We thank all the members of the research project, &#39;Co-creation of plant adaptive traits via assembly of plant-microbe holobiont&#39;, for fruitful discussions. This work was supported by Grant-in-Aid for Transformative Research Areas (21H05151 and 21H05149 to A.M. and 21H05152 to Y.T.) and Grant-in-Aid for Challenging Exploratory Research (22K19178 to A. M.).

1. Growing plants
<ol>
	<li>To break dormancy, resuspend A. thaliana (Col-0) seeds in deionized water and incubate them at 4 &#176;C for 4 days in the dark.</li>
	<li>Sow the seeds on the soil and grow in a chamber equipped with white fluorescent light. Maintain the following growth conditions: temperature of 22 &#176;C, light intensity of 6,000 lux (ca. 100 &#181;mol/m2/s) for 10 h, and relative humidity of 60%.</li>
	<li>When needed, water the plants with a liquid fertilizer. Refr...

Automated Stomatal Response Measurement to Bacterial Invasion in Arabidopsis

<ol>
	<li>Shimono, M., Higaki, T., Kaku, H., Shibuya, N., Hasezawa, S., Day, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+evaluation+of+stomatal+cytoskeletal+patterns+during+the+activation+of+immune+signaling+in+Arabidopsis+thaliana.">Quantitative evaluation of stomatal cytoskeletal patterns during the activation of immune signaling in Arabidopsis thaliana.</a> PLoS One. 11, e0159291 (2016).</li><li>Bourdais, G., 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+use+of+quantitative+imaging+to+investigate+regulators+of+membrane+trafficking+in+Arabidopsis+stomatal+closure.">The use of quantitative imaging to investigate regulators of membrane trafficking in Arabidopsis stomatal closure.</a> Traffic. 20 (2), 168-180 (2019).</li><li>Higaki, T., Kutsuna, N., Hasezawa, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CARTA-based+semi-automatic+detection+of+stomatal+regions+on+an+Arabidopsis+cotyledon+surface.">CARTA-based semi-automatic detection of stomatal regions on an Arabidopsis cotyledon surface.</a> Plant Morphology. 26 (1), 9-12 (2014).</li><li>Eisele, J. F., F&#228;&#223;ler, F., B&#252;rgel, F., Chaban, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+rapid+and+simple+method+for+microscopy-based+stomata+analyses.">A rapid and simple method for microscopy-based stomata analyses.</a> PLoS One. 11, e0164576 (2016).</li><li>Chitraker, R., Melotto, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessing+stomatal+response+to+live+bacterial+cells+using+whole+leaf+imaging.">Assessing stomatal response to live bacterial cells using whole leaf imaging.</a> Journal of Visualized Experiments. 44, 2185 (2010).</li><li>Sai, N., 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=StomaAI:+an+efficient+and+user-friendly+tool+for+measurement+of+stomatal+pores+and+density+using+deep+computer+vision.">StomaAI: an efficient and user-friendly tool for measurement of stomatal pores and density using deep computer vision.</a> New Phytologist. 238 (2), 904-915 (2023).</li><li>Takagi, M., 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=Image-based+quantification+of+Arabidopsis+thaliana+stomatal+aperture+from+leaf+images.">Image-based quantification of Arabidopsis thaliana stomatal aperture from leaf images.</a> Plant and Cell Physiology. pcad018, (2023).</li><li>Melotto, M., Zhang, L., Oblessuc, P. R., He, S. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stomatal+defense+a+decade+later.">Stomatal defense a decade later.</a> Plant Physiology. 174 (2), 561-571 (2017).</li><li>Melotto, M., Underwood, W., Koczan, J., Nomura, K., He, S. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plant+stomata+function+in+innate+immunity+against+bacterial+invasion.">Plant stomata function in innate immunity against bacterial invasion.</a> Cell. 126 (5), 969-980 (2006).</li><li>Zeng, W., He, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+prominent+role+of+the+flagellin+receptor+FLAGELLIN-SENSING2+in+mediating+stomatal+response+to+Pseudomonas+syringae+pv+tomato+DC3000+in+Arabidopsis.">A prominent role of the flagellin receptor FLAGELLIN-SENSING2 in mediating stomatal response to Pseudomonas syringae pv tomato DC3000 in Arabidopsis.</a> Plant Physiology. 153 (3), 1188-1198 (2010).</li><li>Zheng, X. 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=Coronatine+promotes+Pseudomonas+syringae+virulence+in+plants+by+activating+a+signaling+cascade+that+inhibits+salicylic+acid+accumulation.">Coronatine promotes Pseudomonas syringae virulence in plants by activating a signaling cascade that inhibits salicylic acid accumulation.</a> Cell Host and Microbe. 11 (6), 587-596 (2012).</li><li>Raffeiner, M., 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+Xanthomonas+type-III+effector+XopS+stabilizes+CaWRKY40a+to+regulate+defense+responses+and+stomatal+immunity+in+pepper+(Capsicum+annuum).">The Xanthomonas type-III effector XopS stabilizes CaWRKY40a to regulate defense responses and stomatal immunity in pepper (Capsicum annuum).</a> The Plant Cell. 34 (5), 1684-1708 (2022).</li><li>Munemasa, S., Hauser, F., Park, J., Waadt, R., Brandt, B., Schroeder, J. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanisms+of+abscisic+acid-mediated+control+of+stomatal+aperture.">Mechanisms of abscisic acid-mediated control of stomatal aperture.</a> Current Opinion in Plant Biology. 28, 154-162 (2015).</li><li>F&#246;rster, S., 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=Wounding-induced+stomatal+closure+requires+jasmonate-mediated+activation+of+GORK+K++channels+by+a+Ca2++sensor-kinase+CBL1-CIPK5+complex.">Wounding-induced stomatal closure requires jasmonate-mediated activation of GORK K+ channels by a Ca2+ sensor-kinase CBL1-CIPK5 complex.</a> Developmental Cell. 48 (1), 87-99 (2018).</li><li>Cheng, Y. T., Zhang, L., He, S. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plant-microbe+interactions+facing+environmental+challenge.">Plant-microbe interactions facing environmental challenge.</a> Cell Host and Microbe. 26 (2), 183-192 (2019).</li></ol>

