Name: plant-microbe interaction: transcriptional response of bacillus mycoides to potato root exudates
Uploaded: 2018-07-02T13:00:00
Description: Watch this Scientific Journal Video about Plant-Microbe Interaction: Transcriptional Response of Bacillus Mycoides to Potato Root Exudates at JoVE.com

We thank Jakob Viel for his helpful comments and suggestions. We also thank Anne de Jong for his help in the bioinformatics analysis. Yanglei Yi and Zhibo Li are supported by the China Scholarship Council (CSC). We thank NWO-TTW Perspectief Programma Back2Roots (TKI-AF-15510) for their financial support to OPK.

1. Germinating Potato in Sterilized Conditions
<ol>
	<li>Rinse the potato surface with sterile water. Bathe the potato in 70% ethanol and then in 3% sodium hypochlorite, for 5 min each. Rinse it again with sterile water to remove any remaining sodium hypochlorite.</li>
	<li>Prepare the materials needed for germinating and growing potato tubers; sterilize the plastic pots, engraftment baskets, vermiculite, and water by autoclaving them at 121 &#176;C for 20 min. 
	NOTE: Ensure that all materials used are autoclavab...

<ol>
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M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+and+function+of+root+exudates.">Regulation and function of root exudates.</a> Plant, Cell &amp; Environment. 32 (6), 666-681 (2009).</li><li>Rohrbacher, F., St-Arnaud, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Root+exudation:+the+ecological+driver+of+hydrocarbon+rhizoremediation.">Root exudation: the ecological driver of hydrocarbon rhizoremediation.</a> Agronomy Journal. 6 (1), 19 (2016).</li><li>Mark, G. 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J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterisation+of+systemic+resistance+in+sugar+beet+elicited+by+a+non-pathogenic,+phyllosphere-colonizing+Bacillus+mycoides,+biological+control+agent.">Characterisation of systemic resistance in sugar beet elicited by a non-pathogenic, phyllosphere-colonizing Bacillus mycoides, biological control agent.</a> Physiological and Molecular Plant Pathology. 61 (5), 289-298 (2002).</li><li>Peng, Y. -. 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Plant-microbe interactions have been hypothesized to be determined by a finely tuned equilibrium between bacteria and plants. Such interactions are highly complex and difficult to study in a natural system, which comprises diverse microbial species, potentially acting as consortia. This paper describes a simplified protocol to study the bacterial response to root exudates under well-controlled conditions. The transcriptome profile of rhizobacteria, upon exposure to root exudates, provides detailed information on bacteria...

Plants may exudate up to 20% of the carbon fixed during photosynthesis through roots into the rhizosphere1, i.e., the narrow zone of soil near the roots. Due to the higher nutrient availability, the rhizosphere is a suitable habitat for diverse microorganisms, including plant-growth promoting bacteria. The root exudates contain a range of inorganic compounds like ions, inorganic acids, oxygen, and water. However, the majority of the root exudates is formed by organic materials, which can be divided into low molecular weight compounds and high molecular weight compounds. The low molecular weight compounds include amino acids, organic acids, sugars, phenolic compounds, fatty acids, and an array of secondary metabolites. The high molecular weight compounds consist of mucilage and proteins2,3. Rhizosphere microorganisms can use some of these compounds as an energy source for growth and development. The root exudates play an important role in shaping the rhizobacterial community since the plant-produced compounds in the exudates can influence the behavior of rhizosphere-associated bacteria by affecting the expression of specific genes.
Understanding the bacterial response to root exudates is a key step in deciphering plant-microbe interaction mechanisms. As the bacterial response to plant-microbe interactions is the product of differential gene expression, it can be studied by transcriptome analysis. Using this method, previous studies identified several important genes involved in plant-microbe interactions. In Pseudomonas aeruginosa, genes involved in metabolism, chemotaxis, and type II secretion were shown to respond to sugar beet root exudates4. Fan et al.5 studied the transcriptomic profiling of B. amyloliquefaciens FZB42 in response to maize root exudates. Their results show that, of the genes strongly induced by the root exudates, several groups are involved in metabolic pathways relating to nutrient utilization, chemotaxis, motility, and non-ribosomal synthesis of antimicrobial peptides and polyketides.
The accuracy of these studies relies on the collection of root exudates. Although several methods have described the collection of root exudates for different purposes, they either demand sophisticated instruments or are not performed in well-controlled conditions6,7,8. Moreover, rhizosphere-inhibiting microorganisms can influence root exudate composition by affecting plant cell membrane permeability and damaging the root tissues, particularly in the case of consortia of microorganisms9. When investigating the microbial response to root exudates, it is important to use well-defined conditions in order to avoid alteration of the compounds by other microorganisms10. Furthermore, high-quality RNA is required for RNA-seq based transcriptome studies. However, when dealing with non-model-bacterial strains, the standard protocols or commercial kits usually have a low efficiency due to unknown factors or special growth properties.
The protocol described here was verified using B. mycoides, which is a gram-positive, spore-forming bacterium of the Firmicute phylum. It is ubiquitous in the rhizosphere of various plant species. Several plant growth promoting properties have been reported for this species, including induction of systematic resistance (ISR) in sugar beet11, inhibition of the damping-off pathogen Pythium for cucumber12, as well as nitrogen fixation in the sunflower rhizosphere13. However, the molecular mechanisms of its interaction with a host plant are not well studied.
The objective of the experiments presented here is to study the transcriptomic response of endosphere-isolated B. mycoides to potato root exudates. In short, the protocol consists of the following steps: first, collect potato root exudates under sterile conditions. Then, extract high-quality RNA from bacterial cells treated with root exudates. The final step is data analysis using the web-based T-REx pipeline14. This protocol was used to identify B. mycoides genes that show a shift in expression levels upon contact with root-exudates and thus might play an important role in plant-microbe interactions.

