WRKY70 and WRKY54 co-operate as negative regulators of stomatal closure

Fig. 8 Fast stomatal response to abscisic acid (ABA) and polyethylene glycol (PEG). (a) Comparison of stomatal aperture in response to ABA. Scale bar = 10 lm. (b) Ratio of stomatal aperture length over width. Data were calculated from 100 stomata from leaves of three different plants of Arabidopsis. Values are mean SD. The experiments were performed three times with similar results (*, P < 0.01, one-way ANOVA test). (c) Comparison of stomatal aperture in response to PEG treatment. Scale bar = 10 lm. (d) Ratio of stomatal aperture length over width. Data were calculated from 100 stomata of leaves of three different plants of Arabidopsis. Values are mean SD. The experiments were performed three times with similar results (*, P < 0.01, one-way ANOVA test).

 

Defense-related transcription factors WRKY70 and WRKY54 modulate osmotic stress tolerance by regulating stomatal aperture in Arabidopsis.

by Li J., Besseau S., Törönen P., Sipari N., Kollist H., Holm L., Palva E. T. (2013)

Li Jing, Besseau Sebastien, Törönen Petri, Sipari Nina Hannele, Kollist Hannes, Holm Liisa, Palva E. Tapio,

Viikki Biocenter, Division of Genetics, Department of Biosciences, University of Helsinki, FI-00014, Helsinki, Finland.

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in New Phytol 200: 457–472 – doi: 10.1111/nph.12378. Epub 2013 Jul 1. –

CrossRef PubMed PubMedCentral Google Scholar – 

https://www.ncbi.nlm.nih.gov/pubmed/23815736

Abstract

WRKY transcription factors (TFs) have been mainly associated with plant defense, but recent studies have suggested additional roles in the regulation of other physiological processes. Here, we explored the possible contribution of two related group III WRKY TFs, WRKY70 and WRKY54, to osmotic stress tolerance.

These TFs are positive regulators of plant defense, and co-operate as negative regulators of salicylic acid (SA) biosynthesis and senescence. We employed single and double mutants of wrky54 and wrky70, as well as a WRKY70 overexpressor line, to explore the role of these TFs in osmotic stress (polyethylene glycol) responses. Their effect on gene expression was characterized by microarrays and verified by quantitative PCR.

Stomatal phenotypes were assessed by water retention and stomatal conductance measurements. The wrky54wrky70 double mutants exhibited clearly enhanced tolerance to osmotic stress. However, gene expression analysis showed reduced induction of osmotic stress-responsive genes in addition to reduced accumulation of the osmoprotectant proline.

By contrast, the enhanced tolerance was correlated with improved water retention and enhanced stomatal closure.

These findings demonstrate that WRKY70 and WRKY54 co-operate as negative regulators of stomatal closure and, consequently, osmotic stress tolerance in Arabidopsis, suggesting that they have an important role, not only in plant defense, but also in abiotic stress signaling.

SLAC1-type anion channels and flagellin-induced stomatal closure

Fig. 1 Nanoinfusion of flg22 and ABA triggers rapid stomatal closure in intact Arabidopsis leaves. (a) Illustration of the nanoinfusion technique used to induce flg22- and ABA-dependent stomatal closure. A microcapillary was moved into the substomatal cavity of an open stoma and used to infuse solutions into the intercellular space. Movement of neighboring stomata was monitored on an upright microscope. (b) Images of a stoma in the abaxial epidermis of an Arabidopsis leaf stimulated by nanoinfusion of 20 nM flg22. Images were obtained just before (left panel), directly after (middle panel), and 35 min after stimulation with flg22 (right panel). Note that the leaf becomes transparent because of solution infused into the intercellular space. (c) Time-dependent changes in average stomatal aperture before and after stimulation with control solution (closed circles, n = 8), 10 lM ABA (open circles, n = 13), or 20 nM flg22 (open triangles, n = 13); the arrow indicates the time point of nanoinfusion. Data are presented as average values of 8 to 13 stomata of at least three independent experiments, and error bars represent SE.