Previous studies used epidermal peels, leaf discs, or detached leaves to investigate stomatal responses to bacterial invasions9,11,12. In contrast, the method proposed in this study leverages the portable stomatal imaging device to directly observe stomata on a leaf attached to the plant after spray inoculation of Pto, mimicking natural conditions of bacterial invasion. In addition, because this method does not involve ...

Stomata are microscopic pores surrounded by a pair of guard cells on the surface of leaves and other aerial parts of plants. Under ever-changing environments, regulation of the stomatal aperture is central for plants to control the carbon dioxide uptake required for photosynthesis at the expense of water loss via transpiration. Thus, quantification of the stomatal aperture has been instrumental to understanding plant environmental adaptation. However, quantifying the stomatal aperture is inherently time-consuming and cumbersome as it requires human labor to spot and measure stomatal pores in a leaf image captured by a microscope. To circumvent these limitations, various methods have been developed to facilitate the quantification of stomatal aperture in Arabidopsis thaliana, a model plant extensively used to study stomatal biology1,2,3,4,5,6. For instance, a porometer can be used to measure transpiration rate as a metric of stomatal conductance. However, this method does not provide direct information on the stomatal number and aperture that determine stomatal conductance. Some studies have used confocal microscopy techniques highlighting stomatal pores using a fluorescent actin marker, a fluorescent dye, or cell wall autofluorescence1,2,3,4,5. While these approaches facilitate the detection of stomata, the cost of both operating a confocal microscopy facility and preparing microscopy samples can be an obstacle to routine application. In a ground-breaking work by Sai et al., a deep neural network model was developed to automatically measure stomatal aperture from bright-field microscopic images of A. thaliana epidermal peels6. Yet, this innovation does not exempt researchers from the task of preparing an epidermal peel for microscopic observation. Recently, this obstacle was overcome by developing a portable imaging device that can observe stomata by pinching a leaf of A. thaliana, together with a deep learning-based image analysis pipeline that automatically measures stomatal aperture from leaf images captured by the device7.
Stomata contribute to plant innate immunity against bacterial pathogens. The key to this immune response is stomatal closure that restricts bacterial entry through the microscopic pore into the leaf interior, where bacterial pathogens proliferate and cause diseases8. Stomatal closure is induced upon recognition of microbe-associated molecular patterns (MAMPs), immunogenic molecules that are often common to a class of microbes, by plasma membrane-localized pattern recognition receptors (PRRs)9. A 22 amino acid epitope of bacterial flagellin known as flg22 is a typical MAMP that induces stomatal closure through its recognition by the PRR FLS210. As a countermeasure, bacterial pathogens such as Pseudomonas syringae pv. tomato DC3000 (Pto) and Xanthomonas campestris pv. vesicatoria have evolved virulence mechanisms to reopen stomata9,11,12. These stomatal responses to bacterial pathogens have been conventionally analyzed in assays in which either leaf epidermal peels, leaf discs, or detached leaves are floated on bacterial suspension, and then stomata are observed under a microscope followed by manual measurement of stomatal aperture. However, these assays are cumbersome and may not reflect stomatal responses to natural bacterial invasion that occur in a leaf attached to the plant.
