Plant Cells Research Articles

Molecular level analysis of the influence of natural biomaterials on aviation flame retardant performance

The use of natural biomaterials in flame retardant formulations as sustainable alternatives has gained significant interest in recent years. Given the high-risk environment in which airplanes operate, aviation safety remains a top priority. Flame retardants (FRs) are crucial for preventing or reducing the spread of flames in flammable materials used in aircraft construction and interior furnishings, thus mitigating fire risks. This study aims to analyze the molecular-level influence of natural biomaterials on aviation flame retardant performance, with a focus on lignin. Lignin, a natural polymer derived from plant cell walls, offers an environmentally friendly alternative to conventional synthetic flame retardants. Lignin-based composites can be applied to various aircraft components, such as wings and fuselage. The study employs Fourier Transform Infrared Spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and Nuclear Magnetic Resonance (NMR) to investigate the molecular interactions of these biomaterials. Additionally, to assess thermal stability and degradation, Thermo-gravimetric Analysis (TGA) is utilized. The results indicate that lignin enhances flame retardancy by promoting the formation of a protective char layer and improving thermal stability. This research also provides insights into the molecular mechanisms underlying lignin’s effectiveness as a flame retardant and explores its potential in developing high-performance aircraft flame retardants.

Epigenetic control of T-DNA during transgenesis and pathogenesis.

Mobile elements known as T-DNAs are transferred from pathogenic Agrobacterium to plants and reprogram the host cell to form hairy roots or tumors. Disarmed non-oncogenic T-DNAs are extensively used to deliver transgenes in plant genetic engineering. Such T-DNAs were the first known targets of RNA silencing mechanisms, which detect foreign RNA in plant cells and produce small RNAs that induce transcript degradation. These T-DNAs can also be transcriptionally silenced by the deposition of epigenetic marks such as DNA methylation and the dimethylation of lysine 9 (H3K9me2) in plants. Here, we review the targeting and the roles of RNA silencing and DNA methylation on T-DNAs in transgenic plants as well as during pathogenesis. In addition, we discuss the crosstalk between T-DNAs and genome-wide changes in DNA methylation during pathogenesis. We also cover recently discovered regulatory phenomena, such as T-DNA suppression and RNA silencing-independent and epigenetic-independent mechanisms that can silence T-DNAs. Finally, we discuss the implications of findings on T-DNA silencing for the improvement of plant genetic engineering.

Nano‐Patterned CuO Nanowire Nanogap Hydrogen Gas Sensor with Voids

AbstractHydrogen (H2) is increasingly employed in industrial applications, such as developing hydrogen fuel cells for vehicles and power plants. However, H2 explodes at a concentration limit of 4%, necessitating the development of ultrasensitive hydrogen sensors capable of early‐stage detection of hydrogen leaks. In this study, nano‐patterned polycrystalline cupric oxide (CuO) nanowire array nanogap gas sensors with voids are fabricated using electron‐beam lithography and ex situ oxidization by annealing, which could detect 5 ppb H2 and show response and recovery times of less than 10 s without a baseline shift. Combining a pre‐H2 annealing process in Ar/H2 for Cu nanowires and a low‐rate oxidation process enhances the crystallinity of CuO nanowires, facilitating the preparation of polycrystalline CuO nanowires with voids, which is a significantly practical approach for the improvements of gas sensing properties. Response and recovery times of <10 s can be obtained for a gap separation of ≈30 nm. These improvements are discussed based on a high electric field of ≈1.3 MV cm−1. The relationship between the normalized response and H2 concentration is discussed based on the power law. This paper presents highly reliable and fast H2 sensors without a baseline shift to meet the demands of the hydrogen industry.

Microbial communities and their role in enhancing hemp fiber quality through field retting.

