Stress stimulation induced resistance of plant

During the course of pathogens penetrating the plant cell, besides of chemical secretion, the pathogens may cause mechanical signal by the physical pressure on the plant cell. In the current study, we took the stress as the mechanical signal elicitor to find the effect of plant resistance induced by stress. The results showed that an appropriate stress stimulation can evidently improve the plant resistance. However, disruption the plasma membrane–cell wall adhesion will absolutely eliminate this kind of inducement effect, which suggests that the plant resistance inducement by stress depend on the adhesion of plasma membrane–cell wall. Also we found that stress stimulation may cause synthesis of lignin and increase the activity of phenylalaninc ammonial lyase (PAL) chitinase and β-1,3-glucanase obviously. The results showed that stress stimulation may not only enhance ability of the plant cell resistant to pathogen penetration but also elicit the accumulation of pathogens suppression or antimicrobial chemical substance in the plant cell.     

The accumulation of phytoalexin in cucumber plant after stress

During the course of pathogens penetrating the plant cell, besides of chemical secretion, the pathogens may cause mechanical signal by the physical pressure on the plant cell. In the current study, we use the pressure as the stress signal to study the induction in plant resistance and the effect of accumulation of phytoalexin. We found that stress can induce the resistance in cucumber seeding significantly. Peptides contained RGD motif can specific block the adhesion between plant cell wall and plasma membrane. When breaking the plant cell wall and plasma membrane by using RGD peptides, the stress induction effect is almost absolutely eliminated. The results of assay with TLC and HPLC showed that stress stimulation could increase the accumulation of cucumber seeding phytoalexin. So, we can conclude that the accumulation of phytoalexin is one possible reason of improve the stress induced resistance. When block the adhesion between plant cell wall and plasma membrane by RGD, there are only part of accumulation of phytoalexin. The results suggest that stress induced resistance and accumulation of phytoalexin of plant is required for the adhesion of plant cell wall–plasma membrane.     

Preliminary study on phytoalexin induction in cucumber

Inducer can induce new active composition and increase the content of the active composition in the plant. In this paper, we investigated the synthesis and accumulation of phytoalexin in cucumber seedlings which were induced by chemical inducer of the salicylic acid (SA) and physical inducer. Analyzed by experiment of antifungal activity, thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC), the result was that both SA and stress can induce the synthesis and accumulation of phytoalexin in cucumber seedlings. But the content of phytoalexin induced by SA was lower than it induced by stress. And in this paper, another conclusion was that the transduction of physical signal and the chemical signal in the plant depended on the adhesion between cell wall and plasma and active oxidative species producted by stimulation.     

Stress stimulus induced resistance to Cladosporium cucumerinum in cucumber seeding

Up to date, the studies of plant induced resistance have become the focus in plant pathology and physiology. During the course of pathogens penetrating the plant cell, besides of chemical secretion, the pathogens may generate mechanical signal caused by the physical pressure on the plant cell. In the non-host resistance, both the chemical signal and the mechanical stress signal are considered to have contribution to the entire defense reaction acted by the plant. The penetration of pathogen Cladosporium cucumerinum to cucumber is thought to be one of the model in research of plant induced resistance. In the current study, as a mechanical signal elicitor, the appropriate stress stimulus was proved to effectually induce the resistance of cucumber seedling to C. cucumerinum. After the treatment of the stress stimulus on leaves, the activities of resistance-related enzymes were significantly increased, such as phenylanine ammonia lyase (PAL), peroxidase (POD). Also, we found that stress stimulation may cause synthesis of lignin, which acts as the physical barrier to defense the pathogens. The results suggest that stress stimulation may not only enhance ability of the plant cell resistance to pathogen penetration but also elicit the accumulation of pathogens suppression or antimicrobial chemical substance in the plant cell.     

Plant cell walls: supramolecular assembly, signalling and stress

The structure of the primary cell wall in non-graminaceous plants is briefly reviewed and its role in providing mechanical strength to the plant and protecting it from microbial infection are described. A variety of signalling mechanisms involve oligosaccharides released by glycanase enzymes from microbial pathogens, and some of the mechanisms may be implicated in the regulation of metabolism in ripening fruits. There is some evidence that cell walls are able to sense damage or loss of integrity and that signals can accordingly be passed back to the cytoplasm. Primary cell walls must combine the mechanical and other functions with the capacity to grow in a controlled way. A modification of the ‘Molecular Velcro’ model developed originally to describe deformation of wood is used to predict load-deformation curves like those described by the Lockhart equation for the relationship between turgor stress and growth. Predicting a stress threshold for growth does not require the assumption of enzyme activity, although in fact enzyme activity is indeed required to permit growth at the rates normally observed.     