<table border="0" cellpadding="0" cellspacing="0" width="987">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:260px;">sodium hypochlorite</td>
			<td style="width:236px;">Sigma</td>
			<td style="width:152px;">&#160;CAS: 7681-52-9&#160;</td>
			<td style="width:339px;">10-15%&#160; active chlorine</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:260px;">Luria-Bertani (LB) broth</td>
			<td style="width:236px;"></td>
			<td style="width:152px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:260px;">incubater</td>
			<td style="width:236px;">New Brunswick Scientific</td>
			<td style="width:152px;">Innova 4000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">spectrophotometer</td>
			<td style="width:236px;">Thermo Fisher Scientific</td>
			<td style="width:152px;">Genesys 20</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:260px;">liquid nitrogen</td>
			<td style="width:236px;"></td>
			<td style="width:152px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:260px;">glass beads</td>
			<td style="width:236px;">Sigma</td>
			<td style="width:152px;">G8893</td>
			<td>0.5 &#181;m</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:260px;">2.0 ml tube with screw cap</td>
			<td style="width:236px;"></td>
			<td style="width:152px;"></td>
			<td>RNase free</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:260px;">1.5 ml and 2.0 ml eppendorf tube</td>
			<td style="width:236px;"></td>
			<td style="width:152px;"></td>
			<td>RNase free</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Bead mill homogenizer</td>
			<td>BioSpec</td>
			<td style="width:152px;">607</td>
			<td>Mini_beadbeater</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:260px;">centrifuge</td>
			<td style="width:236px;">Eppendorf</td>
			<td style="width:152px;">5430</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:260px;">Diethyl pyrocarbonate (DEPC)</td>
			<td style="width:236px;">sigma</td>
			<td style="width:152px;">CAS: 1609-47-8</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:260px;">Sodium Dodecyl Sulfate (SDS)</td>
			<td style="width:236px;">sigma</td>
			<td style="width:152px;">CAS: 151-21-3&#160;</td>
			<td>10% solution prepared with DEPC treated MQ water</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:260px;">TE buffer</td>
			<td style="width:236px;"></td>
			<td style="width:152px;"></td>
			<td>10 mM Tris-HCl; 1 mM EDTA, pH=8</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:260px;">phenol</td>
			<td>Sigma</td>
			<td style="width:152px;"></td>
			<td>RNA grade</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:260px;">chloroform-isoamyl alcohol&#160;</td>
			<td style="width:236px;"></td>
			<td style="width:152px;"></td>
			<td>prepare 24:1 of chloroform:isoamyl alcohol, store at room temperature</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:260px;">High pure RNA isolation kit</td>
			<td style="width:236px;">Roche</td>
			<td style="width:152px;">11828665001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:260px;">RNase Decontamination Solution</td>
			<td style="width:236px;">Invitrogen</td>
			<td style="width:152px;">AM9780</td>
			<td>RNase-Zap</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:260px;">Automated electrophoresis instrument</td>
			<td style="width:236px;">Agilent</td>
			<td style="width:152px;">2100</td>
			<td>Bioanalyzer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Microvolume spectrophotometer</td>
			<td style="width:236px;">Thermo Fisher Scientific</td>
			<td style="width:152px;">Nanodrop ND-1000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:260px;">RNA quality analysis kit</td>
			<td style="width:236px;">Agilent</td>
			<td style="width:152px;">RNA 6000 Nano kit&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:260px;">RNase inhibitor</td>
			<td style="width:236px;">Thermo Fisher Scientific</td>
			<td style="width:152px;">RiboLock</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:260px;">Directional RNA library Prep kit</td>
			<td style="width:236px;">NEB</td>
			<td style="width:152px;">Ultra</td>
			<td style="width:339px;">For Illumina</td>
		</tr>
	</tbody>
</table>

