Guard cell <scp>SLAC</scp>1‐type anion channels mediate flagellin‐induced stomatal closure

<jats:title>Summary</jats:title><jats:p> <jats:list list-type="bullet"> <jats:list-item><jats:p>During infection plants recognize microbe‐associated molecular patterns (<jats:styled-content style="fixed-case">MAMP</jats:styled-content>s), and this leads to stomatal closure. This study analyzes the molecular mechanisms underlying this <jats:styled-content style="fixed-case">MAMP</jats:styled-content> response and its interrelation with <jats:styled-content style="fixed-case">ABA</jats:styled-content> signaling.</jats:p></jats:list-item> <jats:list-item><jats:p>Stomata in intact <jats:italic>Arabidopsis thaliana</jats:italic> plants were stimulated with the bacterial <jats:styled-content style="fixed-case">MAMP</jats:styled-content> flg22, or the stress hormone <jats:styled-content style="fixed-case">ABA</jats:styled-content>, by using the noninvasive nanoinfusion technique. Intracellular double‐barreled microelectrodes were applied to measure the activity of plasma membrane ion channels.</jats:p></jats:list-item> <jats:list-item><jats:p>Flg22 induced rapid stomatal closure and stimulated the <jats:styled-content style="fixed-case">SLAC</jats:styled-content>1 and <jats:styled-content style="fixed-case">SLAH</jats:styled-content>3 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 <jats:styled-content style="fixed-case">ABA</jats:styled-content>. Rapid flg22‐dependent stomatal closure was impaired in plants that were flagellin receptor (<jats:styled-content style="fixed-case">FLS</jats:styled-content>2)‐deficient, as well as in the <jats:italic>ost1‐2</jats:italic> (<jats:italic>Open Stomata 1</jats:italic>) mutant, which lacks a key <jats:styled-content style="fixed-case">ABA</jats:styled-content>‐signaling protein kinase. By contrast, stomata of the <jats:styled-content style="fixed-case">ABA</jats:styled-content> protein phosphatase mutant <jats:italic>abi1‐1</jats:italic> (<jats:italic><jats:styled-content style="fixed-case">AB</jats:styled-content>scisic acid Insensitive 1</jats:italic>) remained flg22‐responsive.</jats:p></jats:list-item> <jats:list-item><jats:p>These data suggest that the initial steps in flg22 and <jats:styled-content style="fixed-case">ABA</jats:styled-content> signaling are different, but that the pathways merge at the level of <jats:styled-content style="fixed-case">OST</jats:styled-content>1 and lead to activation of <jats:styled-content style="fixed-case">SLAC</jats:styled-content>1 and <jats:styled-content style="fixed-case">SLAH</jats:styled-content>3 anion channels.</jats:p></jats:list-item> </jats:list> </jats:p>