Sensing of gene expression in live cells using electrical impedance spectroscopy and DNA-functionalized gold nanoparticles

A novel electrical impedance spectroscopy-based method for non-destructive sensing of gene expression in living cells is presented. The approach used takes advantage of the robustness and responsiveness of electrical impedance spectroscopy and the highly specific and selective nature of DNA hybridization. The technique uses electrical impedance spectroscopy and gold nanoparticles functionalized with single-stranded DNA complementary to an mRNA of interest to provide reliable, real-time, and quantifiable data on gene expression in live cells. The system was validated by demonstrating specific detection of the uidA mRNA, which codes for the β-glucuronidase (GUS) enzyme, in Solanum lycopersicum MsK8 cells. Gold nanoparticles were functionalized with single-stranded DNA oligonucleotides consisting of either a sequence complementary to uidA mRNA or an arbitrary sequence. The DNA-functionalized gold nanoparticles were mixed with cell suspensions, allowing the gold nanoparticles to penetrate into the cells. The impedance spectra of suspensions of cells with gold nanoparticles inserted within them were then studied. In suspensions of uidA-expressing cells and gold nanoparticles functionalized with the complementary single-stranded DNA oligonucleotide, the impedance magnitude in the frequency range of interest was significantly higher (146 %) in comparison to all other controls. Due to its highly selective nature, the methodology has the potential to be used as a precision agricultural sensing system for accurate and real-time detection of markers of stress, viral infection, disease, and normal physiological activities.

Protoplast Isolation, Culture, and Regeneration in Common and Tartary Buckwheat

Techniques based on the use of plant protoplasts are a convenient model for better understanding and observing developmental changes in the cells. The establishment of research tools based on protoplasts consists of many steps needed for optimization. Here, we describe the culture of morphogenic callus (MC)- and hypocotyl-derived protoplasts of common (Fagopyrum esculentum Moench) and Tartary (F. tataricum (L.) Gaertn.) buckwheat. Protoplasts embedding in agarose matrix and application of plant hormones, including phytosulfokine (PSK), enable the development of protoplast cultures and plant regeneration.

Regulation of Molecular Farming Products

The regulation of molecular farming is a complex topic because plants and plant-based systems are relative newcomers among the many production platforms available for recombinant proteins. The regulations specific for different types of product (human/veterinary pharmaceuticals and medical devices, cosmetics, diagnostics, and research reagents) must therefore be overlaid with the regulations governing hitherto unfamiliar production platforms, and this must be achieved in different jurisdictions that handle genetically modified organisms (and genetically modified plants in particular) in very different ways. This chapter uses examples of different product types and production methods in three different jurisdictions (the USA, the EU, and Canada) to demonstrate some of the challenges facing the regulatory authorities.

Isolation of Specialized Plant Cells by Fluorescence-Activated Cell Sorting

Plant organs are built of different cell types, characterized by specific transcription programs and metabolic profiles. The possibility of isolation of such cell types to perform differential transcriptomic, proteomic and metabolomic analyses is highly important to understand many aspects of plant physiology, namely, the structure and regulation of economically valuable specialized metabolic pathways. Here, we describe the isolation of idioblast leaf protoplasts of the medicinal plant Catharanthus roseus by fluorescence-activated cell sorting, taking advantage of the differential autofluorescence properties of those specialized cells.

Curium(III) and europium(III) as luminescence probes for plant cell (Brassica napus) interactions with potentially toxic metals

We have investigated the interaction of the actinide Cm(III) and its lanthanide homologue Eu(III) with cells of Brassica napus in suspension. This study combines biochemical techniques (plant cell response) with spectroscopic experiments to determine the chemical speciation of hazardous metals in contact with the plant cells. Experiments conducted over a period of 7 d showed that B. napus cells were able to bioassociate both potentially toxic metals in significant amounts up to 0.58 µmol Eu/g_{fresh cells} and 1.82 µmol Cm/g_{fresh cells} at 30 µM Eu(III) and 0.68 µM Cm(III), respectively. For Cm(III), a biosorption process could be identified as soon as 5 h post-exposure with 73 ± 4% of the Cm(III) bioassociated. Luminescence spectroscopy results based on UV and site-selective excitation confirmed the existence of three Cm(III)/Eu(III) [M(III)] species in both the supernatants and cells. The findings detailed herein support that M(III) coordinates to two kinds of carboxyl groups and phosphate groups.