Effect of shear stress on adhering polyelectrolyte capsules

A parallel plate flow chamber was implemented to study the deformation and adhesion of individual spherical hollow polyelectrolyte multilayered shells adhering to a coated surface. The device provides a well-defined laminar flow allowing the determination of the shear stress to which the capsules are being exposed up to 15 N/m(2). The results of the investigations indicate a strong dependence of the adhesion and mechanical resistance on the capsule size and wall thickness. Thin walled capsules, constituted of 8 polyelectrolyte layers (thickness congruent with 12 nm), are immediately deformed when exposed to flow while thick capsules, constituted of 16 layers (thickness congruent with 24 nm), of equal dimensions are detached from the surface for drag forces below 50 nN. It was observed that adhering capsules exposed to flow undergo an increase in their adhesion area in the direction of flow, resulting in rolling of the capsules. It was also found that the resistance of the capsules decreases after acetone treatment, indicating a weakening of the polyelectrolyte multilayer structure in the presence of this solvent.     

Non-thermal Plasma Induced Expression of Heat Shock Factor A4A and Improved Wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) Growth and Resistance Against Salt Stress

There is a huge interest in making and applying innovating functional devices based on basic sciences (like physics) to improve plant growth and resistance against various stress conditions. This research was carried out in order to investigate effects of cold plasma on expressions of heat shock factor A4A (HSFA4A), plant growth and post reactions to salt stress. Wheat seedlings were treated with plasma (0.84 W/cm² surface power densities) at different exposure times. In both three and 6 h after plasma, inductions in expressions of HSFA4A were recorded in roots, compared to control. Six hours after treatments, plasma-induced the shoot expressions of HSFA4A in the treated seedlings, contrasted to 3 h. Plasma treatment caused not the only enhancement in shoot fresh and dry mass and total leaf area, but also alleviated adverse impacts of salinity. Destroying impacts of salinity on chlorophyll contents were mitigated by plasma. Peroxidase activity was decreased by 27% for salinity treatment alone over control, while it was increased by 15% for plasma and salinity-treated samples, compared to salinity control. The highest activities of phenylalanine ammonia lyase (PAL) were found in plasma treatment alone. PAL activity was found to be higher in plasma-pretreated seedlings counteracted to salt stress, relative to the salinity control. The plasma treatment may act as an effective elicitor to modify gene expression, thereby improving plant growth and resistance. Plasma technology should be considered as a new functional technology in plant sciences.     

The role of microstructure on the mechanical properties of polyurethane foams containing thermoregulating microcapsules

Rigid polyurethane foams with up to 50 wt% of microcapsules from LDPE-EVA containing Rubitherm^®RT27 were synthesized. The influence of microcapsules on the foams density, microstructure and mechanical resistance was studied. Cell size and strut and wall thicknesses were analyzed by SEM. The relationships between densities and foam microstructures with their Young's moduli and collapse stress were found by the Gibson and Ashby formulations and the Kerner equation for mechanical properties of composites. It was found a cell structure change from polyhedral closed-cells to spherical or amorphous open-cells. A good agreement between the experimental and theoretical data was observed but requiring a cell form factor. Thus, Fitting parameters confirmed the high trend of these microcapsules to be incorporated into the foam cell walls and the form factors depicted the abrupt change of cell morphology. Thus, these equations are suitable for predicting the mechanical properties of foams containing fillers of low mechanical resistance.     

Dynamic adhesion due to fluid infusion

The resistance of fluid infusion inside a thin film that separates an opening gap leads to viscous adhesion. Viscous adhesion can be detrimental for some mechanical devices such as valves or during additive manufacturing processes. On the other hand, it is also a mechanism found in nature for dynamic reversible adhesion. In this article we review analysis and measurements of viscous adhesion. In particular, we give conditions where viscous adhesion dominates over other surface forces. We also describe how characteristics of the solid surfaces such as roughness and elasticity, as well as the compliance of the load cell can be incorporated in the analysis. Finally, we discuss the knowledge gaps and scientific areas where a better understanding of viscous adhesion could be beneficial.     

