1, AtNAP1;3T, Alters Plant Growth Responses to Abscisic Acid and Salt in the Atnap 1;3-2 Mutant

Chromatin remodeling is thought to have crucial roles in plant adaptive response to environmental stimulus. Here, we report that, in Arabidopsis, the evolutionarily conserved histone chaperone, NUCLEOSOME ASSEMBLY PROTEIN 1 （NAP1）, is involved in plant response to abscisic acid （ABA）, a phytohormone important in stress adaptation. We show that simultaneous loss-of-function of AtNAP1;1, AtNAP1;20 and AtNAP1;3 （the triple mutant m123-1） caused a slight hypersensitive response to ABA in seedling growth. Strikingly, the other triple mutant m123-2 containing a different mutant allele of AtNAP1;3, the Atnap 1;3-2 allele, showed a hyposensitive response to ABA and a decreased tolerance to salt stress. This ABA- hyposensitive and salt response phenotype specifically associated with the Atnapl;3-2 mutant allele. We show that this mutant allele produced a truncated protein, AtNAP1;3T, which lacks 34 amino acids at the C-terminus compared to the wild-type protein AtNAP1;3. We further show that the heterozygous plants containing the Atnapl;3-2 mutant allele as well as transgenic plants overexpressing AtNAP1;3Texhibit ABA-hyposensitive phenotype. It thus indicates that AtNAP1;3T functions as a dominant negative factor in ABA response. The expression of some ABA-responsive genes, including genes encoding protein kinases and transcription regulators, was found perturbed in the mutant and in theAtNAP1;3Ttransgenic plants. Taken together, our study uncovered AtNAP1 proteins as positive regulators and AtNAP1;3Tas a negative regulator in ABA signaling pathways, providing a novel link of chromatin remodeling to hormonal and stress responses.

Crucial function of histone lysine methylation in plant reproduction

Unlike animals, plants do not set aside germ cells early in development. In angiosperm species, reproduction occurs in the adult plant upon flowering. The multicellular male and female gametophytes differentiate from meiotic products within reproductive floral organs. Double fertilization is another remarkable feature of most angiosperm species. The zygote derived from fertilization of the egg cell by one of the sperm cells and the endosperm from fertilization of the central cell by the second sperm cell develop in a coordinated manner together and enclosed in the sporophytic maternal integuments, forming the seed. Understanding plant reproduction is biologically pertinent and agronomically and ecologically important. Here, we describe the known functions of histone lysine methylations in various steps of reproduction in the reference plant Arabidopsis thaliana. It is emerging that histone lysine methylation is key for understanding epigenetic regulation networks of genome function.

The Multilayer’s Control of ARGONAUTE 1 Contents

ARGONAUTE proteins(AGO)are key effectors of the RNA silencing pathways involved in the regulation of gene expression and in antiviral defense(Vaucheret,2008).Among the 10 AGO proteins present in Arabidopsis,AG01 is essential for plant development and defense response,participating in both microRNA(miRNA)-and small interfering RNA(siRNA)-mediated gene silencing(Vaucheret,2008).Given that AG01 depletion is lethal,only hypomorphic mutant plants are viable and display a large variety of developmental phenotypes(Vaucheret,2008).Importantly,the fine tuning of AG01 content is an important process orchestrated by several different pathways(Cho et al.,2016).It was recently described that the mode of action of AG01 is not only restricted to the posttranscriptional gene silencing pathway taking place in the cytoplasm.Indeed,several nuclear AG01 functions have been identified(Bajczyk et al.,2019).Thus,the characterization of the different AG01 pools implies that specific subcellular pathways might trigger AGOI turnover and that complex regulatory processes might interplay to specifically fine tune AG01 content.