Quantum information teleportation through biological wires, gravitational micro-bio-holes and holographic micro-bio-systems: A hypothesis

Biological systems like cells, bacteria, chloroplasts and other micro-organisms could exchange quantum particles like electrons, photons and gravitational waves and have large distant information teleportation. This is because that their DNAs and membranes are formed from quantum particles like electrons and protons and by their motions, some currents and waves are emerged. These waves have the main role in information teleportation. There are different methods which could be used for quantum information teleportation in biological system. Some of these mechanisms are: 1. Microbes, micro-bubbles and some other biological molecules like to form some biological lines specially near the cellular gates. Also, some biological lines may be formed between two cells. These biological lines could play the role of wires which transmit information from a place to another one. For example, some signatures of this quantum information teleportation could be seen in biological lines which are emerged near the plant cell walls or gates or close to chloroplasts. Chloroplasts shoot some spinors which maybe confined within the micro-bubbles or absorb by microbes. These bubbles and microbes may join to each other and form some biological lines which may be strengthen from a plant cell to another. These biological lines could be seen near the plant cell walls or on a metal which connects two parts of a leaf. 2. Some another signatures of “quantum photon exchange or quantum information teleportation” could be seen between microbes under the objective lenses and macro-objects on the eye lenses of a light microscope. It seems that as microscope make big images from microbes for us, produce small pictures of macro-objects for microbes such as they could diagnose them and interact with them. This property could be used in controlling microbes. 3. Another way for controlling microbes is using of virtual shapes which are induced by a special light source. For example, using a multi-gonal lamp, one can induce multi-gonal shape within the micro-bubbles. Also, this special lamp could force microbes and micro-bubbles to build multi-gonal colonies on a metal-glass slide. Maybe, by using this property, one can build a light source with the shape of anti-microbial matter and induce anti-microbial property within micro-bubbles. 4. Another main way for quantum teleportation is using of gravitational holes which may be emerged by increasing concentration of microbes and heavy cells in some points. These holes absorb microbes and micro-bubbles and conduct them to the heavy cells. Usually, there are some white holes near these dark holes which as a proposal, one can assume that these white holes are another end of gravitational holes and emit photons which are entered from dark end. 5. And finally, a very main mechanism for quantum information teleportation with microbes and controlling them is using of a holography and inducing virtual microbes and biological molecules in biological systems. For example, by a combinations of two lights with different colors under a light microscope in a dark room, one may induce some non-virtual microbes in biological systems such as each microbe interacts with a virtual microbe. This is because that light waves take photos of microbes, collide with lenses of microscopes and return to the slide and form virtual microbes or biological molecules. This technique could be used in curing diseases. Although, results of our experiments show the correctness of these mechanisms and theories, however, for the moment, we propose them only as a proposal and hypothesis and hope that other scientists do similar experiments. Also, some of our experiments may be at preliminary stages; however they could be used as a hypothesis, proposal and guidance.

Electrical impedance spectroscopy of plant cells in aqueous buffer media over a wide frequency range of 4 Hz to 20 GHz

Electrical impedance spectroscopy was performed on suspensions of plant cells in aqueous buffer media over a wide frequency range of 4 Hz to 20 GHz. Custom probes were designed, manufactured, and used for these investigations. Experiments were performed with a custom-made parallel plate probe and impedance analysers in the low-frequency range (4 Hz to 5 MHz), with a custom-made coaxial airline probe and a vector network analyser in the mid-frequency range (100 kHz to 3 GHz), and with a commercial open-ended probe and a vector network analyser in the high-frequency range (200 MHz to 20 GHz). The impedance data acquired were processed in order to eliminate the effects of parasitics and compensate for geometrical differences between the three probes. Following this, the data were fitted to a unified model consisting of the Randles and Debye models. The data were also normalized to a reference measurement, in order to accentuate the effects of cell concentration on the impedance of the suspensions.•

The methodology allows for impedance spectroscopy of cell suspensions over a wide frequency range spanning 10 orders of magnitude.

