The authors thank Greyson Butler and Margaret Barrett for help in carrying out the experiments, Judy Stone for advice on grain homogenization, and Lynn Hannum for advice on fluorometry. This work was supported by the National Science Foundation (IOB 0443676), by an Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health under grant number P20GM0103423, and by grants from the Colby College Division of Natural Sciences.

1. Preparation of Effector and Reporter Gene Constructs
<ol>
	<li>Build effector constructs that employ a constitutive promoter (e.g. maize ubiquitin, UBI) to drive expression from a desired open reading frame. For example, construct a plasmid containing UBI::TaABF1 to drive strong constitutive expression of TaABF15.</li>
	<li>Build reporter constructs that include the promoter whose activity is to be measured, placed upstream of an open reading frame, such as GUS. For example, construct a plasmid containing HVA1::GUS to measure expression from the HVA1 promoter2,5.</li>
	<li>Build an internal control construct (e.g. UBI::luciferase).</li>
	<li>Using a silica binding column protocol (see Table of Materials), prepare high-quality plasmid for each of the required gene constructs. Using ultraviolet spectroscopy (see Table of Materials), carefully measure the concentration of each plasmid preparation.</li>
</ol>
2. Preparation of Barley Grains for Bombardment
<ol>
	<li>Set up a spreadsheet (see Figure 1 for an example) indicating the plasmids that will be bombarded, the appropriate hormone treatments, and other relevant information for each treatment that will be part of the experiment.</li>
	<li>Using a cutting board and a sterile razor blade, cut off the embryos from grains of Himalaya barley (40 for each treatment included in the experiment). Exclude grains that are discolored or substantially smaller than average.</li>
	<li>Place all the embryoless grains into a 50 mL tube. Add 40 mL of water and rock for 10 minutes.</li>
	<li>Pour out the water carefully (to avoid losing grains) and add 40 mL of 10% bleach. Rock for 20 minutes.</li>
	<li>Pour out the bleach and add 40 mL of sterile water. Rock for 5 minutes. Repeat this sterile water wash four more times.</li>
	<li>Add 40 mL of Imbibing Solution (20 mM sodium succinate, 20 mM calcium chloride, pH 5.0) and 40 &#956;L of chloramphenicol stock solution (10 mg/mL).</li>
	<li>Transfer most of the Imbibing Solution (with chloramphenicol) from the tube into a Vermiculite Plate (see Table of Materials). Then transfer the grains onto the surface of the wet filter paper in the Vermiculite Plate. Spread out the grains evenly. Pour in enough imbibing solution to keep the grains partially (but not completely) submerged. Place the lid on top of the Vermiculite Plate.</li>
	<li>Incubate the embryoless grains at 24 &#176;C for about 48 h with fluorescent lighting. Add additional Imbibing Solution as necessary.</li>
	<li>Open up a 90 mm plastic petri dish and pour 20 mL of Imbibing Solution into the dish itself and 20 mL into the inverted lid. Add 20 &#956;L of chloramphenicol (10 mg/mL) to each. Sterilize two pairs of fine point forceps by dipping them in alcohol.</li>
	<li>Place a few of the embryoless grains into the lid of the petri dish. Using the forceps, gently remove the (transparent) seed coat from each grain. While removing the seed coat from the smooth side of the grain, do not damage the underlying (aleurone) cells. Transfer the peeled grain to the petri dish containing Imbibing Solution.</li>
	<li>After peeling the seed coat from all of the grains, return them to the Vermiculite Plate. Incubate the peeled embryoless grains at 24 &#176;C for 16 - 20 hours.</li>
	<li>Just before using the grains for bombardment, remove surface moisture by shaking them between filter papers in a petri dish.</li>
</ol>
3. Preparation of Plasmid DNA for Bombardment
<ol>
	<li>Label a 1.5 mL tube for each treatment that will be included in the bombardment experiment. To each tube add 2.5 &#181;g of UBI::luciferase internal control plasmid, 2.5 &#181;g of a GUS reporter plasmid, and the desired amount (typically 0.025 &#181;g to 2.5 &#181;g) of an effector plasmid. Add water to bring the total volume to 5 &#181;L.</li>
	<li>Prepare 1.6 &#181;m gold microcarriers (see Table of Materials) following published protocols6.</li>
	<li>For each treatment, add 50 &#181;L of suspended microcarriers into the 1.5 mL tube containing plasmid DNA. Coat the microcarriers with plasmid DNA according to manufacturer&#39;s protocols6.</li>
	<li>At the final step, when the plasmid-coated microcarriers are suspended in 48 &#181;L 100% ethanol, pipet 8 &#956;L of suspended microcarriers onto each of five macrocarriers and allow them to air dry.</li>
</ol>
4. Particle Bombardment of Embryoless Barley Grains
<ol>
	<li>Set up the particle bombardment apparatus (see Table of Materials)6.</li>
	<li>Place a 1550 psi rupture disk into the retaining cap and mount it on the instrument.</li>
	<li>Place a macrocarrier containing the desired plasmid combination (together with a stopping screen) into the microcarrier launch assembly. Insert the assembly into the top slot of the bombardment chamber. Set the distance between the rupture disc retaining cap and the macrocarrier cover lid at the standard distance (6 mm), and place the stopping screen support at the (standard) middle position, allowing a macrocarrier travel distance of 11 mm (Figure 2A).</li>