plant-microbe interaction: transcriptional response of bacillus mycoides to potato root exudates

Beneficial plant-associated bacteria play an important role in promoting growth and preventing disease in plants. The application of plant growth-promoting rhizobacteria (PGPR) as biofertilizers or biocontrol agents has become an effective alternative to the use of conventional fertilizers and can increase crop productivity at low cost. Plant-microbe interactions depend upon host plant-secreted signals and a reaction hereon by their associated bacteria. However, the molecular mechanisms of how beneficial bacteria respond to their associated plant-derived signals are not fully understood. Assessing the transcriptomic response of bacteria to root exudates is a powerful approach to determine the bacterial gene expression and regulation under rhizospheric conditions. Such knowledge is necessary to understand the underlying mechanisms involved in plant-microbe interactions. This paper describes a detailed protocol to study the transcriptomic response of B. mycoides EC18, a strain isolated from the potato endosphere, to potato root exudates. With the help of recent high-throughput sequencing technology, this protocol can be performed in several weeks and produce massive datasets. First, we collect the root exudates under sterile conditions, after which they are added to B. mycoides cultures. The RNA from these cultures is isolated using a phenol/chloroform method combined with a commercial kit and subjected to quality control by an automated electrophoresis instrument. After sequencing, data analysis is performed with the web-based T-REx pipeline and a group of differentially expressed genes is identified. This method is a useful tool to facilitate new discoveries on the bacterial genes involved in plant-microbe interactions.

Plant-associated microorganisms can positively influence plant growth and health. However, the mechanisms of the complex interactions between plants and their microbial symbionts are not fully understood. Root exudates play an important role in regulating the rhizobacterial activity and behavior, and it is generally postulated that the microbial colonization of roots initiates with the attraction of microbes to root exudates. The aim of this work was to investigate the transcriptomic resp...

Watch this Scientific Journal Video about Plant-Microbe Interaction: Transcriptional Response of Bacillus Mycoides to Potato Root Exudates at JoVE.com

Plant-Microbe Interaction: Transcriptional Response of Bacillus Mycoides to Potato Root Exudates

The goal of the protocol presented here is to study the transcriptomic response of endosphere-isolated Bacillus mycoides to potato root exudates. This method facilitates the identification of important bacterial genes involved in plant-microbe interactions and is in principle applicable to other endophytes and plants, with minor adjustments.

Plant-Microbe Interaction: Transcriptional Response of Bacillus Mycoides to Potato Root Exudates

Beneficial plant-associated bacteria play an important role in promoting growth and preventing disease in plants. The application of plant ...

