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Past Issue in 2015
Volume: 5, Issue: 23
Cancer Biology
Human Blood Component Vaccinia Virus Neutralization Assay
Many therapeutic viruses, such as oncolytic viruses, vaccines, or gene therapy vectors, may be administered by the intravenous route to maximize their delivery to target tissues. Blood components, such as antibody, complement and blood cells (such as neutrophils, monocytes, T cells, B cells or platelets) may result in viral neutralization and therefore reduce the therapeutic efficacy. This protocol will describe an in vitro assay by which to test the interaction of viruses with blood components. The effect of various factors can be isolated through fractionation. While whole blood can offer the most physiologically relevant snapshot, plasma can investigate the effects of antibody in concert with complement, and heat inactivated plasma will interrogate the effect of antibody alone.
Cell Biology
Single Molecule RNA FISH in the Mammalian Oocyte
RNA fluorescence in situ hybridization is a method to localize and measure gene expression in individual cell or tissue. Using multiple specific fluorescently labeled oligonucleotides greatly increases signal-to-noise ratio and thus enables detection of single RNA molecule. Around forty different DNA oligonucleotides designed to common RNA target and labeled with single fluorophore at 3´ terminus hybridizes with target RNA in fixed cells. We adapt this method to visualize target RNA in the mammalian oocyte. The ability to detect single transcript in the mammalian oocyte was challenging due to its large cell size. This method consists of four simple steps: fixation, permeabilization, hybridization and imaging. The protocol is adapted to this large nonattached cell to visualize maternal RNAs. Combination of various fluorophores allows detection of more RNA targets. This method might be used with organelle markers or expanded with immunofluorescence protocol.
Immunology
Isolation of Lymphocytes from Murine Visceral Adipose Tissue
Several studies have shown that the detrimental influence of abdominal obesity on metabolic processes is mediated by the intra-abdominal fat depot. Visceral adipose tissue has been shown to be an independent risk factor for coronary heart disease, hypertension, impaired glucose tolerance and Diabetes Mellitus Type 2 (DM2). Diet-induced obesity in mice, primarily of the C57BL/6J strain, is a commonly used method to study the development of insulin resistance as a model for DM2. The white or visceral adipose tissue (here referred to as VAT), especially the fat around the gonads, is a commonly used organ of study in this model, as it accumulates large numbers of lymphocytes in response to diet-induced obesity. The protocol below describes the isolation of lymphocytes from the stromal vascular fraction (SVF) from VAT.
Excision of Visceral Adipose Tissue from Live Mice (VATectomy)
The visceral adipose tissue (VAT) has been shown to play an important role in various biological functions. It is a storage depot for nutrients and it is an important endocrine organ producing hormones that control systemic metabolism (McGown et al., 2014). Importantly, following diet-induced obesity, VAT accumulates a large number of activated immune cells, which produce cytokines that drive chronic systemic inflammation and promote insulin resistance (Johnson et al., 2012; Wensveen et al., 2015). VAT therefore plays a key role in metabolic, endocrinological and immunological research. To show the importance of this organ in various research models, one may surgically remove the organ in a procedure called VATectomy. This protocol describes the technical procedures required for an efficient VATectomy of the perigonadal fat pads in mice.
Microbiology
Establishing a Biofilm Co-culture of Pseudomonas and Aspergillus for Metabolite Extraction
Filamentous fungi and bacteria form mixed-species biofilms in nature and diverse clinical contexts (Frey-Klett et al., 2011; Peleg et al., 2010). The interactions between fungi and bacteria, often mediated by secreted metabolites, have important ramifications for the biology of the interacting partners (Frey-Klett et al., 2011). This is particularly true for the bacterium Pseudomonas aeruginosa (P. aeruginosa) and the fungus Aspergillus fumigatus (A. fumigatus) which often reside in the same niche such as lungs of cystic fibrosis (CF) patients. Some studies have reported that co-infection with P. aeruginosa and A. fumigatus could lead to a decrease in lung function relative to their respective single species infection (Amin et al., 2010; Peleg et al., 2010). Metabolite extraction and analysis allow for the characterization of specific microbial metabolites in the polymicrobial biofilm. This protocol describes how to prepare the Pseudomonas-Aspergillus co-culture biofilm on solid medium in preparation for metabolite extraction.