	<li>Arrange 8 embryoless grains in a tight radial pattern (with the thinner ends pointing inward) on a filter paper circle that is taped down flat to the lid of a 90 mm petri dish (see Figure 2B).</li>
	<li>Place the dish with the grains into the bombardment chamber, at a distance of 6 cm from the stopping screen.</li>
	<li>Evacuate the bombardment chamber to 95 kPa and then bombard the sample.</li>
	<li>After releasing the vacuum, transfer the bombarded grains to a labeled 60 mm petri dish containing 4 mL of Imbibing Solution containing 1 mg/ml of chloramphenicol.</li>
	<li>Repeat until all of the bombardments have been completed. Incubate (on a shaking platform at 100 rpm) at 24 &#176;C for 24 hours.</li>
</ol>
5. Extraction of Soluble Protein from the Bombarded Grains
<ol>
	<li>Using forceps, remove the 8 bombarded grains from a 60 mm petri dish and blot them dry on a paper towel. Divide the grains into two labeled 2.0 mL tubes (4 grains per tube) each containing 800 &#956;L Grinding Buffer (100 mM Na phosphate pH 7.2, 5 mM DTT, 10 &#181;g/mL leupeptin, 20% glycerol) and a 5 mm stainless steel bead. Repeat this process for all of bombarded grains.</li>
	<li>Place (up to 48) 2.0 mL tubes into the two racks of the bead homogenizer (see Table of Materials). Mount the racks on the homogenizer.</li>
	<li>Shake the samples at 30 Hz for 3 minutes.</li>
	<li>Remove the homogenizer racks from the homogenizer and place them on ice (5 min) to re-cool the samples.</li>
	<li>Mount the racks back on the homogenizer - in the opposite orientation. Shake the samples again at 30 Hz for 3 minutes.</li>
	<li>Cool the racks on ice, then repeat Steps 5.3 to 5.5. This will add up to a total of 12 minutes of shaking.</li>
	<li>Centrifuge the grain extracts at 16,000 x g at 4 &#176;C for 10 minutes.</li>
	<li>Immediately after the centrifugation, decant the clear supernatants into a second set of microcentrifuge tubes. Give each tube a quick vortex. Store the tubes on ice.</li>
	<li>After transferring the supernatant, recover the steel beads from the pellets so they can be washed and reused.</li>
</ol>
6. Measurement of Luciferase Activity from Grain Extracts
<ol>
	<li>For each tube of grain extract to be assayed, prepare a 12 mm x 75 mm glass test tube containing 200 &#956;L of Luciferase Assay Mixture (45 mM Tris sulfate pH 7.7, 15 mM MgCl2, 20 mM DTT, 1.5 mM EDTA, 1 mM luciferin, 1 mM ATP).</li>
	<li>Add 100 &#956;L of the first grain extract to the first assay tube. Vortex quickly to mix well. Immediately place the tube into the tube holder of the luminometer and close the door. When the measurement is finished, remove the tube from the luminometer &#8211; leaving the door open for placement of the next tube.</li>
	<li>Repeat this process until all the samples have been measured.</li>
</ol>
7. Measurement of GUS Activity from Grain Extracts
<ol>
	<li>Add 200 &#956;L of GUS Assay Buffer (50 mM Na phosphate pH 7.2, 2.5 mM 4-methylumbelliferyl--D-glucuronide, 10 mM DTT, 2 mM EDTA, 10 &#181;g/mL leupeptin, 20% methanol, 0.02% sodium azide) to each well of a 96 well plate.</li>
	<li>Place 50 &#956;L of each grain extract into the corresponding well. Mix with the tip after adding. Seal the top with sealing film.</li>
	<li>Incubate the 96 well plate at 37 &#176;C in the dark for 20 hours.</li>
	<li>Centrifuge the 96 well plate at 4,000 x g at 4 &#176;C for 10 minutes and place it on ice.</li>
	<li>Add 250 &#956;L of 0.2 M Na2CO3 to each well of a black 96 well plate.</li>
	<li>Add 6.25 &#956;L of each centrifuged GUS assay mixture into the corresponding well (containing 0.2 M Na2CO3) of the black 96 well plate. Mix with the tip after adding. Include wells with 6.25 &#956;L of 10 &#956;M, 40 &#956;M, and 100 &#956;M 4-methylumbelliferone as standards.</li>
	<li>Place the black plate into a plate fluorometer and read the fluorescence of methylumbelliferone. Take the readings at an excitation wavelength of 360 nm, and an emission wavelength of 460 nm. Set the gain of the instrument such that a well containing 6.25 &#956;L of 40 &#956;M 4-methylumbelliferone and 250 &#956;L of 0.2 M Na2CO3 gives a reading of 1000 fluorescence units.</li>
</ol>
8. Data Analysis
<ol>
	<li>Enter the values for the luciferase and GUS assays into a spreadsheet. Exclude from consideration any sample with a luciferase reading of lower than 20,000 relative luminescence units s-1, as this indicates that the gene constructs were not successfully delivered to the aleurone cells.</li>
	<li>For each successfully bombarded grain extract (representing a group of four embryoless grains), calculate the normalized GUS expression from the raw GUS and luciferase data as follows: normalized GUS = [(GUS expression - GUS blank) x (2,000,000)] / (luciferase expression &#8211; luciferase blank). 
	NOTE: This normalizes the amount of GUS activity to what would have been observed in a bombardment that gave a luciferase reading of 2,000,000.</li>
	<li>Report the relative level of expression of a particular reporter construct in the presence of effector constructs or hormone treatments being tested by comparing to the level of expression in the absence of effectors or hormones.</li>
</ol>

