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

Aysin Guzel Deger,Maris Nuhkat,Rainer Hedrich,Mikael Brosché,Marie Boudsocq,Serpil Unyayar,Hannes Kollist,M Rob G Roelfsema,Sönke Scherzer,Justyna Kedzierska

doi:10.1111/nph.13435

Abstract

Summary 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.

Highlights

Pathogenic bacteria take advantage of stomatal pores in the leaf surface to enter their host plants
Based on the results with several signaling mutants, we found that microbe-associated molecular patterns (MAMPs)- and ABA-signaling pathways meet at the level of the protein kinase OST1
The mutants ost1-2 and abi1-1 (ABA Insensitive 1-1) were in the Landsberg erecta (Ler) background, whereas cpk3/5/6/11, rbohD/F (Respiratory Burst Oxidase Homologs-D/F), slac1-3 and slah3-1 were in Columbia 0 (Col-0) and FLS2 was expressed in Wassilewskija (Ws-0) (Zipfel et al, 2004)

Summary

Introduction

Pathogenic bacteria take advantage of stomatal pores in the leaf surface to enter their host plants. Plant cells recognize microbe-associated molecular patterns (MAMPs), such as flagellin or chitosan, and counteract the microbial invasion by stomatal closure (Melotto et al, 2006, 2008; Schulze-Lefert & Robatzek, 2006; Boller & Felix, 2009). The drought hormone ABA causes stomatal closure, by activating the S-type anion channels, slow anion channel 1 (SLAC1) and SLAC1 homolog 3 (SLAH3) (Roelfsema et al, 2012). Because of these similarities in responses to ABA and MAMPs, we compared stomatal responses induced by both stimuli and studied the signaling pathways that target the SLAC1 and SLAH3 anion channels.

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Results

Discussion

Conclusion