The current development of industrial hemp "Cannabis Sativa L." fibers for technical textiles and industrial applications requires high-quality fibers with homogeneous properties. However, several factors have been reported to influence the fibers' intrinsic properties, including a post-harvest process known as retting. This process plays a crucial role in facilitating the mechanical extraction of fibers from hemp stems. Retting involves the degradation of the amorphous components surrounding the fiber bundles enabling their decohesion from stems. Microorganisms play a central role in mediating this bioprocess. During retting, they colonize the stems' surface. Therefore, the biochemical components of plant cell wall, acting as natural binding between fibers, undergo a breakdown through the production of microbial enzymes. Although its critical role, farmers often rely on empirical retting practices, and considering various biotic and abiotic factors, resulting in fibers with heterogenous properties. These factors limit the industrial applications of hemp fibers due to their inconsistent properties. Thus, the purpose of this review is to enhance our comprehension of how retting influences the dynamics of microbial communities and, consequently, the evolution of the biochemical properties of hemp stems throughout this process. Better understanding of retting is crucial for effective process management, leading to high-value fibers. KEY POINTS: • Retting enables degradation of cell wall components, controlling fiber properties. • Microbial enzymatic activity is crucial for successful decohesion of fiber bundles. • Understanding retting mechanisms is essential for consistent fiber production.

Acidic Stress Induces Cytosolic Free Calcium Oscillation, and an Appropriate Low pH Helps Maintain the Circadian Clock in Arabidopsis

Acidic stress is a formidable environmental factor that exerts adverse effects on plant growth and development, ultimately leading to a potential reduction in agricultural productivity. A low pH triggers Ca2+ influx across the plasma membrane (PM), eliciting distinct responses under various acidic pH levels. However, the underlying mechanisms by which Arabidopsis plant cells generate stimulus-specific Ca2+ signals in response to acidic stress remain largely unexplored. The experimentally induced stimulus may elicit spikes in cytosolic free Ca2+ concentration ([Ca2+]i) spikes or complex [Ca2+]i oscillations that persist for 20 min over a long-term of 24 h or even several days within the plant cytosol and chloroplast. This study investigated the increase in [Ca2+]i under a gradient of low pH stress ranging from pH 3.0 to 6.0. Notably, the peak of [Ca2+]i elevation was lower at pH 4.0 than at pH 3.0 during the initial 8 h, while other pH levels did not significantly increase [Ca2+]i compared to low acidic stress conditions. Lanthanum chloride (LaCl3) can effectively suppress the influx of [Ca2+]i from the apoplastic to the cytoplasm in plants under acid stress, with no discernible difference in intracellular calcium levels observed in Arabidopsis. Following 8 h of acid treatment in the darkness, the intracellular baseline Ca2+ levels in Arabidopsis were significantly elevated when exposed to low pH stress. A moderately low pH, specifically 4.0, may function as a spatial-temporal input into the circadian clock system. These findings suggest that acid stimulation can exert a continuous influence on intracellular calcium levels, as well as plant growth and development.

Engineering a xylose fermenting yeast for lignocellulosic ethanol production.

Lignocellulosic ethanol is produced by yeast fermentation of lignocellulosic hydrolysates generated by chemical pretreatment and enzymatic hydrolysis of plant cell walls. The conversion of xylose into ethanol in hydrolysates containing microbial inhibitors is a major bottleneck in biofuel production. We identified sodium salts as the primary yeast inhibitors, and evolved a Saccharomyces cerevisiae strain overexpressing xylose catabolism genes in xylose or glucose-mixed medium containing sodium salts. The fully evolved yeast strain can efficiently convert xylose in the hydrolysates to ethanol on an industrial scale. We elucidated that the amplification of xylA, XKS1 and pentose phosphate pathway-related genes TAL1, RPE1, TKL1, RKI1, along with mutations in NFS1, TRK1, SSK1, PUF2 and IRA1, are responsible and sufficient for the effective xylose utilization in corn stover hydrolysates containing high sodium salts. Our evolved or reverse-engineered yeast strains enable industrial-scale production of lignocellulosic ethanol and the genetic foundation we uncovered can also facilitate transfer of the phenotype to yeast cell factories producing chemicals beyond ethanol.