<ol>
	<li>Chen, K., An, Y. Q. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transcriptional+responses+to+gibberellin+and+abscisic+acid+in+barley+aleurone.">Transcriptional responses to gibberellin and abscisic acid in barley aleurone.</a> J. Integ. Plant Biol. 48, 591-612 (2006).</li><li>Lanahan, M. B., Ho, T. H. D., Rogers, S. W., Rogers, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+gibberellin+response+complex+in+cereal+alpha-amylase+gene+promoters.">A gibberellin response complex in cereal alpha-amylase gene promoters.</a> Plant Cell. 4, 203-211 (1992).</li><li>Shen, Q., Zhang, P., Ho, T. H. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modular+nature+of+abscisic+acid+(ABA)+response+complexes;+composite+promoter+units+that+are+necessary+and+sufficient+for+ABA+induction+of+gene+expression.">Modular nature of abscisic acid (ABA) response complexes; composite promoter units that are necessary and sufficient for ABA induction of gene expression.</a> Plant Cell. 8, 1107-1119 (1996).</li><li>G&#243;mez-Cadenas, A., Zentella, R., Walker-Simmons, M. K., Ho, T. H. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gibberellin/abscisic+acid+antagonism+in+barley+aleurone+cells:+site+of+action+of+the+protein+kinase+PKABA1+in+relation+to+gibberellin+signaling+molecules.">Gibberellin/abscisic acid antagonism in barley aleurone cells: site of action of the protein kinase PKABA1 in relation to gibberellin signaling molecules.</a> Plant Cell. 13, 667-679 (2001).</li><li>Johnson, R. R., Shin, M., Shen, J. Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+wheat+PKABA1-interacting+factor+TaABF1+mediates+both+abscisic+acid-suppressed+and+abscisic+acid-induced+gene+expression+in+bombarded+aleurone+cells.">The wheat PKABA1-interacting factor TaABF1 mediates both abscisic acid-suppressed and abscisic acid-induced gene expression in bombarded aleurone cells.</a> Plant Mol. Biol. 68, 93-103 (2008).</li><li>Harris, L. J., Martinez, S. A., Keyser, B. R., Dyer, W. E., Johnson, R. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+analysis+of+TaABF1+during+abscisic+acid+and+gibberellin+signaling+in+aleurone+cells+of+cereal+grains.">Functional analysis of TaABF1 during abscisic acid and gibberellin signaling in aleurone cells of cereal grains.</a> Seed Science Res. 23, 89-98 (2013).</li><li>Shen, Q., Casaretto, J., Zhang, P., Ho, T. H. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+definition+of+ABA-response+complexes:+the+promoter+units+necessary+and+sufficient+for+ABA+induction+of+gene+expression+in+barley+(Hordeum+vulgare).">Functional definition of ABA-response complexes: the promoter units necessary and sufficient for ABA induction of gene expression in barley (Hordeum vulgare).</a> Plant Mol. Biol. 54, 111-124 (2004).</li><li>Ritchie, S., Gilroy, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Abscisic+acid+signal+transduction+in+the+barley+aleurone+is+mediated+by+phospholipase+D+activity.">Abscisic acid signal transduction in the barley aleurone is mediated by phospholipase D activity.</a> Proc. Natl. Acad. Sci. USA. 95, 2697-2702 (1998).</li><li>Takemiya, A., Shimazaki, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phosphatidic+acid+inhibits+blue+light-induced+stomatal+opening+via+inhibition+of+protein+phosphatase+1.">Phosphatidic acid inhibits blue light-induced stomatal opening via inhibition of protein phosphatase 1.</a> Plant Physiol. 153, 1555-1562 (2010).</li><li>Zou, X., Seeman, J. R., Neuman, D., Shen, Q. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+WRKY+gene+from+creosote+bush+encodes+an+activator+of+the+abscisic+acid+signaling+pathway.">A WRKY gene from creosote bush encodes an activator of the abscisic acid signaling pathway.</a> J. Biol. Chem. 279, 55770-55779 (2004).</li><li>Ishibashi, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reactive+oxygen+species+are+involved+in+gibberellin/abscisic+acid+signaling+in+barley+aleurone+cells.">Reactive oxygen species are involved in gibberellin/abscisic acid signaling in barley aleurone cells.</a> Plant Physiol. 158, 1705-1714 (2012).</li><li>Piskurewicz, U., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+gibberellic+acid+signaling+repressor+RGL2+inhibits+Arabidopsis+seed+germination+by+stimulating+abscisic+acid+synthesis+and+ABI5+activity.">The gibberellic acid signaling repressor RGL2 inhibits Arabidopsis seed germination by stimulating abscisic acid synthesis and ABI5 activity.</a> Plant Cell. 20, 2729-2745 (2008).</li><li>Hong, J. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phosphorylation-mediated+regulation+of+a+rice+ABA+responsive+element+binding+factor.">Phosphorylation-mediated regulation of a rice ABA responsive element binding factor.</a> Phytochemistry. 72, 27-36 (2011).</li><li>Lopez-Molina, L., Mongrand, S., McLachlin, D. T., Chait, B. T., Chua, N. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ABI5+acts+downstream+of+ABI3+to+execute+an+ABA-dependent+growth+arrest+during+germination.">ABI5 acts downstream of ABI3 to execute an ABA-dependent growth arrest during germination.</a> Plant J. 32, 317-328 (2002).</li><li>Zhou, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=SOS2-LIKE+PROTEIN+KINASE5,+an+SNF1-RELATED+PROTEIN+KINASE3-Type+protein+kinase,+is+important+for+abscisic+acid+responses+in+Arabidopsis+through+phosphorylation+of+ABSCISIC+ACID-INSESENSITIVE5.">SOS2-LIKE PROTEIN KINASE5, an SNF1-RELATED PROTEIN KINASE3-Type protein kinase, is important for abscisic acid responses in Arabidopsis through phosphorylation of ABSCISIC ACID-INSESENSITIVE5.</a> Plant Physiol. 168, 659-676 (2015).</li><li>Zong, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Feedback+regulation+of+ABA+signaling+and+biosynthesis+by+a+bZIP+transcription+factor+targets+drought-resistance-related+genes.">Feedback regulation of ABA signaling and biosynthesis by a bZIP transcription factor targets drought-resistance-related genes.</a> Plant Physiol. 171, 2810-2825 (2016).</li></ol>