Structural Features of the Algal Cell Determine Adhesion Behavior at a Charged Interface

We aimed to examine the effects of algal structural features on adhesion at a charged interface. Results showed that algae with a glycocalyx, and with a cellulose amphiesma adhered at a charged interface at species-specific potential ranges. Algae, encased with a calcite-encrusted theca, and with an organosilicate cell wall, did not adhere to the interface. These differences in the amperometrically determined adhesion behavior of algal cells are in agreement with reported cell mechanical properties. Critical interfacial tensions of adhesion show differences between the studied soft algal cells as a consequence of their distinct cell barrier structure, composition, and properties.     

A Glycan Array-Based Assay for the Identification and Characterization of Plant Glycosyltransferases

Growing plants with modified cell wall compositions is a promising strategy to improve resistance to pathogens, increase biomass digestibility, and tune other important properties. In order to alter biomass architecture, a detailed knowledge of cell wall structure and biosynthesis is a prerequisite. We report here a glycan array-based assay for the high-throughput identification and characterization of plant cell wall biosynthetic glycosyltransferases (GTs). We demonstrate that different heterologously expressed galactosyl-, fucosyl-, and xylosyltransferases can transfer azido-functionalized sugar nucleotide donors to selected synthetic plant cell wall oligosaccharides on the array and that the transferred monosaccharides can be visualized “on chip” by a 1,3-dipolar cycloaddition reaction with an alkynyl-modified dye. The opportunity to simultaneously screen thousands of combinations of putative GTs, nucleotide sugar donors, and oligosaccharide acceptors will dramatically accelerate plant cell wall biosynthesis research.     

Adhesion behaviors of human trophoblast cells by contact with endothelial cells

Although it is still not clear whether migratory trophoblasts reach the spiral arteries by migration within blood vessels against blood flow or by a mechanism of directional cell division/proliferation, this process involves the attachment and adhesion of trophoblasts to endothelial cells lining the blood vessel walls. This raises the possibility that the cell–cell contact with endothelial cells may regulate trophoblast cell adhesion behaviors according to the surrounding flow condition. To test this, the adhesion forces of early gestation human trophoblast cells (TCs) cultured on glass slides coated with type I rat collagen or cultured with human umbilical vein endothelial cells (HUVECs) were measured quantitatively using a micropipette aspiration technique. Then, the resistance of TCs co-cultured with HUVECs to flow-induced shear stress was assessed with a flow chamber technique. The results showed that the adhesion force of TCs to glass slides coated with collagen was positively correlated with the concentration of collagen. By contact with endothelial cells, the adhesion force and the resistance to shear stress for the TCs were significantly enhanced. The interdiction of integrin β1 interaction remarkably reduced the adhesion forces of TCs to endothelial cells, hence their resistance to shear stress. The results therefore suggest that the contacts of TCs with endothelial cells enhance the adhesion forces of human TCs, partially by regulating with the integrin β1 according to the flow condition (i.e., the shear stress) in such a way to prevent the TCs from being carried downstream by flowing blood.     

Integrated lithographic membranes and surface adhesion chemistry for three-dimensional cellular stimulation

The complex spatiotemporal organization of cellular and molecular interactions dictates the physiological function of cells. These behaviors are indications of an integrated response to a three-dimensional cellular environment and anchored in cell adhesion on scaffolds. Here, we are able to control interconnected structural, mechanical, and chemical stimuli by dictating the cellular environment through chemical surface modifications, soft lithography, and mechanical deformation. Control of these variables is obtained through the use of an elastomeric membrane chemically modified for cell adhesion with a pressure-driven cell-stretching device which creates a pattern of forces similar to those encountered in physiological environments. Further, the integration of lithographic methods and chemical patterning allows the introduction of space- and time-dependent parameters by combining mechanical stimulation, biochemical regulation, and scaffolding design. The method is applied to stimulate single cells and cell populations to examine cellular response with spatiotemporal control. This research provides the capacity to probe biological patterns and tissue formation under the influence of mechanical stress.     