The Application of Quercetin to Study the Effect of Hsp70 Silencing on Plant Virus Infection in Nicotiana benthamiana Plants
Pepino mosaic virus (PepMV) is a mechanically-transmitted pathogen affecting tomato plants worldwide. Like with other plant viruses (Verchot, 2012), the heat shock cognate protein 70 homolog (Hsc70) was identified as an interactor of the PepMV coat protein (CP) (Mathioudakis et al., 2012). Here, we describe a pharmacological approach to silence Hsp70 in plants using quercetin (Mathioudakis et al., 2014), an Hsp70 protein expression flavonoid inhibitor (Hosokawa et al., 1990; Manwell and Heikkila 2007). In the case of Hsp70, this methodology represents a faster and easier approach than silencing of Hsp70 by reverse genetics assays, such as VIGS methodology. Fully expanded leaves of 2 to 3 weeks old Nicotiana benthamiana plants were infiltrated, using a syringe, with either quercetin (dissolved in DMSO) or DMSO (control plants). The plants were mechanically inoculated with PepMV virus inocula. The accumulation of Hsp70 and PepMV were analyzed on local leaves by immunoblot analysis 4 days post inoculation.
Plant Science
Terminal Restriction Fragments (TRF) Method to Analyze Telomere Lengths
Chromosome ends - telomeres - are a focus of intensive research due to their importance for the maintenance of chromosome stability. Their shortening due to incomplete replication functions as a molecular clock counting the number of cell divisions, and ultimately results in cell-cycle arrest and cellular senescence. Determination of telomere lengths is an essential approach in telomere biology for research and diagnostic applications. Terminal Restriction Fragments (TRF) analysis is the oldest approach to analyze telomere lengths and remains the “gold standard” even in current studies. This technique relies on the fact that repeated minisatellite telomeric units do not contain target sites for restriction enzymes. Consequently, telomeres remain in relatively long fragments (TRF), whereas the genomic DNA is digested into short pieces. Fragments of telomeric DNA are then visualized by hybridization with radioactively labeled telomeric probe. As TRF include besides telomeres also a short region of telomere-associated DNA up to the first restriction site, results are slightly shifted towards higher TRFs values. Therefore, the use of frequent cutters or their mixtures is recommended to minimize this difference. Moreover, by using TRF analysis it is possible to distinguish genuine (terminal) telomeres from interstitial telomeric repeats (ITR) (Richards and Ausubel, 1988). In this approach, BAL31 digestion is first applied on high molecular weight DNA. The enzyme progressively degrades linear DNA from its ends. The degraded DNA is then digested with one or more restriction enzymes and fragments are separated by gel electrophoresis. After blotting, membranes are probed with either a terminal marker sequence or telomeric sequence. Genuine TRF can be distinguished from ITR due to their progressive shortening with increasing BAL31 digestion time, while ITR are BAL31-resistant. The TRF BAL31 digestion pattern at the time zero indicates the approximate telomere lengths (Fajkus et al., 2005).
Purification of Rubisco from Chlamydomonas reinhardtii
Chlamydomonas reinhardtii is a model organism for chloroplast studies. Besides other convenient features, the feasibility of chloroplast genome transformation distinguishes this unicellular alga as ideal for the manipulation of chloroplastic gene expression aiming biotechnological goals, such as improved biofuel and biomass production. Ribulose 1, 5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39, Rubisco) is the photosynthetic carbon-fixing enzyme which is considered crucial for biomass accumulation in algal cultures. Purification of wild type and site-directed mutants of Rubisco in C. reinhardtii is usually performed to study its catalytic properties and assess the carbon-fixing potential of the strains. In this protocol Rubisco is extracted through sonication of cell pellets, and purified by ammonium sulfate precipitation, sucrose gradient centrifugation (Goldwaithe and Bogorad, 1975) and anion exchange chromatography.