The authors have nothing to disclose.

The introduction of effector gene constructs via particle bombardment, followed by transient expression of reporter constructs is a valuable strategy for dissecting the role of particular actors in GA/ABA signaling and in the resulting hormone-regulated gene expression. 
However, existing protocols for carrying out such experiments in barley aleurone cells2,3,4,5,<sup class="xre...

The barley aleurone layer is a well-established model system for the study of hormone-regulated gene expression in plants1. In particular, a number of genes required for germination or early seedling development are activated by gibberellin (GA), while genes associated with stress responses are activated by abscisic acid (ABA). The GA and ABA signaling pathways are intertwined, as the expression of some GA-activated genes is inhibited by ABA, and vice-versa1.
A valuable strategy for understanding the role of particular actors in GA/ABA signaling has been the introduction of effector gene constructs via particle bombardment, followed by transient expression of reporter constructs that allow the resulting effect on downstream gene expression to be determined. The use of reporter genes such as GUS&#160;(&#946;-glucuronidase) or Luciferase allows the sensitive and quantitative measurement of gene expression specifically within the cells that have received the effector construct. For example, the introduction of an effector construct encoding the transcription factor TaABF15,6 established that ABA-induced genes such as HVA1 are induced by TaABF1, while GA-induced genes such as Amy32b are repressed. Particle bombardment as an experimental strategy has been used by multiple laboratories to investigate diverse aspects of GA/ABA signaling. Such work has led to the identification of promoter elements important for the activation of both GA-induced2 and ABA-induced genes3, and to the discovery of protein kinases4 and transcription factors5 that regulate the expression of these genes.
The existing protocols2,3,4,5,6 for particle bombardment and subsequent measurement of transient gene expression are quite labor intensive, as each set of bombarded barely grains is homogenized by hand in a mortar and pestle and the enzyme assays are carried out individually. This manuscript reports an improved protocol that partially automates and streamlines the homogenization step and the GUS assays to allow significantly more throughput, permitting a larger number of treatments to be tested in the same experiment, and/or the inclusion of more replicates for each treatment to obtain more statistically robust results. Representative results are shown for the expression of HVA1 and Amy32b reporter constructs, regulated by the transcription factor TaABF1 as well as by GA, ABA, and other regulatory molecules.