This method can help to answer key questions in the fields of plant-microbe interaction. You can, for instance, identify important genes from bacterial strains that were isolated from the endosphere or rhizosphere during the interaction of the bacteria with the plant. It's a versatile method that can also be used for studies on other bacteria with plants.The main advantage of this technique is that in a relatively short period a large number of bacteria genes that are important during plant-microbe interactions can be identified. To begin this procedure, rinse the potato surface with sterile water. Bathe the potato in 70%ethanol for five minutes and then in 3%sodium hypochlorite for another five minutes.Afterward, rinse it again with sterile water to remove any remaining sodium hypochlorite. Next, prepare the materials needed for germinating and growing potato tubers. Sterilize the plastic pots, engraftment baskets, vermiculite, and water by autoclaving them at 121 degrees Celsius for 20 minutes.Subsequently, put the surface-sterilized potato into the engraftment basket and place it in an autoclaved pot containing wet vermiculite. Use a large glass fiber box to cover the pot to avoid microbial contaminations. Keep the pot in a climate chamber at 24 degrees Celsius for three weeks, and set it on cycles of 16 hours of light and 8 hours of darkness.To collect the potato root exudates, when the shoots sprout, transfer the basket with the whole potato into a sterilized beaker filled with 150 milliliters of autoclaved deionized water with the potato tubers placed just above the water surface and the roots submerged in the water. Keep the seedling in the climate chamber, and use the same settings as before. From the second day on, collect the water containing the exudates, and refill the beaker with sterile, deionized water.Then store each sample separately at four degrees Celsius. For each sample, spread 100 microliters on a Luria-Bertani agar plate to check for microbial contaminations. Discard the contaminated samples.Combine the collected samples of one seedling. Then transfer the combined root exudates into 50 milliliter tubes. Freeze the tubes containing root exudates at minus 80 degrees Celsius.Concentrate them by freeze drying them at minus 40 degrees Celsius to a final volume of 150 milliliters. To grow the bacteria, streak a B.mycoides strain from a minus 80 degree Celsius glycerol stock onto an LB agar plate, and incubate the plate at 30 degrees Celsius overnight. Then inoculate the LB liquid medium with a single colony from the plate, and grow the culture in a shaking incubator at 200 rpm overnight at 30 degrees Celsius.To treat and sample the bacteria, dilute an overnight B.mycoides culture with 90 milliliters of pre-warmed LB medium to the initial OD600 of zero point zero five in a 300 milliliter flask. Subsequently, add 10 milliliters of root exudates to the culture, and use a 10 milliliter sterile, deionized water treatment as a control. Then incubate them at 30 degrees Celsius for one hour.After an hour, transfer the culture into 50 milliliter centrifuge tubes. Collect the cells from the culture by centrifugation at 9, 000 times G for two minutes at four degrees Celsius. Afterward, discard the supernatent, and immediately freeze the pellet in liquid nitrogen.Then store it at minus 80 degrees Celsius until use. To isolate RNA, thaw the cell pellets on ice, and suspend each of them in 400 microliters of TE buffer. Then transfer the suspensions into the two milliliter screw cap tubes.Add zero point five grams of glass beads into the tube. Then close the caps firmly and place the tubes in a bead mill homogenizer. Perform a 45-second pulse homogenization three times, with a one-minute interval on ice.Afterward, centrifuge the samples for 10 minutes at 11, 000 times G, and transfer the upper phase of each sample to a new tube. Add 500 microliters of chloroform:isoamyl alcohol to the upper phase, and centrifuge the mixture for five minutes at 11, 000 times G.Then transfer 500 microliters of the upper phase to a fresh tube. Add one milliliter of the lysis binding buffer, and mix it by pipetting up and down.Next, prepare one point five milliliter microcentrifuge tubes with 100 microliters of DNase buffer, 10 microliters of DNase I, and five microliters of an RNase inhibitor. Add the prepared solution mix on the filter of the filter tubes, and incubate them for 20 to 30 minutes at 15 to 25 degrees Celsius. Subsequently, perform the washing steps according to the manufacturer's instruction, and add 50 microliters of an elusion buffer to the tube.After centrifugation, elute the RNA. Transfer a few microliters of the sample to a one point five milliliter microcentrifuge tube to perform a quality check. Finally, cover the eluded RNA with a plastic paraffin film and keep it at minus 80 degrees Celsius.After collection, the root exudates were added to the B.mycoides culture at a 10%ratio, and the bacterial total RNA was isolated. The RNA was then subjected to a quality check by an automated electrophoresis instrument. These graphs represent the RNA isolated from B.mycoides treated with the root exudates, and these graphs represent the RNA isolated from the control group.All samples scored a RIN value above nine, with two clear bands corresponding to the 16S and 23S RNA subunits, demonstrating that high-quality RNA was obtained by this protocol. After library preparation, pair end reads were obtained with a high-throughput sequencing platform. The raw RNA-seq reads were trimmed from the adaptor sequences, and mapped against the reference genome sequence.The transcript home analysis was performed with the T-REx pipeline, and the ratio intensity plot of all the differentially expressed genes is shown here. After the potentially important gene's been identified, other in vivo methods like promoter GFP fusion, cue-pews-air, and fluorescent in situ hybridization can be performed in order to answer additional questions like time in reserved expression of certain genes during the interaction with host plant.