Quantification of the Volume and Surface Area of Symbiosomes and Vacuoles of Infected Cells in Root Nodules of Medicago truncatula
Legumes are able to form endosymbiotic interactions with nitrogen-fixing rhizobia. Endosymbiosis takes shape in formation of a symbiotic organ, the root nodule. Medicago truncatula (M. truncatula) nodules contain several zones representing subsequent stages of development. The apical part of the nodule consists of the meristem and the infection zone. At this site, bacteria are released into the host cell from infection threads. Upon release, bacteria are surrounded by a host cell-derived membrane to form symbiosomes. After release, rhizobia grow, divide, and gradually colonize the entire host cell of the fixation zone of root nodules. Therefore, mature infected cells contain thousands of symbiosomes, which remain as individual units among other organelles. Visualization of the organization and dynamics of the symbiosomes as well as other organelles in infected cells of nodules is essential to understand mechanisms regulating the development of endosymbiosis between plants and rhizobia. To examine this highly dynamic developmental process, we designed a useful imaging technique that is based on confocal scanning microscopy combined with different fluorescent dyes and GFP-tagged proteins (Gavrin et al., 2014). Here, we describe a protocol for microscopic observation, 3D rendering, and volume/area measurements of symbiosomes and other organelles in infected cells of M. truncatula root nodules. This protocol can be applied for monitoring the development of different host-microbe interactions whether symbiotic or pathogenic.
Analysis of Developing Pollen Grains within Intact Arabidopsis thaliana Anthers by Olympus Two-Photon Laser Scanning Microscopy
The method consists of imaging developing pollen grains as they form within intact, immature Arabidopsis thaliana anthers. Using two-photon excitation in the infrared wavelength range, the intrinsic fluorescence (autofluorescence) of developing pollen grains and surrounding sporophytic tissues of the anther wall, including the tapetum, middle layer, endothecium and epidermis, can be visualized in the three-dimensional space of an intact anther. In contrast to conventional confocal microscopy, the application of red-shifted light by two-photon microscopy improves depth penetration into specimens, while the scattering of light and subsequent phototoxicity is minimized, making this a superior method for imaging the developing pollen grains and tapetal cells enclosed within anthers. The technique described was optimized for the detection of autofluorescent components of the pollen wall, including sporopollenin and the pollen coat, and provided spatial and developmental data on the autofluorescent metabolites in anthers of wild-type and pollen wall mutant plants (Quilichini et al., 2014). The use of two-photon imaging of live, intact anthers holds potential for future studies aimed at understanding the spatial relationship between gametophytic and sporophytic tissues during pollen development and the distribution of metabolites or fluorescently-tagged proteins within developing anthers.
Assay of the Carboxylase Activity of Rubisco from Chlamydomonas reinhardtii
The performance of the carbon-fixing enzyme, ribulose 1, 5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39, Rubisco), controls biomass accumulation in green plants, algae and most autotrophic bacteria. In particular, the carboxylase activity of Rubisco incorporates carbon from CO2 to ribulose 1, 5-bisphosphate (RuBP) producing two molecules of 3-phosphoglycerate. Here a detailed protocol is given for the assay of the carboxylase activity of Rubisco from Chlamydomonas reinhardtii, a model organism for chloroplast studies and a fitting host for biotechnologically oriented genetic manipulation of the enzyme. Rubisco has to be pre-incubated with Mg2+ ions and bicarbonate to induce the catalytically competent active center (Laing and Christeller, 1976). Once Rubisco is activated, the assay of its carboxylase activity described here is based on the fixation of 14C-carbon dioxide/bicarbonate into acid-resistant radioactivity (Lorimer et al., 1977). Although a spectrophotometric assay is also available (Lilley and Walker, 1974), the method based on fixation of a radioactive substrate is irreplaceable when processing a large number of samples, and it is still the technique most often used for the determination of Rubisco activity.