<table>
	<tbody>
		<tr>
			<td>GeneElute HP plasmid Maxiprep kit</td>
			<td>Sigma</td>
			<td>NA0310-1KT</td>
			<td></td>
		</tr>
		<tr>
			<td>UV-vis spectrophotometer</td>
			<td>Nanodrop</td>
			<td>ND-1000</td>
			<td></td>
		</tr>
		<tr>
			<td>Himalaya barley grains</td>
			<td>/</td>
			<td>/</td>
			<td>A variety of hulless barley (store in the dark at 4&#176; C)</td>
		</tr>
		<tr>
			<td>sodium succinate</td>
			<td>Sigma</td>
			<td>S2378</td>
			<td>Reagent for Imbibing Solution</td>
		</tr>
		<tr>
			<td>calcium chloride (dihydrate)</td>
			<td>Fisher</td>
			<td>C79-500</td>
			<td>Reagent for Imbibing Solution</td>
		</tr>
		<tr>
			<td>Imbibing Solution</td>
			<td>home made</td>
			<td>/</td>
			<td>20 mM sodium succinate, 20 mM calcium chloride, pH 5.0. Sterilize by autoclaving before use.</td>
		</tr>
		<tr>
			<td>chloramphenicol</td>
			<td>Sigma</td>
			<td>C0378</td>
			<td>Prepare a 10 mg/mL stock solution in 70% ethanol.</td>
		</tr>
		<tr>
			<td>vermiculite</td>
			<td>Fisher</td>
			<td>NC0430369</td>
			<td>Used for vermiculite plates.</td>
		</tr>
		<tr>
			<td>filter paper circles (90 mm)</td>
			<td>Whatman</td>
			<td>1001 090</td>
			<td>Used for vermiculite and for pre-bombardment grain preparation</td>
		</tr>
		<tr>
			<td>Vermiculite Plates</td>
			<td>home made</td>
			<td>/</td>
			<td>Add 50 mL of vermiculite to a glass petri dish. Place a 90 mm paper circle on top of the vermiculite. Autoclave.</td>
		</tr>
		<tr>
			<td>forceps (fine pointed)</td>
			<td>Fisher</td>
			<td>13-812-42</td>
			<td>Used for removing seed coat from barley grains.</td>
		</tr>
		<tr>
			<td>forceps (ultra fine point)</td>
			<td>Fisher</td>
			<td>12-000-122</td>
			<td>Used for removing seed coat from barley grains.</td>
		</tr>
		<tr>
			<td>gold microcarriers (1.6 &#956;m)</td>
			<td>BioRad</td>
			<td>1652264</td>
			<td></td>
		</tr>
		<tr>
			<td>macrocarriers</td>
			<td>BioRad</td>
			<td>1652335</td>
			<td></td>
		</tr>
		<tr>
			<td>calcium chloride (dihydrate)</td>
			<td>Fisher</td>
			<td>C79-500</td>
			<td>Prepare a 2.5 M stock solution and store 1 mL aliquots at -20&#176; C.</td>
		</tr>
		<tr>
			<td>spermidine</td>
			<td>Sigma</td>
			<td>S0266</td>
			<td>Prepare a 100 mM stock solution and store 500 &#956;L aliquots at -20&#176; C (use within 2 months).</td>
		</tr>
		<tr>
			<td>rupture discs (1550 psi)</td>
			<td>BioRad</td>
			<td>1652331</td>
			<td></td>
		</tr>
		<tr>
			<td>stopping screens</td>
			<td>BioRad</td>
			<td>1652336</td>
			<td></td>
		</tr>
		<tr>
			<td>macrocarrier holders</td>
			<td>BioRad</td>
			<td>1652322</td>
			<td></td>
		</tr>
		<tr>
			<td>Biolistic particle delivery system</td>
			<td>BioRad</td>
			<td>PDS-1000/He</td>
			<td></td>
		</tr>
		<tr>
			<td>sodium phosphate monobasic monohydrate</td>
			<td>Sigma</td>
			<td>S9638</td>
			<td>Reagent for 1M sodium phosphate pH 7.2</td>
		</tr>
		<tr>
			<td>sodium phosphate dibasic</td>
			<td>Sigma</td>
			<td>S9763</td>
			<td>Reagent for 1M sodium phosphate pH 7.2</td>
		</tr>
		<tr>
			<td>1M sodium phosphate pH 7.2</td>
			<td>home made</td>
			<td>/</td>
			<td>Combine 6.9 g of sodium phosphate monobasic monohydrate with 7.1 g of sodium phosphate dibasic. Add water to 100 mL. Add NaOH to get pH 7.2.</td>
		</tr>
		<tr>
			<td>dithiothrietol (DTT)</td>
			<td>Sigma</td>
			<td>43819</td>
			<td>Dissolve in water to 1 M. Store at -20&#176; in 1 mL aliquots.</td>
		</tr>
		<tr>
			<td>leupeptin</td>
			<td>Sigma</td>
			<td>L2884</td>
			<td>Dissolve in water to 10 mg/mL. Store at -20&#176; C.</td>
		</tr>
		<tr>
			<td>glycerol</td>
			<td>Sigma</td>
			<td>G5516</td>
			<td>Prepare a 50% solution in water.</td>
		</tr>
		<tr>
			<td>Grinding Buffer</td>
			<td>home made</td>
			<td>/</td>
			<td>Combine 10 mL of 1 M sodium phosphate pH 7.2, 500 &#956;L of 1 M DTT, 100 &#956;L of 10 mg/mL leupeptin, and 40 mL of 50% glycerol. Add water to 100 mL.</td>
		</tr>
		<tr>
			<td>stainlesss steel beads (5 mm)</td>
			<td>Qiagen</td>
			<td>69989</td>
			<td></td>
		</tr>
		<tr>
			<td>2.0 mL tubes</td>
			<td>Eppendorf</td>
			<td>22363352</td>
			<td>This specific model of tube is recommended for use with the homogenizer.</td>
		</tr>
		<tr>
			<td>bead homogenizer (TissueLyser)</td>
			<td>Qiagen</td>
			<td>85210</td>
			<td></td>
		</tr>
		<tr>
			<td>12mm x 75 mm glass test tubes</td>
			<td>Fisher</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>luciferin</td>
			<td>Goldbio</td>
			<td>LUCK-100</td>
			<td>Prepare a 25 mM stock solution and store 1 mL aliquots at -20&#176; C.</td>
		</tr>
		<tr>
			<td>ATP</td>
			<td>Sigma</td>
			<td>A7699</td>
			<td>Prepare a 100 mM stock solution and store 250 &#956;L aliquots at -20&#176; C.</td>
		</tr>
		<tr>
			<td>Tris base</td>
			<td>Sigma</td>
			<td>T1503</td>
			<td>Reagent for 1M Tris sulfate pH 7.7.</td>
		</tr>
		<tr>
			<td>sulfuric acid</td>
			<td>Sigma</td>
			<td>258105</td>
			<td>Reagent for 1M Tris sulfate pH 7.7.</td>
		</tr>
		<tr>
			<td>1M Tris sulfate pH 7.7</td>
			<td>home made</td>
			<td>/</td>
			<td>Dissolve 12.1 g Tris base in 100 mL of water. Adjust pH to 7.7 with sulfuric acid.</td>
		</tr>
		<tr>
			<td>magnesium chloride</td>
			<td>Sigma</td>
			<td>M9397</td>
			<td>Dissolve in water to 2 M.</td>
		</tr>
		<tr>
			<td>Luciferase Assay Buffer (LAB)</td>
			<td>home made</td>
			<td>/</td>
			<td>Combine 3 mL of 1 M Tris sulfate pH 7.7, 500 &#956;L of 2 M magnesium chloride, 1 mL of 1 M DTT, and 200 &#956;L of 0.5 M EDTA. Add water to 50 mL.</td>
		</tr>
		<tr>
			<td>Luciferase Assay Mixture</td>
			<td>home made</td>
			<td>/</td>
			<td>Combine 15 mL of LAB, 800 &#956;L of 25 mM luciferin, 200 &#956;L of 100 mM ATP, and 4 mL of water. This makes enough assay mixture (20 mL) for 100 luciferase assays.</td>
		</tr>
		<tr>
			<td>luminometer (Sirius)</td>
			<td>Berthold</td>
			<td>/</td>
			<td></td>
		</tr>
		<tr>
			<td>4-methylumbelliferyl-&#946;-D-glucuronide (MUG)</td>
			<td>Goldbio</td>
			<td>MUG1</td>
			<td>Dissolve in DMSO to 100 mM.</td>
		</tr>
		<tr>
			<td>sodium azide</td>
			<td>Sigma</td>
			<td>S8032</td>
			<td>Prepare a 2% stock solution in water and store 1 mL aliquots at -20&#176; C.</td>
		</tr>
		<tr>
			<td>96 well plates (standard)</td>
			<td>Fisher</td>
			<td>12565501</td>
			<td></td>
		</tr>
		<tr>
			<td>GUS assay buffer</td>
			<td>home made</td>
			<td>/</td>
			<td>Combine 2.5 mL of MUG, 5 mL of 1 M sodium phosphate pH 7.2, 400 &#956;L of 0.5 M EDTA, 1 mL of 1 M DTT, 100 &#956;L of 10 mg/ml leupeptin, 20 mL of methanol, and 1 mL of 2% sodium azide. Add water to 100 mL.</td>
		</tr>
		<tr>
			<td>TempPlate sealing film</td>
			<td>USA Scientific</td>
			<td>2921-1000</td>
			<td></td>
		</tr>
		<tr>
			<td>96 well plates (black)</td>
			<td>Costar</td>
			<td>3916</td>
			<td></td>
		</tr>
		<tr>
			<td>sodium carbonate</td>
			<td>Sigma</td>
			<td>S7795</td>
			<td>Prepare a 200 mM solution in water.</td>
		</tr>
		<tr>
			<td>4-methylumbelliferone</td>
			<td>Sigma</td>
			<td>M1381</td>
			<td>Prepare a 100 &#956;M solution in water. Freeze 1 mL aliquots at -20&#176; C.</td>
		</tr>
		<tr>
			<td>microplate fluouresence reader</td>
			<td>Bio-Tek</td>
			<td>FLX-800</td>
			<td></td>
		</tr>
	</tbody>
</table>

measuring gene expression in bombarded barley aleurone layers with increased throughput