plant-microbe-interaction-transcriptional-response-bacillus-mycoides

Research

JoVE Journal

Biology

Virus-induced Gene Silencing (VIGS) in Nicotiana benthamiana and Tomato

RNA interference (RNAi) is a highly specific gene-silencing phenomenon triggered by dsRNA1. This silencing mechanism uses two major classes of RNA regulators: microRNAs, which are produced from non-protein coding genes and short interfering RNAs (siRNAs). Plants use RNAi to control transposons and to exert tight control over developmental processes such as flower organ formation and leaf development2,3,4. Plants also use RNAi to defend themselves against infection by viruses. Consequently, many viruses have evolved suppressors of gene silencing to allow their successful colonization of their host5.
Virus-induced gene silencing (VIGS) is a method that takes advantage of the plant RNAi-mediated antiviral defense mechanism. In plants infected with unmodified viruses the mechanism is specifically targeted against the viral genome. However, with virus vectors carrying sequences derived from host genes, the process can be additionally targeted against the corresponding host mRNAs. VIGS has been adapted for high-throughput functional genomics in plants by using the plant pathogen Agrobacterium tumefaciens to deliver, via its Ti plasmid, a recombinant virus carrying the entire or part of the gene sequence targeted for silencing. Systemic virus spread and the endogenous plant RNAi machinery take care of the rest. dsRNAs corresponding to the target gene are produced and then cleaved by the ribonuclease Dicer into siRNAs of 21 to 24 nucleotides in length. These siRNAs ultimately guide the RNA-induced silencing complex (RISC) to degrade the target transcript2.
Different vectors have been employed in VIGS and one of the most frequently used is based on tobacco rattle virus (TRV). TRV is a bipartite virus and, as such, two different A. tumefaciens strains are used for VIGS. One carries pTRV1, which encodes the replication and movement viral functions while the other, pTRV2, harbors the coat protein and the sequence used for VIGS6,7. Inoculation of Nicotiana benthamiana and tomato seedlings with a mixture of both strains results in gene silencing. Silencing of the endogenous phytoene desaturase (PDS) gene, which causes photobleaching, is used as a control for VIGS efficiency. It should be noted, however, that silencing in tomato is usually less efficient than in N. benthamiana. RNA transcript abundance of the gene of interest should always be measured to ensure that the target gene has efficiently been down-regulated. Nevertheless, heterologous gene sequences from N. benthamiana can be used to silence their respective orthologs in tomato and vice versa8.

Virus-induced Gene Silencing VIGS in Nicotiana benthamiana and Tomato

Description of a virus-induced gene silencing (VIGS) method for knock-down of gene expression in Nicotiana benthamiana and tomato.

RNA interference (RNAi) is a highly specific gene-silencing phenomenon triggered by dsRNA1. This silencing mechanism uses two major classes of RNA ...