Vacuole Integrity Maintained by DUF300 Proteins Is Required for Brassinosteroid Signaling Regulation

Brassinosteroid （BR） hormone signaling controls multiple processes during plant growth and development and is initiated at the plasma membrane through the receptor kinase BRASSINOSTEROID INSENSITIVE1 （BRI1） together with co-receptors such as BRI1-ASSOClATED RECEPTOR KINASE1 （BAK1）. BRI1 abun- dance is regulated by endosomal recycling and vacuolar targeting, but the role of vacuole-related proteins in BR receptor dynamics and BR responses remains elusive. Here, we show that the absence of two DUF300 domain-containing tonoplast proteins, LAZARUS1 （LAZl） and LAZl HOMOLOG1 （LAZlH1）, causes vacuole morphology defects, growth inhibition, and constitutive activation of BR signaling. Intriguingly, tonoplast accumulation of BAK1 was substantially increased and appeared causally linked to enhanced BRI1 trafficking and degradation in lazl lazlhl plants. Since unrelated vacuole mutants exhibited normal BR responses, our findings indicate that DUF300 proteins play distinct roles in the regulation of BR signaling by maintaining vacuole integrity required to balance subcellular BAK1 pools and BR receptor distribution.

H3K36 Methylation Is Involved in Promoting Rice Flowering

Dear Editor, Histone H3 lysine 36 （H3K36） methylation is a conserved epigenetic mark in all eukaryotes （Berr et al., 2011; Wagner and Carpenter, 2012）. Reverse genetic analysis in Arabidopsis had uncovered a crucial role of H3K36 di- and tri-methylation （H3K36me2 and H3K36me3） in flowering-time regulation （reviewed in Berr et al., 2011）.

SDG714 Regulates Specific Gene Expression and Consequently Affects Plant Growth via H3K9 Dimethylation

Histone lysine methylation is known to be involved in the epigenetic regulation of gene expression in all eukaryotes including plants. Here we show that the rice SDG714 is primarily responsible for dimethylation but not trimethylaUon on histone H3K9 in vivo. Overexpression of YFP-SDG714 in Arabidopsis significantly inhibits plant growth and this inhibition is associated with an enhanced level of H3K9 dimethylation. Our microarray results show that many genes essential for the plant growth and development were downregulated in transgenic Arabidopsis plants overexpressing YFP-SDG714. By chromatin immunoprecipitation analysis, we show that YFP-SDG714 is targeted to specific chromatin regions and dimethylate the H3Kg, which is linked with heterochromatinization and the downregulation of genes. Most interestingly, when YFP-SDG714 production is stopped, the inhibited plants can partially restore their growth, suggesting that the perturbation of gene expression caused by YFP-SDG714 is revertible. Taken together, our results point to an important role of SDG714 in H3K9 dimethylation, suppression of gene expression and plant growth, and provide a potential method to regulate gene expression and plant development by an on-off switch of SDG714 expression.

Super-Resolved and Dynamic Imaging of Membrane Proteins in Plant Cells Reveal Contrasting Kinetic Profiles and Multiple Confinement Mechanisms

Dear Editor,Microscopic techniques allow either a global mobility analysis of proteins with fluorescence recovery after photobleaching （FRAP） or single-protein mobility characterization with single-particle or quantum dot tracking. For instance, total internal reflection fluo- rescence microscopy allowed single-particle tracking （SPT） of Arabidopsis plasma membrane （PM） proteins, revealing their heterogeneous distribution, low lateral diffusion, and dynamic properties in response to salt stress （Li et al., 2011）. Studies of SPT based on green fluorescent protein are unfortunately restricted by the density of proteins at the surface, since diffracted emission fluorescence prevents tracking of individual proteins separated by less than 1 μm. The recent emergence of high-density SPT techniques based on temporal emission decorrelation, such as single-particle tracking with photoactivated localization microscopy （sptPALM）, allowed the diffraction limit of classic light microscopy to be broken and reach nanometerlevel spatial resolutions （Manley et al., 2008）. Application of these techniques has rendered possible the characterization of the structural and dynamic heterogeneity of PM proteins with an accuracy of -20-80 nm （Rossier et al., 2012）. Such super-resolved dynamic imaging of membrane proteins has not yet been applied to any plant system. Here, we report the first use in plants of the live-cell sptPALM technique, providing a high-density super-resolved nanoscale map of individual membrane-protein motions.