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)
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in New Phytologist 208(1): 162-173 – DOI: 10.1111/nph.13435 –
https://helda.helsinki.fi/handle/10138/209596
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.
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