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It allows for compensation of parasitics and of geometrical variations between probes, using mathematical techniques

Green Light-Controlled Gene Switch for Mammalian and Plant Cells

The quest to engineer increasingly complex synthetic gene networks in mammalian and plant cells requires an ever-growing portfolio of orthogonal gene expression systems. To control gene expression, light is of particular interest due to high spatial and temporal resolution, ease of dosage and simplicity of administration, enabling increasingly sophisticated man-machine interfaces. However, the majority of applied optogenetic switches are crowded in the UVB, blue and red/far-red light parts of the optical spectrum, limiting the number of simultaneously applicable stimuli. This problem is even more pertinent in plant cells, in which UV-A/B, blue, and red light-responsive photoreceptors are already expressed endogenously. To alleviate these challenges, we developed a green light responsive gene switch, based on the light-sensitive bacterial transcription factor CarH from Thermus thermophilus and its cognate DNA operator sequence CarO. The switch is characterized by high reversibility, high transgene expression levels, and low leakiness, leading to up to 350-fold induction ratios in mammalian cells. In this chapter, we describe the essential steps to build functional components of the green light-regulated gene switch, followed by detailed protocols to quantify transgene expression over time in mammalian cells. In addition, we expand this protocol with a description of how the optogenetic switch can be implemented in protoplasts of A. thaliana.

Electrical Impedance Spectroscopy of plant cells in aqueous biological buffer solutions and their modelling using a unified electrical equivalent circuit over a wide frequency range: 4Hz to 20 GHz

A simple, ultra-wide frequency range, equivalent circuit for plant cell suspensions is presented. The model incorporates both the interfacial interactions of the suspension with the electrode, dominant at low frequencies, and the molecule and cell polarization mechanisms dominant at higher frequencies. Such model is useful for plant cell characterization allowing a single set of parameters over >9 orders of magnitude, whilst allows electronic simulations over the whole frequency range using a single model, simplifying the design of electronic systems of integrated plant cell sensors. The model has been experimentally validated in the frequency range of 4 Hz-20 GHz with each component in the circuit representing a physical phenomenon. Various cell concentrations (MSK8 tomato cells in Murashige and Skoog media) have been investigated, showing clear correlations of the cell capacitance increasing within the range of 200-600 pF, whilst cell resistance (R) decreasing within the range of approximately 0.8-3 kΩ within the cell concentration X-Y cells/mL range. This is the first model ever reported that covers such a wide frequency range and includes both interfacial and polarization effects in this simple form.

Plant cell (Brassica napus) response to europium(III) and uranium(VI) exposure

Experiments conducted over a period of 6 weeks using Brassica napus callus cells grown in vitro under Eu(III) or U(VI) stress showed that B. napus cells were able to bioassociate both potentially toxic metals (PTM), 628 nmol Eu/gfresh cells and 995 nmol U/gfresh cells. Most of the Eu(III) and U(VI) was found to be enriched in the cell wall fraction. Under high metal stress (200 μM), cells responded with reduced cell viability and growth. Subsequent speciation analyses using both metals as luminescence probes confirmed that B. napus callus cells provided multiple-binding environments for Eu(III) and U(VI). Moreover, two different inner-sphere Eu3+ species could be distinguished. For U(VI), a dominant binding by organic and/or inorganic phosphate groups of the plant biomass can be concluded.

Plant cell culture as emerging technology for production of active cosmetic ingredients

Plants have always been the main source for active cosmetic ingredients, having proven health beneficial effects on human, such as anti-aging, antioxidant, anti-inflammatory, UV-protective, anti-cancer, anti-wrinkle, skin soothing, whitening, moisturizing, etc. Extracts from herbal, aromatic and/or medicinal plants have been widely used as effective active ingredients in cosmeceuticals or nutricosmetics, especially in products for topical application and skin-care formulations. However, over the past decade, there has been an increasing interest to plant cell culture - derived active cosmetic ingredients. These are "new generation" of high quality natural products, produced by the modern plan biotechnology methods, which usually showed stronger activities than the plant extracts obtained by the classical methods. In this review, the advantages and the current progress in plant cell culture technology for the production of active cosmetic ingredients have been summarized, and discussed in details within a presented case study for calendula stem cell product development.

ROS-dependent signalling pathways in plants and algae exposed to high light: Comparisons with other eukaryotes