Single Cell Transcriptional Profiling of Adult Mouse Cardiomyocytes

While numerous studies have examined gene expression changes from homogenates of heart tissue, this prevents studying the inherent stochastic variation between cells within a tissue. Isolation of pure cardiomyocyte populations through a collagenase perfusion of mouse hearts facilitates the generation of single cell microarrays for whole transcriptome gene expression, or qPCR of specific targets using nanofluidic arrays. We describe here a procedure to examine single cell gene expression profiles of cardiomyocytes isolated from the heart. This paradigm allows for the evaluation of metrics of interest which are not reliant on the mean (for example variance between cells within a tissue) which is not possible when using conventional whole tissue workflows for the evaluation of gene expression (Figure 1). We have achieved robust amplification of the single cell transcriptome yielding micrograms of double stranded cDNA that facilitates the use of microarrays on individual cells. In the procedure we describe the use of NimbleGen arrays which were selected for their ease of use and ability to customize their design. Alternatively, a reverse transcriptase - specific target amplification (RT-STA) reaction, allows for qPCR of hundreds of targets by nanofluidic PCR. Using either of these approaches, it is possible to examine the variability of expression between cells, as well as examining expression profiles of rare cell types from within a tissue. Overall, the single cell gene expression approach allows for the generation of data that can potentially identify idiosyncratic expression profiles that are typically averaged out when examining expression of millions of cells from typical homogenates generated from whole tissues.

Single cell expression profiling allows the detailed gene expression analysis of individual cells. We describe methods for the isolation of cardiomyocytes, and preparing the resulting lysates for either whole transcriptome microarray or qPCR of specific targets.

While numerous studies have examined gene expression changes from homogenates of heart tissue, this prevents studying the inherent stochastic variation ...

Using Flatbed Scanners to Collect High-resolution Time-lapsed Images of the Arabidopsis Root Gravitropic Response

Research efforts in biology increasingly require use of methodologies that enable high-volume collection of high-resolution data. A challenge laboratories can face is the development and attainment of these methods. Observation of phenotypes in a process of interest is a typical objective of research labs studying gene function and this is often achieved through image capture. A particular process that is amenable to observation using imaging approaches is the corrective growth of a seedling root that has been displaced from alignment with the gravity vector. Imaging platforms used to measure the root gravitropic response can be expensive, relatively low in throughput, and/or labor intensive. These issues have been addressed by developing a high-throughput image capture method using inexpensive, yet high-resolution, flatbed scanners. Using this method, images can be captured every few minutes at 4,800 dpi. The current setup enables collection of 216 individual responses per day. The image data collected is of ample quality for image analysis applications.

This protocol describes a process for rapid collection of images of Arabidopsis seedlings responding to a gravity stimulus using commercially-available flatbed scanners. The method allows for inexpensive, high-volume capture of high-resolution images amenable for downstream analysis algorithms.

Research efforts in biology increasingly require use of methodologies that enable high-volume collection of high-resolution data. A challenge laboratories ...

Collection and Analysis of Arabidopsis Phloem Exudates Using the EDTA-facilitated Method

The plant phloem is essential for the long-distance transport of (photo-) assimilates as well as of signals conveying biotic or abiotic stress. It contains sugars, amino acids, proteins, RNA, lipids and other metabolites. While there is a large interest in understanding the composition and function of the phloem, the role of many of these molecules and thus, their importance in plant development and stress response has yet to be determined. One barrier to phloem analysis lies in the fact that the phloem seals itself upon wounding. As a result, the number of plants from which phloem sap can be obtained is limited. One method that allows collection of phloem exudates from several plant species without added equipment is the EDTA-facilitated phloem exudate collection described here. While it is easy to use, it does lead to the wounding of cells and care has to be taken to remove contents of damaged cells. In addition, several controls to prove purity of the exudate are necessary. Because it is an exudation rather than a direct collection of the phloem sap (not possible in many species) only relative quantification of its contents can occur. The advantage of this method over others is that it can be used in many herbaceous or woody plant species (Perilla, Arabidopsis, poplar, etc.) and requires minimal equipment and training. It leads to reasonably large amounts of exudates that can be used for subsequent analysis of proteins, sugars, lipids, RNA, viruses and metabolites. It is simple enough that it can be used in both a research as well as in a teaching laboratory.

Collection and Analysis of Arabidopsis Phloem Exudates Using the EDTA-facilitated Method

Knowledge of the composition of the phloem sap as well as the mechanism of its loading and long-distance transport is essential for the understanding of long-distance signaling in plant development and stress/pathogen response and of assimilate transport. This manuscript describes the collection of phloem exudates using the EDTA-facilitated method.

The plant phloem is essential for the long-distance transport of (photo-) assimilates as well as of signals conveying biotic or abiotic stress. It ...