The structure of humates in aqueous solutions and their biological activity

When studying humate solutions, it is often not taken into account that humic substances (HS) can form supramolecular formations (SMFs) from molecular particles. These SMFs are highly stable, that is, the particles-molecules of HS do not separate from them spontaneously. It follows that at concentrations of the existence of SMFs, it is they, and not the particles-molecules of HS, that should be in solutions and determine their properties. The purpose of the study is to assess the influence of the form of existence of HS in solutions on their physico-chemical properties and biological activity. Solutions of sodium humate from brown coal were used in the work. The experimental results showed that with an increase in the concentration of humates, an abrupt increase in pH in the range of 30–50 mg l⁻¹ is observed. These concentrations correspond to the literature data on changes in the structure of HC in solutions: at concentrations above 30 mg l⁻¹ – barrier concentration – HS molecules form SMFs by self-assembly. Both molecular particles and SMFs, due to the diphilicity of HS, have the properties of surfactants. That is, in solutions at the interface of the “water–air” phases, HS films form. The strength of the films depends on the size of its constituent particles and the speed of their movement from the thickness to the surface of the solution. When plotting graphs in the coordinates “Film formation time in hours–Log humate concentration, mg l⁻¹”, a jump corresponding to the barrier concentration was detected on the curves. It was also found that during foliar treatment of cucumber shoots with mechanoactivated humate solutions with concentrations below the barrier, the stimulation effect increases, apparently due to the transition from the existence of HS in solution in the form of SMFs to existence in the form of particles-molecules that, due to their small size, can penetrate plant cells.

The Effects of Lead and Cross-Talk Between Lead and Pea Aphids on Defence Responses of Pea Seedlings

The main goal of this study was to investigate the effect of lead (Pb) at various concentrations, as an abiotic factor, and the cross-talk between Pb and pea aphid (Acyrthosiphon pisum (Harris)) (Hemiptera: Aphididae), as a biotic factor, on the defence responses of pea seedlings (Pisum sativum L. cv. Cysterski). The analysis of growth parameters for pea seedlings demonstrated that Pb at a low concentration, i.e., 0.025–0.0625 mM Pb(NO3)2, caused a hormesis effect, i.e., stimulation of seedling growth, whereas Pb at higher concentrations, i.e., 0.01–0.325 mM Pb(NO3)2, inhibited growth, which manifested as the inhibition of length and fresh biomass. The differences in the level of the main defence-related phytohormones, such as abscisic acid (ABA), jasmonic acid (JA) and salicylic acid (SA), and indole-3-acetic acid (IAA)—an auxin stimulating plant cell growth—depended on the dose of Pb, aphid infestation and direct contact of the stress factor with the organ. A high accumulation of soluble sugars in the organs of pea seedlings both at sublethal doses and hormetic doses at early experimental time points was observed. At 0 h and 24 h of the experiment, the hormetic doses of Pb significantly stimulated invertase activities, especially in the roots. Moreover, an increase was observed in the pisatin concentration in pea seedlings growing in the presence of different concentrations of Pb and in the case of cross-talk between Pb and A. pisum in relation to the control. Additionally, a significant induction of the expressions of isoflavone synthase (IFS) and 6α-hydroxymaackiain 3-O-methyltransferase (HMM) genes, which participate in the regulation of the pisatin biosynthesis pathway, in pea seedlings growing under the influence of sublethal 0.5 mM Pb(NO3)2 and hormetic 0.075 mM Pb(NO3)2 doses of Pb was noted. The obtained results showed that the response of P. sativum seedlings depends on the Pb dose applied, direct contact of the stress factor with the organ and the duration of contact.

Metaproteomics identifies key cell wall degrading enzymes and proteins potentially related to inter-field variability in fiber quality during flax dew retting