Like all aerobic organisms, plants and algae co-opt reactive oxygen species (ROS) as signalling molecules to drive cellular responses to changes in their environment. In this respect, there is considerable commonality between all eukaryotes imposed by the constraints of ROS chemistry, similar metabolism in many subcellular compartments, the requirement for a high degree of signal specificity and the deployment of thiol peroxidases as transducers of oxidising equivalents to regulatory proteins. Nevertheless, plants and algae carry out specialised signalling arising from oxygenic photosynthesis in chloroplasts and photoautotropism, which often induce an imbalance between absorption of light energy and the capacity to use it productively. A key means of responding to this imbalance is through communication of chloroplasts with the nucleus to adjust cellular metabolism. Two ROS, singlet oxygen (¹O₂) and hydrogen peroxide (H₂O₂), initiate distinct signalling pathways when photosynthesis is perturbed. ¹O₂, because of its potent reactivity means that it initiates but does not transduce signalling. In contrast, the lower reactivity of H₂O₂ means that it can also be a mobile messenger in a spatially-defined signalling pathway. How plants translate a H₂O₂ message to bring about changes in gene expression is unknown and therefore, we draw on information from other eukaryotes to propose a working hypothesis. The role of these ROS generated in other subcellular compartments of plant cells in response to HL is critically considered alongside other eukaryotes. Finally, the responses of animal cells to oxidative stress upon high irradiance exposure is considered for new comparisons between plant and animal cells.

Carotenoid and superoxide dismutase are the most effective antioxidants participating in ROS scavenging in phenanthrene accumulated wheat leaf

Polycyclic aromatic hydrocarbons (PAHs) are a kind of pollutants which could stimulate stress reaction in plant cells. In this study, we systematically verify that PAHs could induce an oxidative stress in plants, and describe their damages on wheat leaf subcellular structure and organelle, together with the contributions of antioxidants working against reactive oxygen species. The observation of transmission electron microscope exhibits that cell structures become plasmolyzed and distorted, and organelles disappear under phenanthrene (a model PAH) treatments. Osmiophilic granules arise with increasing phenanthrene concentrations, displaying the evidence for oxidative stress. As more H₂O₂ produce, and the accumulation of H₂O₂ is a fatal reason for cell death under PAH treatments. Through cluster analysis, Pearson correlation coefficient, principal component analysis and redundancy analysis, carotenoid and superoxide dismutase are the two most effective antioxidants to scavenge superoxide radicals among nine major antioxidants (ascorbate, glutathione, polyamines, α-tocopherol, carotenoid, catalases, ascorbate peroxidase, superoxide dismutase and glutathione-S-transferase), glutathione-S-transferase is a potential antioxidant, and Asa-GSH cycle would turn active under higher phenanthrene treatments. Ascorbate peroxidase and α-tocopherol would cause leaf moisture increase. Thus, this work provides better comprehension on the antioxidant performances and their potential application to improving plants' resistance under PAH pollution in the environment.

Platforms for Recombinant Therapeutic Glycoprotein Production

The majority of FDA-approved biology-derived products are recombinant glycoproteins. These proteins have been used for the treatment of several diseases, with numerous products currently approved for clinical use. The choice of the expression system is a key step toward a successful functional protein production, since glycosylation influences yield, pharmacokinetics, biological activity, and immunogenicity. This chapter covers the general aspects of therapeutic recombinant glycoproteins and the platforms that are being employed for their production.

DNA Diffusion Assay Applied to Plant Cells

DNA diffusion assay is a simple, sensitive and reliable technique which allows the assessment of programmed cell death (PCD) or necrosis events based on nuclear morphology. It consists in isolating nuclei from plant material, which are then embedded in agarose and subjected to lysis in alkaline buffers. Under these conditions, and due to the presence of abundant alkali-labile sites in the DNA, small pieces of DNA diffuse in the agarose gel giving a specific halo appearance when stained with fluorescent dyes like DAPI (4',6-diamidino-2-phenylindole). Here, we describe an optimized protocol for DNA diffusion assay applied to different types of plant cells/tissues, indicating all the critical steps required for a successful experimental procedure.

Detection of Endogenous Nuclear Proteins in Plant Cells: Localizing Nuclear Matrix Constituent Proteins (NMCPs), the Plant Analogs of Lamins

At present, two complementary approaches are used for in situ protein visualization in plant nuclei. Imaging of transformed fluorescent proteins is the election tool for the analysis of protein movement and interaction. However, this methodology presents several drawbacks for the identification/localization of endogenous nuclear factors, such as over-expression or mislocalization of transformed proteins. In contrast, immunocytochemistry with specific antibodies represents a powerful tool for the localization of endogenous nuclear proteins at their "native" nuclear sub-compartments. In plant cells, the cell wall hampers antibody accessibility during immunocytochemical analysis thereby reducing the effectivity of the technique, particularly in the case of lowly expressed proteins. To overcome this problem in nuclear protein immunodetection, we developed a method based on the in vitro incubation of isolated nuclei with specific antibodies followed by imaging by confocal fluorescence or electron microscopy. Here we describe the application of this methodology to the localization of Nuclear Matrix Constituent Proteins (NMCP), the plant analogs of lamins, of the monocot Allium cepa, using antibodies raised against highly conserved regions of the proteins.