Here, a simple method is presented to investigate stomatal closure and reopening during Pto invasion under the condition that closely mimics the natural plant-bacteria interaction. This method leverages the portable imaging device for direct observation of A. thaliana stomata on a leaf attached to the plant inoculated with Pto, together with the image analysis pipeline for automated measurement of stomatal aperture.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Agar</td>
			<td>Nakarai tesque</td>
			<td>01028-85</td>
			<td></td>
		</tr>
		<tr>
			<td>Airbrush kits</td>
			<td>ANEST IWATA</td>
			<td>MX2900</td>
			<td>Accessory kits for SPRINT JET</td>
		</tr>
		<tr>
			<td>Biotron</td>
			<td>Nippon Medical &#38; Chemical Instruments</td>
			<td>LPH-411S</td>
			<td>Plant Growth Chamber with white fluorescent light</td>
		</tr>
		<tr>
			<td>Glycerol</td>
			<td>Wako</td>
			<td>072-00626</td>
			<td></td>
		</tr>
		<tr>
			<td>Half tray</td>
			<td>Sakata</td>
			<td>72000113</td>
			<td>A set of tray and lid</td>
		</tr>
		<tr>
			<td>Hyponex</td>
			<td>Hyponex</td>
			<td>No catalogue number available</td>
			<td>Dilute the solution of Hyponex at a ratio of 1:2000 in deionized water for watering plants</td>
		</tr>
		<tr>
			<td>Image J</td>
			<td>Natinal Institute of Health</td>
			<td>Download at https://imagej.nih.gov/ij/download.html</td>
			<td>Used for manual measurement of stomatal aperture</td>
		</tr>
		<tr>
			<td>K2HPO4</td>
			<td>Wako</td>
			<td>164-04295</td>
			<td></td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Wako</td>
			<td>163-03545</td>
			<td></td>
		</tr>
		<tr>
			<td>KOH</td>
			<td>Wako</td>
			<td>168-21815</td>
			<td>For MES-KOH</td>
		</tr>
		<tr>
			<td>MES</td>
			<td>Wako</td>
			<td>343-01621</td>
			<td>For MES-KOH</td>
		</tr>
		<tr>
			<td>Portable stomatal imaging device</td>
			<td>Phytometrics</td>
			<td>Order at https://www.phytometrics.jp/</td>
			<td>Takagi et al.(2023) doi: 10.1093/pcp/pcad018.</td>
		</tr>
		<tr>
			<td>Rifampicin</td>
			<td>Wako</td>
			<td>185-01003</td>
			<td>Dissolve in DMSO</td>
		</tr>
		<tr>
			<td>Silwet-L77</td>
			<td>Bio medical science</td>
			<td>BMS-SL7755</td>
			<td>silicone surfactant used in spray inoculation</td>
		</tr>
		<tr>
			<td>SPRINT JET</td>
			<td>ANEST IWATA</td>
			<td>IS-800</td>
			<td>Airbrush used for spray inoculation</td>
		</tr>
		<tr>
			<td>SuperMix A</td>
			<td>Sakata seed</td>
			<td>72000083</td>
			<td>Mix with Vermiculite G20 in equal proportions for preparing soil</td>
		</tr>
		<tr>
			<td>Tryptone</td>
			<td>Nakarai tesque</td>
			<td>35640-95</td>
			<td></td>
		</tr>
		<tr>
			<td>Vermiculite G20</td>
			<td>Nittai</td>
			<td>No catalogue number available</td>
			<td>Mix with Super Mix A in equal proportions for preparing soil</td>
		</tr>
		<tr>
			<td>White fluorescent light</td>
			<td>NEC</td>
			<td>FHF32EX-N-HX-S</td>
			<td>Used for Biotron</td>
		</tr>
	</tbody>
</table>