In this study, metaproteomics and biochemical analyses were used to identify for the first time specific proteins and associated micro-organisms responsible for cell wall degrading enzyme activity during dew retting of flax in two adjacent fields in northern France. This approach identified 6032 non-redundant proteins present at 4 key retting stages (R0/day 1, R2/day 6, R4/day 13, and R7/day 25), of which 75 contained CAZy (Carbohydrate Active Enzyme) motifs belonging to 31 different families from all 5 CAZy classes. 19 families were putatively related to the degradation of different plant cell wall polymers including lignin (AA1), pectins (CE13, CE8, PL1, PL3, GH28, GH35), hemicellulose (GH2, GH10, GH26, GH35, GH55, GH3, GH5, GH17) and cellulose (GH5, GH7, GH3, GH94, AA3). Taxonomy of identified proteins indicated that 85 % come from bacteria, 13 % from fungi, and 2 % from plants; however, ∼60 % of CAZymes involved in the degradation of plant wall polymers are of fungal origin. Although 88 % of total proteins and almost 65 % of cell wall degrading CAZymes were similar between the two investigated fields, certain differences in the abundance and dynamics of certain CAZymes might be related to observed inter-field variability in cell wall degrading enzyme activities, stem/fiber yield and industrial qualities of fibers harvested from the two fields. Overall, these results highlight the interest of using metaproteomics for improving our biological understanding of how retting impacts fiber quality. In addition, the identification of several new bacterial and fungal species in this study demonstrates that such an approach is also extremely powerful for generating novel taxonomic data.

A Simple Regeneration Process Using a CO2-Switchable-Polarity Solvent for Cellulose Hydrogels.

Cellulose is one of the main components of plant cell walls, abundant on earth, and can be acquired at a low cost. Furthermore, there has been increasing interest in its use in environmentally friendly, carbon-neutral, sustainable materials. It is expected that the applications of cellulose will expand with the development of a simple processing method. In this study, we dissolved cellulose in aqueous N-butyl-N-methylpyrrolidinium hydroxide solution ([C4mpyr][OH]/H2O) and investigated the cellulose regeneration process based on changes in solubility upon application of CO2 gas. We investigated the effect of transformation of the anion chemical structure on cellulose solubility by flowing CO2 gas into [C4mpyr][OH]/H2O and conducted pH, FT-IR, and 13C NMR measurements. We observed that the changes in anion structure allowed for the modulation of cellulose solubility in [C4mpyr][OH]/H2O, thus establishing a simple and safe cellulose regeneration process. This regeneration process was also applied to enable the production of cellulose hydrogels. The hydrogel formed using this method was revealed to have higher mechanical strength than an analogous hydrogel produced using the same dissolution solvent with the addition of a cross-linker. The ability to produce cellulose-based hydrogels of different mechanical properties is expected to expand the possible applications.

A biomacromolecular additive based on pullulan polysaccharide to enhance the life of lead-acid battery packs in DC systems

Abstract With the rapid growth in demand for mobile power, lead-acid batteries still occupy a large market share due to their excellence in energy storage. However, their lifespan is affected by various factors, which limits the application efficiency and environmental friendliness. In this regard, this paper proposes a method to enhance the service life of lead-acid battery packs by applying biomacromolecule additives. A lead-acid battery pack modification method is investigated by introducing chitosan, a natural macromolecule with excellent electrical conductivity and biodegradation properties, into lead-acid batteries. So that the chitosan-modified material forms a stable and protective film on the surface of the battery electrode plate, thereby reducing the analysis of sulphate crystals on the electrode surface. The method of modification of lead-acid battery packs has been studied. Comparative analysis of the experimental data shows that the modified battery pack exhibits lower charge transfer impedance and better electrochemical stability than the traditional lead-acid battery during the cyclic charge/discharge test. Through the cycle charge/discharge test, the energy loss of the battery with biomolecules is 30% lower than that of the unmodified battery, and the number of charge/discharge cycles increases by 60%, which effectively prolongs the service life of the lead-acid battery. The progress of this paper not only has guiding significance for the performance improvement of traditional lead-acid batteries but also provides a significant theoretical and experimental basis for the development and application of environmental friendly battery materials.