Metabolism of ibuprofen in higher plants: A model Arabidopsis thaliana cell suspension culture system

The uptake and metabolism of ibuprofen (IBU) by plants at the cellular level was investigated using a suspension culture of A. thaliana. Almost all IBU added to the medium (200 μM) was metabolized or bound to insoluble structures in 5 days. More than 300 metabolites were determined by liquid chromatography-high resolution mass spectrometry (LC-HRMS) analysis, and most of these are first reported for plants here. Although hydroxylated derivatives formed by oxidation on the isobutyl side chain were the main first-step products of IBU degradation, conjugates of these products with sugar, methyl and amino acid groups were the dominant metabolites in the culture. The main portion of total added IBU (81%) was accumulated in the extractable intracellular pool, whereas the cultivation medium fraction contained only 19%. The amount of the insoluble cell-wall-bound IBU was negligible (0.005% of total IBU).

Immobilization of Rubia tinctorum L. Suspension Cultures and Biomass Production

Plants are natural sources of valuable secondary metabolites used as pharmaceuticals, agrochemicals, flavors, fragrances, colors, biopesticides, and food additives. There is an increasing demand to obtain these metabolites through more productive plant tissue applications and cell culture methods due to the importance of secondary metabolites.Immobilization of plant cells is a method used in plant cell cultures to induce secondary metabolite production. In this method, plant cells are fixed in or on a supporting material or matrix such as agar, agarose, calcium alginate, glass, or polyurethane foam. In the present study, three natural lignocellulosic materials, loofah sponge, and the long fibers of sisal and jute, were used to immobilize suspended R. tinctorum cells.

Application of Variable Angle Total Internal Reflection Fluorescence Microscopy to Investigate Protein Dynamics in Intact Plant Cells

Variable angle total internal reflection fluorescence microscopy (VA-TIRFM) is an optical method to observe the molecular events occurring in an extremely thin region near the plasma membrane. Recently, the VA-TIRFM technique has been widely used to study fluorescently labeled target molecules in living animal and plant cells. Here, we describe the optical principle of the VA-TIRFM technique and provide a detailed experimental procedure for the study of living plant cells.

Laser Capture Microdissection: Avoiding Bias in Analysis by Selecting Just What Matters

Laser capture microdissection (LCM) is a powerful technique for harvesting specific cells from a heterogeneous population. As each cell and tissue has its unique genetic, proteomic, and metabolic profile, the use of homogeneous samples is important for a better understanding of complex processes in both animal and plant systems. In case of plants, LCM is very suitable as the highly regular tissue organization and stable cell walls from these organisms enable visual identification of various cell types without staining of tissue sections, which can prevent some downstream analysis. Considering the applicability of LCM to any plant species, here we provide a step-by-step protocol for selecting specific cells or tissues through this technology.

Cautions in Measuring In Vivo Interactions Using FRET and BiFC in Nicotiana benthamiana

Bimolecular fluorescence complementation (BiFC) and Förster Resonance Energy Transfer (FRET) are two widely used techniques to investigate protein-protein interactions and subcellular compartmentalization of proteins in complexes. As of January 2015, there were 805 publications retrieved by PUBMED with the query "bimolecular fluorescence complementation" and 11,327 publications retrieved with the query "fluorescence resonance energy transfer". Only a few of these publications describe studies of plant cells. Given the importance and popularity of these techniques, applying them correctly is crucial but unfortunately many studies lack proper controls and verifications. We describe (1) BiFC and FRET problems that are frequently encountered at different stages of the protocols, (2) how to use appropriate controls, and (3) how to apply plant transformation and imaging procedures. We provide step-by-step protocols for the beginner to obtain high quality, artifact-free BiFC and FRET data.