Chlorophyll Content Assay to Quantify the Level of Necrosis Induced by Different R Gene/Elicitor Combinations after Transient Expression
This assay can be used to rapidly and accurately quantify levels of leaf necrosis induced after transient expression of R genes and elicitor combinations (Harris et al., 2013). It is based on the inverse correlation between level of necrosis and chlorophyll content in leaf tissue. It is adapted from the calculations described by (Strain et al., 1971).
Measurement of H+ Flux in Rice by Non-invasive Micro-test Technology
Rice plants release proton (H+) from root cells into rhizosphere area leading to the acidification of the rhizosphere and increased solubility of ferric iron complexes on the cell membrane, which is important for iron uptakes. Here, we present a detailed protocol to measure H+ flux in root hairs of transgenic rice seedlings and transgenic rice protoplasts by the Non-invasive Micro-test Technique (NMT). The NMT system is based on a non-invasive microelectrode technology that is automatically controlled by a computer, to achieve a three-dimensional, real-time, dynamic characterization of the concentration, velocity, and direction of a variety of molecules or ions. Because there is no need to directly contact the measured cells that could cause cell damage, we are able to obtain accurate and real time information on ion concentration. This is the first protocol that describes the non-invasive micro measurement technique of both root hairs and protoplasts in rice. In NMT, voltage differences are measured at two excursion points that are manipulated using a computer. Voltage differences can be converted into H+ fluxes using the ASET 2.0 (The imFlux® software) and JCal v3.2.1 Software. Analysis of the H+ fluxes provides a simultaneous measure of the crossing of a localized region of the root surface in response to stress, which provides real-time in-situ detection of net ion transport across membranes. This method will promote use of NMT in plant biology.
Extraction of Intracellular and Cell Wall Proteins from Leaves and Roots of Harsh Hakea
Plant proteins can be targeted to intracellular (i.e., cytosol, vacuole, organelles etc.) or extracellular (i.e., cell walls, apoplast) compartments. Dual targeting is a key mechanism with important implications for plant metabolism, growth, development and defense etc. Harsh Hakea (Hakea prostrata R.Br.) is a perennial species and member of the Proteaceae family that thrives on extremely phosphate impoverished soils of southwestern Australia. Harsh Hakea is not a common model organism, but has been widely developed for physiological and molecular/biochemical studies of the endogenous adaptations of an ‘extremophile’ plant species to abiotic stress, including low phosphorus tolerance. Tissues of Harsh Hakea contain large amounts of compounds (e.g., phenolics) that interfere with the extraction of soluble proteins. We previously optimised extraction of intracellular proteins from Harsh Hakea proteoid roots to improve soluble protein yield by at least 10-fold (Shane et al., 2013). Here, we describe the protocol for extraction and separation of intracellular from ‘loosely bound’ cell-wall proteins in Harsh Hakea.
Rhizosphere Acidification Assay
Plant survival depends on the ability of root systems to establish themselves in locations where water and nutrients are available for uptake and translocation (Hawes et al., 2003). Rhizosphere influences crop productivity by mediating efficient nutrient transformation, acquisition, and use (Shen et al., 2013). Rhizosphere acidification is a central mechanism for plant mineral nutrition since it contributes to nutrient solubility and the proton motive force (pmf). This pmf is generated by the plasma membrane H+-ATPases (Miller and Smith, 1996; Forde, 2000) in root epidermal and cortical cells, and is coupled to active nutrient acquisition (e.g., N, K, P). Roots are able to acidify the rhizosphere by up to two pH units compared to the surrounding bulk soil mainly through the release of protons, but also bicarbonate, organic acids and CO2. Here we present an easy and inexpensive protocol to quantify protons released to the media by the root system-a method successfully used in our recently published work (Pizzio et al., 2015).