Methods to Discover Alternative Promoter Usage and Transcriptional Regulation of Murine Bcrp1

Gene expression in different tissues is often controlled by alternative promoters that result in the synthesis of mRNA with unique &#8212; usually untranslated &#8212; first exons. Bcrp1 (Abcg2), the murine orthologue of the ABC transporter Breast Cancer Resistance Protein (BCRP, ABCG2), has at least four alternative promoters that are designated by the corresponding four alternative first exons produced: E1U, E1A, E1B, and E1C. Herein, in-silico protocols are presented to predict alternative promoter usage for Bcrp1. Furthermore, reporter assay methods are described to produce reporter constructs for alternative promoters and to determine the functionality of putative promoters upstream of the alternative first exons that are identified.

With the murine ABC transporter Bcrp1 (Abcg2) as an example, in-silico protocols are presented to detect alternative promoter usage in genes expressed in mouse tissues, and to evaluate the functionality of the alternative promoters identified using reporter assays.

Gene expression in different tissues is often controlled by alternative promoters that result in the synthesis of mRNA with unique &#8212; usually ...

High-throughput CRISPR Vector Construction and Characterization of DNA Modifications by Generation of Tomato Hairy Roots

Targeted DNA mutations generated by vectors with clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 technology have proven useful for functional genomics studies. While most cloning strategies are simple to perform, they generally use multiple steps and can require several days to generate the ultimate constructs. The method presented here is based on DNA assembly and can produce fully functional CRISPR vectors in a single cloning reaction. Vector construction can also be pooled, further increasing the efficiency and utility of the process. A modification of the method is used to create CRISPR vectors with multiple gene targets. CRISPR vectors are then transformed into tomato hairy roots to generate transgenic materials with targeted DNA modifications. Hairy roots are a useful system for testing vector functionality as they are technically simple to generate and amenable to large-scale production. The methods presented here will have wide application as they can be used to generate a variety of CRISPR vectors and be used in a wide range of plant species.

Using DNA assembly, multiple CRISPR vectors can be constructed in parallel in a single cloning reaction, making the construction of large numbers of CRISPR vectors a simple task. Tomato hairy roots are an excellent model system to validate CRISPR vectors and generate mutant materials.

Targeted DNA mutations generated by vectors with clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 technology have proven useful for ...

A Hydroponic Co-cultivation System for Simultaneous and Systematic Analysis of Plant/Microbe Molecular Interactions and Signaling

An experimental design mimicking natural plant-microbe interactions is very important to delineate the complex plant-microbe signaling processes. Arabidopsis thaliana-Agrobacterium tumefaciens provides an excellent model system to study bacterial pathogenesis and plant interactions. Previous studies of plant-Agrobacterium interactions have largely relied on plant cell suspension cultures, the artificial wounding of plants, or the artificial induction of microbial virulence factors or plant defenses by synthetic chemicals. However, these methods are distinct from the natural signaling in planta, where plants and microbes recognize and respond in spatial and temporal manners. This work presents a hydroponic cocultivation system where intact plants are supported by metal mesh screens and cocultivated with Agrobacterium. In this cocultivation system, no synthetic phytohormone or chemical that induces microbial virulence or plant defense is supplemented. The hydroponic cocultivation system closely resembles natural plant-microbe interactions and signaling homeostasis in planta. Plant roots can be separated from the medium containing Agrobacterium, and the signaling and responses of both the plant hosts and the interacting microbes can be investigated simultaneously and systematically. At any given timepoint/interval, plant tissues or bacteria can be harvested separately for various &#34;omics&#34; analyses, demonstrating the power and efficacy of this system. The hydroponic cocultivation system can be easily adapted to study: 1) the reciprocal signaling of diverse plant-microbe systems, 2) signaling between a plant host and multiple microbial species (i.e.&#160;microbial consortia or microbiomes), 3) how nutrients and chemicals are implicated in plant-microbe signaling, and 4) how microbes interact with plant hosts and contribute to plant tolerance to biotic or abiotic stresses.

The described hydroponic cocultivation system supports intact plants with metal mesh screens and cocultivates them with bacteria. Plant tissue, bacteria, and secreted molecules can then be separately harvested for downstream analyses, simultaneously allowing for the molecular responses of both plant hosts and interacting microbes or microbiomes to be investigated.

An experimental design mimicking natural plant-microbe interactions is very important to delineate the complex plant-microbe signaling processes. ...

