Plant Science

Extracellular vesicles are membrane-bound organelles that play crucial roles in intercellular communication and elicit responses in the recipient cell, such as defense responses against pathogens. In this study, we have optimized a protocol for isolating extracellular vesicles (EVs) from Sorghum bicolor apoplastic wash. We characterized the EVs using fluorescence microscopy and correlative light and electron microscopy.

Fatty acids (FAs) are carboxylic acids with long aliphatic chains that may be straight, branched and saturated or unsaturated. Most of the naturally occurring plant FAs contains an even number of carbon (C4-C24). FAs are used in food and pharmacological industries due to their nutritional importance. In addition, FAs are considered as a promising alternative for the production of biodiesel from terrestrial plant biomass. To establish commercial applications, more reliable analytical methods are needed for the identification, quantification, and composition determination of FAs. Here, we describe a relatively rapid and sensitive method for the extraction, identification, and quantification of FAs from a small quantity of plant tissue. The method includes steps of lipid extraction, conversion of lipid to fatty acid methyl esters (FAMEs) by transmethylation, identification and quantification of FAMEs using gas chromatography-mass spectrometry (GC-MS). In this protocol, an internal standard is added prior to GC-MS analysis. The amount of each FA is calculated from its peak area relative to the peak area of the internal standard.

Lipid peroxidation is a physiological indicator of both biotic and abiotic stress responses, hence is often used as a biomarker to assess stress-induced cell damage or death. Here we demonstrate an easy, quick and cheap staining method to assess lipid peroxidation in plant tissues. In this methodology, Schiff’s reagent, is used to assay for membrane degradation. Histochemical detection of lipid peroxidation is performed in this protocol. In brief, Schiff’s reagent detects aldehydes that originate from lipid peroxides in stressful condition. Schiff’s reagent is prepared and applied to plants tissue. After the reaction, plant tissue samples are rinsed with a sulfite solution to retain the staining color. From this analysis, qualitative visualization of lipid peroxidation in plant tissue is observed in the form of magenta coloration. This reagent is useful for visualization of stress induced lipid peroxidation in plants. In this protocol, Indica rice root, Assam tea root and Indian mustard seedlings are used for demonstration.

Lipid transfer from host plants to arbuscular mycorrhiza fungi was hypothesized for several years because sequenced arbuscular mycorrhiza fungal genomes lack genes encoding cytosolic fatty acid synthase (Wewer et al., 2014; Rich et al., 2017). It was finally shown by two independent experimental approaches (Jiang et al., 2017; Keymer et al., 2017; Luginbuehl et al., 2017). One approach used a technique called isotopolog profiling (Keymer et al., 2017). Isotopologs are molecules, which differ only in their isotopic composition. For isotopolog profiling an organism is fed with a heavy isotope labelled precursor metabolite. Subsequently, the labelled isotopolog composition of metabolic products is analysed via mass spectrometry. The detected isotopolog pattern of the metabolite(s) of interest yields information about metabolic pathways and fluxes (Ahmed et al., 2014). The following protocol describes an experimental setup, which enables separate isotopolog profiling of fatty acids in plant roots colonized by arbuscular mycorrhiza fungi and their associated fungal extraradical mycelium, to elucidate fluxes between both symbiotic organisms. We predict that this strategy can also be used to study metabolite fluxes between other organisms if the two interacting organisms can be physically separated.

Triacylglycerols (TAGs) are esters formed from one glycerol and three fatty acids. TAGs are induced to accumulate in algal cells under environmental stress conditions including nutrient-limitation, hyperosmosis, and low temperature, for the storage of metabolic energy and carbon, and also for the consumption of excess energy (e.g., Hirai et al., 2016; Hayashi et al., 2017). Beside their physiological significance, the commercial utilization of algal TAG has been expected for the production of biodiesel, the methyl esters of fatty acids, from the aspect of carbon-neutral conception. The amounts of TAGs can be determined through quantitative measurement of their constituent fatty acids. This protocol consists of the following three parts: the first is the extraction of total lipids from algal cells with the use of organic solvents, chloroform and methanol, according to the method of Bligh and Dyer (1959), the second is the separation of TAG from the other lipid classes by thin-layer chromatography (TLC), and the third is the production of methyl-esterified derivatives of their constitutive fatty acids and subsequent quantitation of them by capillary gas-liquid chromatography (GLC). This protocol adapted from Sato and Tsuzuki (2011) is used for TAG analysis in a green alga, Chlorella kessleri.