direct observation and automated measurement of stomatal responses to pseudomonas syringae pv. tomato dc3000 in arabidopsis thaliana

Stomata are microscopic pores found in the plant leaf epidermis. Regulation of stomatal aperture is pivotal not only for balancing carbon dioxide uptake for photosynthesis and transpirational water loss but also for restricting bacterial invasion. While plants close stomata upon recognition of microbes, pathogenic bacteria, such as Pseudomonas syringae pv. tomato DC3000 (Pto), reopen the closed stomata to gain access into the leaf interior. In conventional assays for assessing stomatal responses to bacterial invasion, leaf epidermal peels, leaf discs, or detached leaves are floated on bacterial suspension, and then stomata are observed under a microscope followed by manual measurement of stomatal aperture. However, these assays are cumbersome and may not reflect stomatal responses to natural bacterial invasion in a leaf attached to the plant. Recently, a portable imaging device was developed that can observe stomata by pinching a leaf without detaching it from the plant, together with a deep learning-based image analysis pipeline designed to automatically measure stomatal aperture from leaf images captured by the device. Here, building on these technical advances, a new method to assess stomatal responses to bacterial invasion in Arabidopsis thaliana is introduced. This method consists of three simple steps: spray inoculation of Pto mimicking natural infection processes, direct observation of stomata on a leaf of the Pto-inoculated plant using the portable imaging device, and automated measurement of stomatal aperture by the image analysis pipeline. This method was successfully used to demonstrate stomatal closure and reopening during Pto invasion under conditions that closely mimic the natural plant-bacteria interaction.

Author Spotlight: Advancing Stomatal Research with Automated Aperture Measurement

Direct Observation and Automated Measurement of Stomatal Responses to Pseudomonas syringae pv. tomato DC3000 in Arabidopsis thaliana

Plantal stomata play central roles in adaptation to stress conditions, so we need to measure stomata aperture to understand how plants respond to biotic and abiotic stresses. However, stomata aperture measurement is time-consuming and cumbersome. To measure stomata aperture, we peel the epidermis and observe stomata under a microscope.Then we manually measure stomata aperture, which takes a long time even for very experienced researchers. We challenged these barriers and developed a tool and a technique that can automatically measure stomata aperture in intact Arabidopsis leaves. So we strongly believe that stomata measuring device and deep-learning algorithm that we developed will facilitate functional analysis of stomata responses to various biotic and abiotic stresses because these technical advances significantly reduce time and human labor required for stomata aperture measurement.

Following spray inoculation of Pto, stomata on leaves attached to the inoculated plants were directly observed by the portable stomatal imaging device. Using manual and automated measurements, the same leaf images were used to calculate stomatal aperture by taking ratios of width to length of approximately 60 stomata. Manual and automated measurements consistently indicated a decrease in the stomatal aperture in Pto-inoculated plants compared with mock-inoculated plants at 1 hour post inoculation (hpi) ...

Watch this Scientific Journal Video about Author Spotlight: Advancing Stomatal Research with Automated Aperture Measurement at JoVE.com

Here, we present a simple method for direct observation and automated measurement of stomatal responses to bacterial invasion in Arabidopsis thaliana. This method leverages a portable stomatal imaging device, together with an image analysis pipeline designed for leaf images captured by the device.

Stomata are microscopic pores found in the plant leaf epidermis. Regulation of stomatal aperture is pivotal not only for balancing carbon dioxide uptake ...