The aleurone layer of barley grains is an important model system for hormone-regulated gene expression in plants. In aleurone cells, genes required for germination or early seedling development are activated by gibberellin (GA), while genes associated with stress responses are activated by abscisic acid (ABA). The mechanisms of GA and ABA signaling can be interrogated by introducing reporter gene constructs into aleurone cells via particle bombardment, with the resulting transient expression measured using enzyme assays. An improved protocol is reported that partially automates and streamlines the grain homogenization step and the enzyme assays, allowing significantly more throughput than existing methods. Homogenization of the grain samples is carried out using an automated tissue homogenizer, and GUS (&#946;-glucuronidase) assays are carried out using a 96-well plate system. Representative results using the protocol suggest that phospholipase D activity may play an important role in the activation of HVA1 gene expression by ABA, through the transcription factor TaABF1.

The technique described here can be used to introduce any test gene construct into aleurone cells of barley grains. The level of expression from the test gene may then be conveniently measured (Figure 2). The higher throughput protocol described here greatly increases the efficiency of the seed grinding and enzyme assay steps. This method has been used to assess the ability of the transcription factor TaABF15,<sup class="xre...

Watch this Scientific Journal Video about Measuring Gene Expression in Bombarded Barley Aleurone Layers with Increased Throughput at JoVE.com

Measuring Gene Expression in Bombarded Barley Aleurone Layers with Increased Throughput

An improved protocol is presented for the measurement of transient gene expression from reporter constructs in barley aleurone cells after particle bombardment. The combination of automated grain grinding with 96-well plate enzyme assays provides high throughput for the procedure.

The aleurone layer of barley grains is an important model system for hormone-regulated gene expression in plants. In aleurone cells, genes required for ...

measuring-gene-expression-bombarded-barley-aleurone-layers-with

Research

JoVE Journal

Genetics

6.4K Views.  Colby College. An improved protocol is presented for the measurement of transient gene expression from reporter constructs in barley aleurone cells after particle bombardment. The combination of automated grain grinding with 96-well plate enzyme assays provides high throughput for the procedure.

Video: Measuring Gene Expression in Bombarded Barley Aleurone Layers with Increased Throughput

Parallel Measurement of Circadian Clock Gene Expression and Hormone Secretion in Human Primary Cell Cultures

Circadian clocks are functional in all light-sensitive organisms, allowing for an adaptation to the external world by anticipating daily environmental changes. Considerable progress in our understanding of the tight connection between the circadian clock and most aspects of physiology has been made in the field over the last decade. However, unraveling the molecular basis that underlies the function of the circadian oscillator in humans stays of highest technical challenge. Here, we provide a detailed description of an experimental approach for long-term (2-5 days) bioluminescence recording and outflow medium collection in cultured human primary cells. For this purpose, we have transduced primary cells with a lentiviral luciferase reporter that is under control of a core clock gene promoter, which allows for the parallel assessment of hormone secretion and circadian bioluminescence. Furthermore, we describe the conditions for disrupting the circadian clock in primary human cells by transfecting siRNA targeting CLOCK. Our results on the circadian regulation of insulin secretion by human pancreatic islets, and myokine secretion by human skeletal muscle cells, are presented here to illustrate the application of this methodology. These settings can be used to study the molecular makeup of human peripheral clocks and to analyze their functional impact on primary cells under physiological or pathophysiological conditions.

Here, we describe settings to monitor in parallel circadian bioluminescence and the secretory activity of human islet cells and primary myotubes. For this, we employed lentiviral gene delivery of a luciferase core clock reporter, followed by in vitro synchronization and collection of outflow medium by continuous cell perifusion.

Circadian clocks are functional in all light-sensitive organisms, allowing for an adaptation to the external world by anticipating daily environmental ...

Perturbations of Circulating miRNAs in Irritable Bowel Syndrome Detected Using a Multiplexed High-throughput Gene Expression Platform

The gene expression platform assay allows for robust and highly reproducible quantification of the expression of up to 800 transcripts (mRNA or miRNAs) in a single reaction. The miRNA assay counts transcripts by directly imaging and digitally counting miRNA molecules that are labeled with color-coded fluorescent barcoded probe sets (a reporter probe and a capture probe). Barcodes are hybridized directly to mature miRNAs that have been elongated by ligating a unique oligonucleotide tag (miRtag) to the 3&#39; end. Reverse transcription and amplification of the transcripts are not required. Reporter probes contain a sequence of six color positions populated using a combination of four fluorescent colors. The four colors over six positions are used to construct a gene-specific color barcode sequence. Post-hybridization processing is automated on a robotic prep station. After hybridization, the excess probes are washed away, and the tripartite structures (capture probe-miRNA-reporter probe) are fixed to a streptavidin-coated slide via the biotin-labeled capture probe. Imaging and barcode counting is done using a digital analyzer. The immobilized barcoded miRNAs are visualized and imaged using a microscope and camera, and the unique barcodes are decoded and counted. Data quality control (QC), normalization, and analysis are facilitated by a custom-designed data processing and analysis software that accompanies the assay software. The assay demonstrates high linearity over a broad range of expression, as well as high sensitivity. Sample and assay preparation does not involve enzymatic reactions, reverse transcription, or amplification; has few steps; and is largely automated, reducing investigator effects and resulting in high consistency and technical reproducibility. Here, we describe the application of this technology to identifying circulating miRNA perturbations in irritable bowel syndrome.