Perspective: Transcriptomics of Cryopreserved Cells

Cryopreservation is a well-known strategy to conserve genetic resources at ultra-low temperature. However, there is still limited knowledge on the cellular processes and molecular adjustments that allow cells to withstand the multiple stresses to which they are exposed during cryopreservation. To evaluate these processes, transcriptomics, the sub-discipline of omics that simultaneously examines mRNA transcripts formed by transcription from the genome, has been recently used. This article reviews recent scientific studies which use the basic principles of cryopreservation practices together with transcriptomics approaches, within the conceptual framework of cryobiomics. Moreover, the connections between factors that may be useful to optimize and validate approaches for mammalian or plant cell cryopreservation are also assessed. Transcriptomic applications are mainly performed with methods such as reverse transcriptase polymerase chain reaction (RT-PCR), simultaneous polymerase chain reaction (real-time PCR), northern blot, microarray/biochip and gene expression analysis (SAGE). Transcriptomic technologies allow a global view of gene expression profiles of different mammalian or plant cell types to be obtained before and after cryopreservation under multiple stress conditions. For these processes, small amounts of RNA enable efficient transcriptomics analysis. Transcriptomic analysis of cryopreserved mammalian and plant cells provides a conceptual way to identify the genes and their relative alterations in transcriptional abundances together with non-coding RNAs involved in important pathways related to cell viability and proliferation during and after cryopreservation. Moreover, it greatly contributes to understanding of non-fatal cryodamage and related developmental disorders in cryopreserved mammalian oocytes and sperm. In addition, single cell transcriptomics has the potential to non-invasely monitor immune actions and to diagnose the stage of the inflammatory process in kidney. Finally, qRT-PCR and RNA-seq studies have also revealed that some transcription factors are effective at inducing cold tolerance in many plants by elevating the levels of soluble sugars, proline and unsaturated fatty acids in cells. Hence transcriptomics studies may also aid investigations of the main mechanisms behind the so-called 'cryo-recalcitrance' that is observed mostly in plant cells.

Genome-wide identification of shaker K+ channel gene family in sugar beet (Beta vulgaris L.) and function of BvSKOR in response to salt and drought stresses

Potassium (K+) is the most abundant cation in plants, which is absorbed by roots and distributed throughout the plants and within plant cells, and is involved in various cellular processes. Shaker K+ channel plays crucial roles in the absorption and distribution of K+ and in the response to abiotic stress in plants. Herein, a total of six shaker K+ channel genes, BvKAT1, BvKAT3, BvAKT1, BvAKT2, BvAKT5, and BvSKOR, were identified in the genome of sugar beet (Beta vulgaris L.). The coding domain sequences (CDS) of these genes ranged from 2232 to 2739bp, and protein lengths were varied from 743 to 912 aa. The shaker K+ channel genes contained hormone-related and light responsiveness cis-acting regulatory elements. The phylogenetic analysis showed that BvSKOR was highly conserved and contained six transmembrane structures. The expression patterns of BvSKOR under salt and osmotic stress were analyzed by qRT-PCR, and found that the expression level of BvSKOR under low concentration salt and osmotic stress at short period of treatment were significantly higher than that of the control group. The function of BvSKOR was further verified in tobacco (Nicotiana tabacum), and the results showed that under salt and osmotic stress, the roots of transgenic plants were significantly stronger than those of wild type (WT) plants, and the relative water content (RWC), chlorophyll, proline, soluble sugar, soluble proteins contents and antioxidant enzyme activity were significantly higher than those of WT plants. These results indicated that overexpression of BvSKOR can significantly enhance the salt and drought tolerance in transgenic tobacco plants. This study could provide theoretical support and genetic resources for genetic improvement of crops stress resistance.

Role of biosynthesized silver nanoparticles in mitigating hyperhydricity in micropropagated watermelon (Citrullus lanatus Thunb.) and assessment of genetic fidelity using RAPD and SCoT markers