A Glycan Array‐Based Assay for the Identification and Characterization of Plant Glycosyltransferases

Growing plants with modified cell wall compositions is a promising strategy to improve resistance to pathogens, increase biomass digestibility, and tune other important properties. In order to alter biomass architecture, a detailed knowledge of cell wall structure and biosynthesis is a prerequisite. We report here a glycan array‐based assay for the high‐throughput identification and characterization of plant cell wall biosynthetic glycosyltransferases (GTs). We demonstrate that different heterologously expressed galactosyl‐, fucosyl‐, and xylosyltransferases can transfer azido‐functionalized sugar nucleotide donors to selected synthetic plant cell wall oligosaccharides on the array and that the transferred monosaccharides can be visualized “on chip” by a 1,3‐dipolar cycloaddition reaction with an alkynyl‐modified dye. The opportunity to simultaneously screen thousands of combinations of putative GTs, nucleotide sugar donors, and oligosaccharide acceptors will dramatically accelerate plant cell wall biosynthesis research.     

超微电极实时监测植物细胞壁参与调控的单细胞活性氧爆发

植物细胞活性氧爆发在植物的抗病以及信号转导中起着非常重要的作用,植物内活性氧产生及代谢受到复杂而精确的机制调控,从而维持正常的活性氧水平以发挥其生理功能. 然而,在单细胞水平开展活性氧爆发实时监测及其调控机制研究一直受到很大的挑战. 本文以碳纤维微盘电极（CFMDE）为基底电极,利用Nafion的模板效应,采用电化学沉积法制得纳米铂颗粒修饰电极（NPt/Nafion/ CFMDE）;同时采用基于聚二甲基硅氧烷（PDMS）的软光刻技术,制备了一种高效固定植物悬浮细胞的琼脂糖阵列微孔芯片. 使用NPt/Nafion/CFMDE实时监测了单个拟南芥原生质体活性氧爆发,并证明电化学监测活性氧的主要成分为过氧化氢. 在此基础上,采用浅层培养法培养原生质体再生植物细胞壁. 电化学监测结果表明,与单个原生质体相比,植物细胞在受到刺激时释放的过氧化氢量显著降低;然而当采用过氧化物酶抑制剂抑制植物细胞壁上过氧化物酶活性后,植物细胞释放过氧化氢量显著回升. 研究结果表明细胞壁在活性氧爆发过程具有很好的调控功能,可望促进植物细胞活性氧爆发及其调控机制的研究.     

High‐Frequency Mechanostimulation of Cell Adhesion

Cell adhesion is regulated by molecularly defined protein interactions and by mechanical forces, which can activate a dynamic restructuring of adhesion sites. Previous attempts to explore the response of cell adhesion to forces have been limited to applying mechanical stimuli that involve the cytoskeleton. In contrast, we here apply a new, oscillatory type of stimulus through push–pull azobenzenes. Push–pull azobenzenes perform a high‐frequency, molecular oscillation upon irradiation with visible light that has frequently been applied in polymer surface relief grating. We here use these oscillations to address single adhesion receptors. The effect of molecular oscillatory forces on cell adhesion has been analyzed using single‐cell force spectroscopy and gene expression studies. Our experiments demonstrate a reinforcement of cell adhesion as well as upregulated expression levels of adhesion‐associated genes as a result of the nanoscale “tickling” of integrins. This novel type of mechanical stimulus provides a previously unprecedented molecular control of cellular mechanosensing.     

Cell and protein compatibility of parylene-C surfaces

Parylene-C, which is traditionally used to coat implantable devices, has emerged as a promising material to generate miniaturized devices due to its unique mechanical properties and inertness. In this paper we compared the surface properties and cell and protein compatibility of parylene-C relative to other commonly used BioMEMS materials. We evaluated the surface hydrophobicity and roughness of parylene-C and compared these results to those of tissue culture-treated polystyrene, poly(dimethylsiloxane) (PDMS), and glass. We also treated parylene-C and PDMS with air plasma, and coated the surfaces with fibronectin to demonstrate that biochemical treatments modify the surface properties of parylene-C. Although plasma treatment caused both parylene-C and PDMS to become hydrophilic, only parylene-C substrates retained their hydrophilic properties over time. Furthermore, parylene-C substrates display a higher degree of nanoscale surface roughness (>20 nm) than the other substrates. We also examined the level of BSA and IgG protein adsorption on various surfaces and found that surface plasma treatment decreased the degree of protein adsorption on both PDMS and parylene-C substrates. After testing the degree of cell adhesion and spreading of two mammalian cell types, NIH-3T3 fibroblasts and AML-12 hepatocytes, we found that the adhesion of both cell types to surface-treated parylene-C variants were comparable to standard tissue culture substrates, such as polystyrene. Overall, these results indicate that parylene-C, along with its surface-treated variants, could potentially be a useful material for fabricating cell-based microdevices.     