We describe the use of a multiplexed high-throughput gene expression platform that quantitates gene expression by barcoding and counting molecules in biological substrates without the need for amplification. We used the platform to quantitate microRNA (miRNA) expression in whole blood in subjects with and without irritable bowel syndrome.

The gene expression platform assay allows for robust and highly reproducible quantification of the expression of up to 800 transcripts (mRNA or miRNAs) in ...

Rearing and Double-stranded RNA-mediated Gene Knockdown in the Hide Beetle, Dermestes maculatus

Advances in genomics have raised the possibility of probing biodiversity at an unprecedented scale. However, sequence alone will not be informative without tools to study gene function. The development and sharing of detailed protocols for the establishment of new model systems in laboratories, and for tools to carry out functional studies, is thus crucial for leveraging the power of genomics. Coleoptera (beetles) are the largest clade of insects and occupy virtually all types of habitats on the planet. In addition to providing ideal models for fundamental research, studies of beetles can have impacts on pest control as they are often pests of households, agriculture, and food industries. Detailed protocols for rearing and maintenance of D. maculatus laboratory colonies and for carrying out dsRNA-mediated interference in D. maculatus are presented. Both embryonic and parental RNAi procedures-including apparatus set up, preparation, injection, and post-injection recovery-are described. Methods are also presented for analyzing embryonic phenotypes, including viability, patterning defects in hatched larvae, and cuticle preparations for unhatched larvae. These assays, together with in situ hybridization and immunostaining for molecular markers, make D. maculatus an accessible model system for basic and applied research. They further provide useful information for establishing procedures in other emerging insect model systems.

Rearing and Double-stranded RNA-mediated Gene Knockdown in the Hide Beetle, Dermestes maculatus

Here, we present protocols for rearing an intermediate-germ beetle, Dermestes maculatus (D. maculatus) in the lab. We also share protocols for embryonic and parental RNAi and methods for analyzing embryonic phenotypes to study gene function in this species.

Advances in genomics have raised the possibility of probing biodiversity at an unprecedented scale. However, sequence alone will not be informative ...

Single-cell Gene Expression Profiling Using FACS and qPCR with Internal Standards

Gene expression measurements from bulk populations of cells can obscure the considerable transcriptomic variation of individual cells within those populations. Single-cell gene expression measurements can help assess the role of noise in gene expression, identify correlations in the expression of pairs of genes, and reveal subpopulations of cells that respond differently to a stimulus. Here, we describe a procedure to measure the expression of up to 96 genes in single mammalian cells isolated from a population growing in tissue culture. Cells are sorted into lysis buffer by fluorescence-activated cell sorting (FACS), and the mRNA species of interest are reverse-transcribed and amplified. Gene expression is then measured using a microfluidic real-time PCR machine, which performs up to 96 qPCR assays on up to 96 samples at a time. We also describe the generation and use of PCR amplicon standards to enable the estimation of the absolute number of each transcript. Compared with other methods of measuring gene expression in single cells, this approach allows for the quantification of more distinct transcripts than RNA FISH at a lower cost than RNA-Seq.

We describe a method to sort single mammalian cells and to quantify the expression of up to 96 target genes of interest in each cell. This method includes the use of internal qPCR standards to enable the estimation of absolute transcript counts.

Gene expression measurements from bulk populations of cells can obscure the considerable transcriptomic variation of individual cells within those ...

Studying Cell Cycle-regulated Gene Expression by Two Complementary Cell Synchronization Protocols

The gene expression program of the cell cycle represents a critical step for understanding cell cycle-dependent processes and their role in diseases such as cancer. Cell cycle-regulated gene expression analysis depends on cell synchronization into specific phases. Here we describe a method utilizing two complementary synchronization protocols that is commonly used for studying periodic variation of gene expression during the cell cycle. Both procedures are based on transiently blocking the cell cycle in one defined point. The synchronization protocol by hydroxyurea (HU) treatment leads to cellular arrest in late G1/early S phase, and release from HU-mediated arrest provides a cellular population uniformly progressing through S and G2/M. The synchronization protocol by thymidine and nocodazole (Thy-Noc) treatment blocks cells in early mitosis, and release from Thy-Noc mediated arrest provides a synchronized cellular population suitable for G1 phase and S phase-entry studies. Application of both procedures requires monitoring of the cell cycle distribution profiles, which is typically performed after propidium iodide (PI) staining of the cells and flow cytometry-mediated analysis of DNA content. We show that the combined use of two synchronization protocols is a robust approach to clearly determine the transcriptional profiles of genes that are differentially regulated in the cell cycle (i.e. E2F1 and E2F7), and consequently to have a better understanding of their role in cell cycle processes. Furthermore, we show that this approach is useful for the study of mechanisms underlying drug-based therapies (i.e. mitomycin C, an anticancer agent), because it allows to discriminate genes that are responsive to the genotoxic agent from those solely affected by cell cycle perturbations imposed by the agent.

We report two cell synchronization protocols that provide a context for studying events related to specific phases of the cell cycle. We show that this approach is useful for analyzing the regulation of specific genes in an unperturbed cell cycle or upon exposure to agents affecting the cell cycle.

The gene expression program of the cell cycle represents a critical step for understanding cell cycle-dependent processes and their role in diseases such ...

Sample Preparation and Analysis of RNASeq-based Gene Expression Data from Zebrafish

The analysis of global gene expression changes is a valuable tool for identifying novel pathways underlying observed phenotypes. The zebrafish is an excellent model for rapid assessment of whole transcriptome from whole animal or individual cell populations due to the ease of isolation of RNA from large numbers of animals. Here a protocol for global gene expression analysis in zebrafish embryos using RNA sequencing (RNASeq) is presented. We describe preparation of RNA from whole embryos or from cell populations obtained using cell sorting in transgenic animals. We also describe an approach for analysis of RNASeq data to identify enriched pathways and Gene Ontology (GO) terms in global gene expression data sets. Finally, we provide a protocol for validation of gene expression changes using quantitative reverse transcriptase PCR (qRT-PCR). These protocols can be used for comparative analysis of control and experimental sets of zebrafish to identify novel gene expression changes, and provide molecular insight into phenotypes of interest.