Watermelon (Citrullus lanatus) is one of the five most consumed fresh fruits and is a commercially important horticulture crop. The consumer demand for seedless watermelons has considerably increased due to their superior taste and ease of consumption. Seedless watermelon plants are triploids hence plant tissue culture technology which is the cultivation of plant cells, tissues, or organs on specially formulated nutrient media can facilitate the rapid multiplication of seedless watermelon varieties. However, hyperhydricity has been reported as a frequent problem for in vitro growth and development of watermelon. Hence, the present study highlights the application of silver nanoparticles biosynthesized from Parthenium hysterophorus (PHAgNPs) for reversal of hyperhydricity and enhancing in vitro shoot production in watermelon. The biosynthesized PHAgNPs was characterized using UV–vis spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction analysis and Transmission electron microscopy. Cotyledonary nodes used as explant and cultured in three types of cytokinins (BAP, TDZ and KIN) became hyperhydric, losing their ability to regenerate at high cytokinin concentrations (> 1.5 mg/L) irrespective of the cytokinin type. The optimum concentration of BAP (1.0 mg/L) fortified with PHAgNPs (15.0 mg/L) exhibited an improved response of 91 % and induced a maximum of 32.33 shoots with a maximum shoot length of 5.66 cm after 6 weeks. The incorporation of PHAgNPs reduced the percentage of hyperhydricity from 29 % to 1.33 % in regenerated shoots, which was confirmed by the reduction in relative water content (RWC) from 93.33 % to 80.33. Silver ions reduced H2O2 content by 50 % and increased photosynthetic pigments (chlorophyll a, b and carotenoids) by 50 %, which contributed to the formation of healthy regenerated shoots, with opened stomata compared to closed in hyperhydric shoots. Compared with those of hyperhydric shoots, the gene expression patterns of 1-aminocyclopropane-1-carboxylase synthase (ACS1) and 1-aminocyclopropane-1-carboxylic acid oxidase (ACO1) decreased after the retroversion of shoots to 15 mg/L PHAgNP medium. The relative gene expression profiles of ACS1 and ACO1 in hyperhydric shoots were 8.8- and 1.8-fold greater than those in normal shoots, respectively. Profuse root growth was observed in MS basal media supplemented with IBA (1.0 mg/L) and PHAgNPs (10.0 mg/L), which resulted in the greatest number of roots (12.33), with an average root length of 4.33 cm and a response of 89.33 %. The genotoxic effect of PHAgNPs evaluated using RAPD and SCoT molecular markers, showed that the addition of low levels of silver nanoparticles to the medium did not cause any genetic variation. The efficient regeneration protocol standardized in this study provides a solution to solve the problem of hyperhydricity in watermelon regeneration.

Plant plasmodesmata bridges form through ER-dependent incomplete cytokinesis.

Diverging from conventional cell division models, plant cells undergo incomplete division to generate plasmodesmata communication bridges between daughter cells. Although fundamental for plant multicellularity, the molecular events leading to bridge stabilization, as opposed to severing, remain unknown. Using electron tomography, we mapped the transition from cell plate fenestrae to plasmodesmata. We show that the endoplasmic reticulum (ER) connects daughter cells across fenestrae, and as the cell plate matures, fenestrae contract, causing the plasma membrane (PM) to mold around constricted ER tubes. The ER's presence prevents fenestrae fusion, forming plasmodesmata, whereas its absence results in closure. The ER-PM protein tethers MCTP3, MCTP4, and MCTP6 further stabilize nascent plasmodesmata during fenestrae contraction. Genetic deletion in Arabidopsis reduces plasmodesmata formation. Our findings reveal how plants undergo incomplete division to promote intercellular communication.

Study on 13C MultiCP/MAS ssNMR Analysis of Tobacco Pectin

Background: As one of the most important economic crops, tobacco products have a long history and dominate the development of the world economy. Pectin, as a complex colloidal substance widely present in plant cell walls, its content is an important factor affecting the safety of tobacco smoking. Objective: This study aimed to analyze the content and structure of pectin in tobacco samples Methods: In this study, tobacco pectin was extracted by ultrasonic-assisted ionic liquid extraction, and the 13C MultiCP/MAS NMR spectral analysis of pectin was conducted. Results: The type of extractant, duration of ultrasonication, extraction temperature, and solid-liquid ratio were optimized. Under the conditions of using 1-Butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4) as the extractant, the solid-liquid ratio of 1:20 g/mL, and the ultrasonic power of 600 w for 30 min at 30°C, the yield of 23.7% of tobacco stem pectin and the purity of 54.2% could be obtained. The optimized MultiCP sequence parameters, with 10 CP cycles of 1.0 ms and the repolarization time of 50 ms could obtain high-resolution spectra within a time of 1.0 h. The C-6 peaks of the pectin in spectra were fitted using the spectral deconvolution technique and calculated the methylesterification (DM) of the tobacco pectin, which was generally less than 50% and belonged to the low methyl esterification pectin. The pectin content of the tobacco sample was calculated using the standard curve method with the addition of dimethyl sulfone (DMS) as an internal reference. The results of this method were consistent with the colorimetric method. Conclusion: The 13C MultiCP/MAS NMR method has the advantages of being green, fast, and accurate and provides a new technical tool for quantitative and qualitative studies of cell wall substances in tobacco samples.

