Shouguang Huang,1,† Meiqi Ding,1,† M. Rob G. Roelfsema,1,* Ingo Dreyer,2 Sönke Scherzer,1 Khaled A. S. Al-Rasheid,3 Shiqiang Gao,1,4 Georg Nagel,1,4 Rainer Hedrich,1,* and Kai R. Konrad1,*


1Molecular Plant Physiology and Biophysics, Julius-von-Sachs Institute for Biosciences, Biocenter, Würzburg University, Julius-von-Sachs-Platz 2, D-97082 Würzburg, Germany.
2Center of Bioinformatics, Simulation and Modeling (CBSM), Faculty of Engineering, Universidad de Talca, 2 Norte 685, 3460000 Talca, Chile.
3Zoology Department, College of Science, King Saud University, 11451 Riyadh, Saudi Arabia.
4Institute of Physiology, Würzburg University, Röntgenring 9, 97070 Würzburg, Germany.
*Corresponding author. Email: [email protected] (R.H.); [email protected] (M.R.G.R); [email protected] (K.R.K)
†These authors contributed equally to this work.


Cell Biology, Optogenetics


Guard cells control the aperture of plant stomata, which are crucial for global fluxes of CO2 and water. In turn, guard cell anion channels are seen as key players for stomatal closure, but is activation of these channels sufficient to limit plant water loss? To answer this open question, we used an optogenetic approach based on the light-gated anion channelrhodopsin 1 (GtACR1). In tobacco guard cells that express GtACR1, blue- and green-light pulses elicit Cl− and NO3− currents of −1 to −2 nA. The anion currents depolarize the plasma membrane by 60 to 80 mV, which causes opening of voltage-gated K+ channels and the extrusion of K+. As a result, continuous stimulation with green light leads to loss of guard cell turgor and closure of stomata at conditions that provoke stomatal opening in wild type. GtACR1 optogenetics thus provides unequivocal evidence that opening of anion channels is sufficient to close stomata.



The light pulses were provided by an LED illumination system (pE-4000, CoolLED, UK), in which most of the visible spectrum is covered by 16 LEDs. 

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The pE-4000 Universal Illumination System offers 16 selectable wavelengths from 365 - 770 nm, making it a highly flexible illuminator covering a wide variety of fluorophores

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