Here we describe both non-extraction and solvent-extraction methods for root aliphatic suberin analysis. The non-extraction method is fast as roots are directly depolymerized using acidic transmethylation. However, suberin aliphatic components are isolated together with all the other acyl chains making up the lipids (e.g., membranes) present in roots. For the solvent-extraction method, roots are first delipidated before transmethylation. This method is longer but allows separation of soluble and polymerized root lipids. This protocol is optimized for tissue culture- or soil-grown Arabidopsis thaliana plants, but can be used with roots of other plants.

Fusarium graminearum has been given special attention in the context of agricultural commodities due to its ability to grow in diverse climatic conditions, and to produce different mycotoxins including zearalenone (ZEA) and type-B trichothecenes, which cause ill health effects on humans, animals and plants. The application of synthetic antifungal agents for the control of F. graminearum result in negative health impacts in livestock and humans and the upsurge of resistant organisms as well. Therefore, there is a need to propose proper food grain management practices, including the application of herbal antifungal and mycotoxin controlling agents, to reduce the growth of toxigenic F. graminearum as well as the production of ZEA in agricultural commodities. Ocimum sanctum also known as Holy Basil or Tulsi is widely used as a medicinal plant in Ayurveda. The current protocol demonstrates to quantify the antifungal activity of O. sanctum L. essential oil (OSEO) as reflected by the decreased F. graminearum growth and ZEA production. Antifungal activities of OSEO are carried out by micro well dilution method and further validated quantitatively by scanning electron microscopic methods. Effects of OSEO on ZEA production is analysed by Quantitative reverse transcription PCR (RT-qPCR) and Ultra high performance liquid chromatography (UHPLC) methods from a broth culture of F. graminearum. Anti-mycotoxic efficacy of OSEO is assessed directly on F. graminearum inoculated maize grains. The protocol efficiently assessed the activity of OSEO as an herbal antagonistic agent against fungal infestation and ZEA production by F. graminearum. The protocol can be used to test a wide variety of herbal compounds for antifungal activity against F. graminearum or with modifications on other mycotoxigenic fungi, an important intervention in food safety and processing industries where the fungal infestation is a major concern.

This protocol describes a method to extract total polar glycerol lipids from plant materials, followed by mass spectrometry profiling. Different glycerol lipid classes can be distinguished by their head-groups, which can be profiled automatically and quantitatively by a triple quadrupole mass spectrometry in multiple reaction monitoring (MRM) mode with an autosampler. Comparing with other established methods, such as thin layer chromatography (TLC) separation followed by Gas spectrometry (GC) analysis, this method requires little effort in sample preparation and separation, while the resolution is not limited to general lipid classes but at side chain level. This method was described and used successfully to profile plant lipids changes under freezing stress in Welti et al. (2002).

Plant phospholipids can be produced in the endoplasmic reticulum or plastids. Lipids from different sources can be distinguished by the fatty acid profile, in terms of the preferred fatty acid species esterified to the sn-1 or sn-2 position of the glycerol backbone (Ohlrogge and Browse, 1995). This protocol is used to determine the fatty acid profile in total plant phospholipids by the treatment of sn-2 specific phospholipase A₂ (PLA₂).

Lipid-Protein interaction assay is a method to search lipids, which are bound with proteins in vitro. Since membranes that are spotted with chloroplast lipids such as monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), and sulfoquinovosyldiacylglycerol (SQDG) are not commercially available, we extracted these lipids from cyanobacterial cells and spotted them onto membranes. The prepared membranes could be used for lipid-protein interaction assay.