Whole-pathway stimulation of anthocyanin biosynthesis by UDP-glycose: flavonoid glycosyltransferase gene (UFGT) providing new insights into natural product development based on plant cell factory

Whole-pathway stimulation of anthocyanin biosynthesis by UDP-glycose: flavonoid glycosyltransferase gene (UFGT) providing new insights into natural product development based on plant cell factory

A cytoplasmic osmosensing mechanism mediated by molecular crowding-sensitive DCP5.

Plants are frequently challenged by osmotic stresses. How plant cells sense environmental osmolarity changes is not fully understood. We report that Arabidopsis Decapping 5 (DCP5) functions as a multifunctional cytoplasmic osmosensor that senses and responds to extracellular hyperosmolarity. DCP5 harbors a plant-specific intramolecular crowding sensor (ICS) that undergoes conformational change and drives phase separation in response to osmotically intensified molecular crowding. Upon hyperosmolarity exposure, DCP5 rapidly and reversibly assembles to DCP5-enriched osmotic stress granules (DOSGs), which sequestrate plenty of mRNA and regulatory proteins, and thus adaptively reprograms both the translatome and transcriptome to facilitate plant osmotic stress adaptation. Our findings uncover a cytoplasmic osmosensing mechanism mediated by DCP5 with plant-specific molecular crowding sensitivity and suggest a stress sensory function for hyperosmotically induced stress granules.

Host Recognition for Survival of Plant Pathogens

The intact, healthy plant is a community of cells built in a fortress-like fashion. Plant cells consist of cell wall contains the nucleus and various organelles and all the substances for which the pathogens attack them. The cytoplasm and the organelles it contains are separated from each other by membranes that carry various types of proteins embedded in them (Fig. 5-2). The plant surfaces that come in contact with the environment either consist of cellulose, as in the epidermal cells of roots and in the intercellular spaces of leaf parenchyma cells, or consist of a cuticle that covers the epidermal cell walls, as is the case in the aerial parts of plants. Often an additional layer, consisting of waxes, is deposited outside the cuticle, especially on younger parts of plants Pathogens attack plants because during their evolutionary development they have acquired the ability to live off the substances manufactured by the host plants, and some of the pathogens depend on these substances for survival. Many substances are contained in the protoplast of the plant cells, however, and if pathogens are to gain access to them they must first penetrate the outer barriers formed by the cuticle and/or cell walls. Even after the outer cell wall has been penetrated, further invasion of the plant by the pathogen necessitates the penetration of more cell walls. Furthermore, the plant cell contents are not always found in forms immediately utilizable by the pathogen and must be broken down to units that the pathogen can absorb and assimilate. Moreover, the plant, reacting to the presence and activities of the pathogen, produces structures and chemical substances that interfere with the advance or the existence of the pathogen; if the pathogen is to survive and to continue living off the plant, it must be able to overcome such obstacles. Therefore, for a pathogen to infect a plant it must be able to make its way into and through the plant, obtain nutrients from the plant, and neutral

The Role of the Swollen State in Cell Proliferation.

Cell swelling is known to be involved in various stages of the growth of plant cells and microorganisms but in mammalian cells how crucial a swollen state is for determining the fate of the cellular proliferation remains unclear. Recent evidence has increased our understanding of how the loss of the cell surface interactions with the extracellular matrix at early mitosis decreases the membrane tension triggering curvature changes in the plasma membrane and the activation of the sodium/hydrogen (Na +/H +) exchanger (NHE1) that drives osmotic swelling. Such a swollen state is temporary, but it is critical to alter essential membrane biophysical parameters that are required to activate Ca2 + channels and modulate the opening of K + channels involved in setting the membrane potential. A decreased membrane potential across the mitotic cell membrane enhances the clustering of Ras proteins involved in the Ca2 + and cytoskeleton-driven events that lead to cell rounding. Changes in the external mechanical and osmotic forces also have an impact on the lipid composition of the plasma membrane during mitosis.