This protocol presents an approach for whole transcriptome analysis from zebrafish embryos, larvae, or sorted cells. We include isolation of RNA, pathway analysis of RNASeq data, and qRT-PCR-based validation of gene expression changes.

The analysis of global gene expression changes is a valuable tool for identifying novel pathways underlying observed phenotypes. The zebrafish is an ...

Generation of a Gene-disrupted Streptococcus mutans Strain Without Gene Cloning

Typical methods for the elucidation of the function of a particular gene involve comparative phenotypic analyses of the wild-type strain and a strain in which the gene of interest has been disrupted. A gene-disruption DNA construct containing a suitable antibiotic resistance marker gene is useful for the generation of gene-disrupted strains in bacteria. However, conventional construction methods, which require gene cloning steps, involve complex and time-consuming protocols. Here, a relatively facile, rapid, and cost-effective method for targeted gene disruption in Streptococcus mutans is described. The method utilizes a 2-step fusion polymerase chain reaction (PCR) to generate the disruption construct and electroporation for genetic transformation. This method does not require an enzymatic reaction, other than PCR, and additionally offers greater flexibility in terms of the design of the disruption construct. Employment of electroporation facilitates the preparation of competent cells and improves the transformation efficiency. The present method may be adapted for the generation of gene-disrupted strains of various species.

Generation of a Gene-disrupted Streptococcus mutans Strain Without Gene Cloning

We describe a facile, rapid, and relatively inexpensive method for the generation of gene-disrupted Streptococcus mutans strains; this technique may be adapted for the generation of gene-disrupted strains of various species.

Typical methods for the elucidation of the function of a particular gene involve comparative phenotypic analyses of the wild-type strain and a strain in ...

An Optogenetic Method to Control and Analyze Gene Expression Patterns in Cell-to-cell Interactions

Cells should respond properly to temporally changing environments, which are influenced by various factors from surrounding cells. The Notch signaling pathway is one of such essential molecular machinery for cell-to-cell communications, which plays key roles in normal development of embryos. This pathway involves a cell-to-cell transfer of oscillatory information with ultradian rhythms, but despite the progress in molecular biology techniques, it has been challenging to elucidate the impact of multicellular interactions on oscillatory gene dynamics. Here, we present a protocol that permits optogenetic control and live monitoring of gene expression patterns in a precise temporal manner. This method successfully revealed that intracellular and intercellular periodic inputs of Notch signaling entrain intrinsic oscillations by frequency tuning and phase shifting at the single-cell resolution. This approach is applicable to the analysis of the dynamic features of various signaling pathways, providing a unique platform to test a functional significance of dynamic gene expression programs in multicellular systems.

Here, we present a protocol to analyze cell-to-cell transfer of oscillatory information by optogenetic control and live monitoring of gene expression. This approach provides a unique platform to test a functional significance of dynamic gene expression programs in multicellular systems.

Cells should respond properly to temporally changing environments, which are influenced by various factors from surrounding cells. The Notch signaling ...

An Ecdysone Receptor-based Singular Gene Switch for Deliberate Expression of Transgene with Robustness, Reversibility, and Negligible Leakiness

Precise control of transgene expression is desirable in biological and clinical studies. However, because the binary feature of currently employed gene switches requires the transfer of two therapeutic expression units concurrently into a single cell, the practical application of the system for gene therapy is limited. To simplify the transgene expression system, we generated a gene switch designated as pEUI(+) encompassing a complete set of transgene expression modules in a single vector. Comprising of the GAL4 DNA-binding domain and modified EcR (GvEcR), a minimal VP16 activation domain fused with a GAL4 DNA-binding domain, as well as a modified Drosophila ecdysone receptor (EcR), the newly developed singular gene switch is highly responsive to the administration of a chemical inducer in a time- and dosage-dependent manner. The pEUI(+) vector is a potentially powerful tool for improving the control of transgene expression in both biological research and pre-clinical studies. Here, we present a detailed protocol for modulation of a transient and stable transgene expression using pEUI(+) vector by the treatment of tebufenozide (Teb). Additionally, we share important guidelines for the use of Teb as a chemical inducer.

Here, we present a protocol for the modulation of transgene expression using pEUI(+) singular gene switch by tebufenozide treatment.

Precise control of transgene expression is desirable in biological and clinical studies. However, because the binary feature of currently employed gene ...

Exploring the Root Microbiome: Extracting Bacterial Community Data from the Soil, Rhizosphere, and Root Endosphere

The intimate interaction between plant host and associated microorganisms is crucial in determining plant fitness, and can foster improved tolerance to abiotic stresses and diseases. As the plant microbiome can be highly complex, low-cost, high-throughput methods such as amplicon-based sequencing of the 16S rRNA gene are often preferred for characterizing its microbial composition and diversity. However, the selection of appropriate methodology when conducting such experiments is critical for reducing biases that can make analysis and comparisons between samples and studies difficult. This protocol describes in detail a standardized methodology for the collection and extraction of DNA from soil, rhizosphere, and root samples. Additionally, we highlight a well-established 16S rRNA amplicon sequencing pipeline that allows for the exploration of the composition of bacterial communities in these samples, and can easily be adapted for other marker genes. This pipeline has been validated for a variety of plant species, including sorghum, maize, wheat, strawberry, and agave, and can help overcome issues associated with the contamination from plant organelles.

Here, we describe a protocol to obtain amplicon sequence data of soil, rhizosphere, and root endosphere microbiomes. This information can be used to investigate the composition and diversity of plant-associated microbial communities, and is suitable for the use with a wide range of plant species.

The intimate interaction between plant host and associated microorganisms is crucial in determining plant fitness, and can foster improved tolerance to ...