Guard cell SLAC1-type anion channels mediate flagellin-induced stomatal closure

by Deger A. G., Scherzer S., Nuhkat M., Kedzierska J., Kollist H., Brosche M., Unyayar S., Boudsocq M., Hedrich R., Roelfsema M. R. G. (2015)

Aysin Guzel Deger

Mersin University – Faculty of Science and Letters, Department of Biology, Mersin, Turquie.

University of Würzburg – Molecular Plant Physiology and Biophysics, Julius-von-Sachs Institute for Biosciences, Biocenter, Würzburg, Allemagne.

Soenke Scherzer

University of Würzburg – Molecular Plant Physiology and Biophysics, Julius-von-Sachs Institute for Biosciences, Biocenter, Würzburg, Allemagne.

Maris Nuhkat

University of Tartu – Institute of Technology, Tartu, Estonie.

Justyna Kedzierska

University of Würzburg – Molecular Plant Physiology and Biophysics, Julius-von-Sachs Institute for Biosciences, Biocenter, Würzburg, Allemagne.

Hannes Kollist

University of Tartu – Institute of Technology, Tartu, Estonie.

Mikael Brosche

University of Helsinki – Division of Plant Biology, Department of Biosciences, Helsinki, Finlande.

University of Tartu – Institute of Technology, Tartu, Estonie.

Serpil Unyayar

Mersin University – Faculty of Science and Letters, Department of Biology, Mersin, Turquie.

Marie Boudsocq

INRA – U. Evry – U. Paris 11 (U. Paris Sud) – CNRS – U. Paris 7, UMR 1403 IPS2 Institut des Sciences des Plantes de Paris Saclay. Centre de recherche de Versailles-Grignon, Evry, France.

CNRS, Centre National de la Recherche Scientifique – UMR 9213 Institute of Plant Sciences Paris-Saclay, Université Paris Sud-Université Evry Val d’Essonne-Université Paris Diderot, Orsay, France.

Rainer Hedrich

University of Würzburg – Molecular Plant Physiology and Biophysics, Julius-von-Sachs Institute for Biosciences, Biocenter, Würzburg, Allemagne.

M. Rob G. Roelfsema

roelfsema@botanik.uni-wuerzburg.de

University of Würzburg – Molecular Plant Physiology and Biophysics, Julius-von-Sachs Institute for Biosciences, Biocenter, Würzburg, Allemagne.

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in New Phytologist 208(1): 162-173 – DOI: 10.1111/nph.13435 –

https://helda.helsinki.fi/handle/10138/209596

http://onlinelibrary.wiley.com/store/10.1111/nph.13435/asset/nph13435.pdf;jsessionid=49EF146069C152693831AB7AE6B4AE9C.f03t03?v=1&t=j9qxsuc6&s=67dc0fb441bbdd3e6c3027ff6d5f4800c1985819

Abstract

During infection plants recognize microbe-associated molecular patterns (MAMPs), and this leads to stomatal closure.

This study analyzes the molecular mechanisms underlying this MAMP response and its interrelation with ABA signaling. Stomata in intact Arabidopsis thaliana plants were stimulated with the bacterial MAMP flg22, or the stress hormone ABA, by using the noninvasive nanoinfusion technique. Intracellular double-barreled microelectrodes were applied to measure the activity of plasma membrane ion channels.

Flg22 induced rapid stomatal closure and stimulated the SLAC1 and SLAH3 anion channels in guard cells. Loss of both channels resulted in cells that lacked flg22-induced anion channel activity and stomata that did not close in response to flg22 or ABA.

Rapid flg22-dependent stomatal closure was impaired in plants that were flagellin receptor (FLS2)-deficient, as well as in the ost1-2 (Open Stomata 1) mutant, which lacks a key ABA-signaling protein kinase.

By contrast, stomata of the ABA protein phosphatase mutant abi1-1 (ABscisic acid Insensitive 1) remained flg22-responsive.

These data suggest that the initial steps in flg22 and ABA signaling are different, but that the pathways merge at the level of OST1 and lead to activation of SLAC1 and SLAH3 anion channels.