Enhanced In situ Activity of Peroxidases and Lignification of Root Tissues after Exposure to Non-Thermal Plasma Increases the Resistance of Pea Seedlings

Improving the germination of economically important crops and the condition of young plants is a major challenge currently facing agricultural practice. Pea (Pisum sativum L.) is one of the four most important cultivated legumes, along with groundnut (Arachis hypogaea L.), soybean (Glycine max L.) and beans (Phaseolus vulgaris L.). Due to the high protein content (23–33%), there is an interest in growing this crop as a source of protein for humans and animals. In this study, we focused on the effect of Cold Atmospheric Pressure Plasma (CAPP) on the decontamination and germination of pea seeds, on young seedling growth and production parameters, and on increasing their resistance and mechanical strength. We can state that germination increased by 10 to 25% after plasma treatment, and the most significant decontamination effect was detected when using non-thermal plasma generated in the ambient air (A-variants) and in the nitrogen atmosphere (N-variants). The increased in situ activity of peroxidases (POX) in the cell walls of A-variants and N-variants is also closely related to the increase in the mechanical strength of the cell walls and thus contributes to the higher resistance of these seedlings. This is also illustrated by the differences in lignin deposition among the different variants after CAPP treatment. To our knowledge, this is the first study concerning the influence of CAPP on the lignification of root tissues and on increasing the strength and resistance of plants.

     

Introductory remarks

Separate terms to distinguish the matrix between the cells that grow in vitro and the matrix that separates and surrounds cells in the living body are being proposed. The currently used designations: pericellular, extracellular, or intercellular matrix should be used only for the substance produced by cells in vitro (cultures). The well organized, highly specific, and stable structure with significant topographic variations between the cells of living tissues and organs should be called biological matrix or briefly as biomatrix. My experiments published in the early 1940s on plant cell walls illustrate some similarities between biomatrix of animal tissues and plant cell wall. When cells of plant epithelial membranes undergo plasmolysis, the space between the contracting cell and cellulose cell wall is filled with filaments called Hechtian filaments or strands. With silver impregnation, these filaments become a fibrous network, filling the space between the cell wall and the contracting plasma (cell) membrane. A similar extracellular fibrous network has been described earlier after silver impregnation in some animal tissues. I interpreted my finding that a pectin-like polysaccharide in the cell wall biomatrix and hyaluronan, the only polysaccharide present in the biomatrix of animal tissues, are responsible for this fibrous network artifact.     

Effects of intermediate Ar plasma treatments on CrN coating microstructures and property evolutions

Chromium nitride (CrN) coatings with different steps of intermediate argon plasma treatments were deposited with primary (200) orientation by multi‐arc ion plating technique. By virtue of scanning electron microscopy, X‐ray diffraction and high‐resolution transmission electron microscopy, the influence of intermediate argon plasma treatments on the coating microstructures, mechanical properties and corrosion properties as well as tribological behaviors in artificial seawater solutions were systematically investigated. It was assumed that the mechanical properties, adhesion strength, corrosion and tribological performances of coatings depended on argon plasma treatment steps. High‐performance coatings could be obtained by proper plasma treatment steps. The superior anti‐corrosion ability of coating with appropriate treatment steps may be ascribed to the increased charge transfer resistance due to alternative interface and CrN layer and the compact microstructure. On the other hand, the excellent tribological performances in seawater conditions may be attributed to the enhanced mechanical properties. Otherwise, further increase in treatment steps was assumed to distinctly increase defects and deteriorate the coating integrity thus weakening coating properties and behaviors. Copyright © 2016 John Wiley & Sons, Ltd.