Single-cell Microfluidic Analysis of Bacillus subtilis

Microfluidic technology overcomes many of the limitations to traditional analytical methods in microbiology. Unlike bulk-culture methods, it offers single-cell resolution and long observation times spanning hundreds of generations; unlike agarose pad-based microscopy, it has uniform growth conditions that can be tightly controlled. Because the continuous flow of growth medium isolates the cells in a microfluidic device from unpredictable variations in the local chemical environment caused by cell growth and metabolism, authentic changes in gene expression and cell growth in response to specific stimuli can be more confidently observed. Bacillus subtilis is used here as a model bacterial species to demonstrate a &#34;mother machine&#34;-type method for cellular analysis. We show how to construct and plumb a microfluidic device, load it with cells, initiate microscopic imaging, and expose cells to a stimulus by switching from one growth medium to another. A stress-responsive reporter is used as an example to reveal the type of data that may be obtained by this method. We also briefly discuss further applications of this method for other types of experiments, such as analysis of bacterial sporulation.

Single-cell Microfluidic Analysis of Bacillus subtilis

We present a method for the microfluidic analysis of individual bacterial cell lineages using Bacillus subtilis as an example. The method overcomes shortcomings of traditional analytical methods in microbiology by allowing observation of hundreds of cell generations under tightly controllable and uniform growth conditions.

Microfluidic technology overcomes many of the limitations to traditional analytical methods in microbiology. Unlike bulk-culture methods, it offers ...

An Improved Chemotaxis Assay for the Rapid Identification of Rhizobacterial Chemoattractants in Root Exudates

Chemotaxis identification is very important for the research and application of rhizosphere growth-promoting bacteria. We established a straightforward method to quickly identify the chemoattractants that could induce the chemotactic movement of rhizosphere growth-promoting bacteria on sterile glass slides via simple steps. Bacteria solution (OD600 = 0.5) and sterile chemoattractant aqueous solution were added dropwise on the glass slide at an interval of 1 cm. An inoculating loop was used to connect the chemoattractant aqueous solution to the bacterial solution. The slide was kept at room temperature for 20 min on the clean bench. Finally, the chemoattractant aqueous solution was collected for bacterial counting and microscopic observation. In this study, through multiple comparisons of experimental results, the method overcame multiple shortcomings of traditional bacterial chemotaxis methods. The method reduced the error of plate counting and shortened the experimental cycle. For the identification of chemoattractant substances, this new method can save 2-3 days compared to the traditional method. Additionally, this method allows any researcher to systematically complete a bacterial chemotaxis experiment within 1-2 days. The protocol can be considered a valuable resource for understanding plant-microbe interactions.

Here, we present an improved chemotaxis assay protocol. The goal of this protocol is to reduce the steps and costs of traditional bacterial chemotaxis methods and to serve as a valuable resource for understanding plant-microbe interactions.

Chemotaxis identification is very important for the research and application of rhizosphere growth-promoting bacteria. We established a straightforward ...

Quantifying Cell Death Initiation Through Continuous Imaging

Studying Cell Death Initiation Using a Digital Microscope

Hypersensitive response (HR)-conferred resistance is an effective defense response that can be determined by the N resistance genes. HR is manifested as the formation of cell death zones on inoculated leaves. Here, a protocol for studying the rate of cell death initiation by imaging inoculated leaves in the time between the cell death initiation and the cell death appearance using a digital microscope is presented. The digital microscope enables a continuous imaging process in desired intervals, which allows an accurate determination of cell death initiation rate up to minutes exactly, as opposed to hours in traditional methods. Imaging with the digital microscope is also independent of light and can therefore be used during day and night without disturbing the circadian rhythm of the plant. Different pathosystems resulting in programmed cell death development could be studied using this protocol with minor modifications. Overall, the protocol thus allows simple, accurate, and inexpensive identification of cell death initiation rate.

Author Spotlight: A Streamlined Approach to Studying Cell Death Initiation in Hypersensitive Response 

Here we present a protocol for studying the rate of programmed cell death initiation by continuously imaging inoculated leaves following cell death induction.

Hypersensitive response (HR)-conferred resistance is an effective defense response that can be determined by the N resistance genes. HR is manifested as ...