Mechanism of dynamic reorientation of cortical microtubules due to mechanical stress

Directional growth caused by gravitropism and corresponding bending of plant cells has been explored since 19th century, however, many aspects of mechanisms underlying the perception of gravity at the molecular level are still not well known. Perception of gravity in root and shoot gravitropisms is usually attributed to gravisensitive cells, called statocytes, which exploit sedimentation of macroscopic and heavy organelles, amyloplasts, to sense the direction of gravity. Gravity stimulus is then transduced into distal elongation zone, which is several mm far from statocytes, where it causes stretching. It is suggested that gravity stimulus is conveyed by gradients in auxin flux. We propose a theoretical model that may explain how concentration gradients and/or stretching may indirectly affect the global orientation of cortical microtubules, attached to the cell membrane and induce their dynamic reorientation perpendicular to the gradients. In turn, oriented microtubule arrays direct the growth and orientation of cellulose microfibrils, forming part of the cell external skeleton and determine the shape of the cell. Reorientation of microtubules is also observed in reaction to light in phototropism and mechanical bending, thus suggesting universality of the proposed mechanism.

Nitric oxide from a "green" perspective

The molecule nitric oxide (NO) which is involved in practically all biochemical and physiological plant processes has become a subject for plant research. However, there remain many unanswered questions concerning how, where and when this molecule is enzymatically generated in higher plants. This mini-review aims to provide an overview of NO in plants for those readers unfamiliar with this field of research. The review will therefore discuss the importance of NO in higher plants at the physiological and biochemical levels, its involvement in designated nitro-oxidative stresses in response to adverse abiotic and biotic environmental conditions, NO emission/uptake from plants, beneficial plant-microbial interactions, and its potential application in the biotechnological fields of agriculture and food nutrition.

Formation and maintenance of the Golgi apparatus in plant cells

The Golgi apparatus plays essential roles in intracellular trafficking, protein and lipid modification, and polysaccharide synthesis in eukaryotic cells. It is well known for its unique stacked structure, which is conserved among most eukaryotes. However, the mechanisms of biogenesis and maintenance of the structure, which are deeply related to ER-Golgi and intra-Golgi transport systems, have long been mysterious. Now having extremely powerful microscopic technologies developed for live-cell imaging, the plant Golgi apparatus provides an ideal system to resolve the question. The plant Golgi apparatus has unique features that are not conserved in other kingdoms, which will also give new insights into the Golgi functions in plant life. In this review, we will summarize the features of the plant Golgi apparatus and transport mechanisms around it, with a focus on recent advances in Golgi biogenesis by live imaging of plants cells.

Reactive oxygen species: re-evaluation of generation, monitoring and role in stress-signaling in phototrophic organisms

This review provides an overview about recent developments and current knowledge about monitoring, generation and the functional role of reactive oxygen species (ROS) - H2O2, HO2, HO, OH(-), (1)O2 and O2(-) - in both oxidative degradation and signal transduction in photosynthetic organisms including microscopic techniques for ROS detection and controlled generation. Reaction schemes elucidating formation, decay and signaling of ROS in cyanobacteria as well as from chloroplasts to the nuclear genome in eukaryotes during exposure of oxygen-evolving photosynthetic organisms to oxidative stress are discussed that target the rapidly growing field of regulatory effects of ROS on nuclear gene expression.

Primary antioxidant free radical scavenging and redox signaling pathways in higher plant cells

Antioxidants in plant cells mainly include glutathione, ascorbate, tocopherol, proline, betaine and others, which are also information-rich redox buffers and important redox signaling components that interact with cellular compartments. As an unfortunate consequence of aerobic life for higher plants, reactive oxygen species (ROS) are formed by partial reduction of molecular oxygen. The above enzymatic and non-enzymatic antioxidants in higher plant cells can protect their cells from oxidative damage by scavenging ROS. In addition to crucial roles in defense system and as enzyme cofactors, antioxidants influence higher plant growth and development by modifying processes from miotosis and cell elongation to senescence and death. Most importantly, they provide essential information on cellular redox state, and regulate gene expression associated with biotic and abiotic stress responses to optimize defense and survival. An overview of the literature is presented in terms of primary antioxidant free radical scavenging and redox signaling in plant cells. Special attention is given to ROS and ROS-anioxidant interaction as a metabolic interface for different types of signals derived from metabolisms and from the changing environment. This interaction regulates the appropriate induction of acclimation processes or execution of cell death programs, which are the two essential directions for higher plant cells.

An improved optical technique for monitoring plant cell concentration

 An improved optical method was developed to determine cell weight concentrations using a micro-plate reader. Light absorbance was measured by a vertical light beam, which can minimize the cell settling effect found in traditional optical measurements with a horizontal light beam. The use of well plates not only requires very small sample sizes, but also handles a large number of samples at the same time. Absorbance measurements were linearly related to cell weight over the full range of batch culture growth.