title: The plant innate immunity response in stomatal guard cells invokes G-protein-dependent ion channel regulation.
abstract: Stomata in the epidermis of terrestrial plants are important for CO2 absorption and transpirational water loss, and are also potential points of entry for pathogens. Stomatal opening and closure are controlled by distinct mechanisms. Arabidopsis stomata have been shown to close in response to bacteria and pathogen-associated molecular patterns (PAMPs) as part of PAMP-triggered immunity (PTI). Here we show that flg22, a PAMP derived from bacterial flagellin, also inhibits light-induced stomatal opening. Consistent with our observations on stomatal opening, flg22 inhibits the inward K+ channels (K+ (in) currents) of guard cells that mediate K+ uptake during stomatal opening. Similar to previously documented K+ current changes triggered by exogenous elevation of H(2)O(2) and nitric oxide (NO), with prolonged duration of flg22 exposure the outward K+ channels (K+ (out) currents) of guard cells are also inhibited. In null mutants of the flg22 receptor, FLS2, flg22 regulation of stomatal opening, K+ (in) currents, and K+ (out) currents is eliminated. flg22 also fails to elicit these responses in null mutants of the sole canonical G-protein alpha subunit, GPA1. The bacterial toxin, coronatine, produced by several pathogenic strains of Pseudomonas syringae, reverses the inhibitory effects of flg22 on both K+ (in) currents and stomatal opening, indicating interplay between plant and pathogen in the regulation of plant ion channels. Thus, the PAMP-triggered stomatal response involves K+ channel regulation, and this regulation is dependent on signaling via cognate PAMP receptors and a heterotrimeric G-protein. These new findings provide insights into the largely elusive signaling process underlying PTI-associated guard cell responses.
authors.affiliation: Biology Department, Penn State University, University Park, PA 16802-5301, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.forename: Sheng Yang
authors.initials: SY
authors.lastname: He
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Assmann
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D017360:Arabidopsis / Q000276:immunology / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism; D005408:Flagellin / Q000378:metabolism*; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels / Q000276:immunology / Q000378:metabolism*; D044385:GTP-Binding Protein alpha Subunits / Q000378:metabolism; D007192:Indenes / Q000378:metabolism; D015640:Ion Channel Gating; D008027:Light; D054046:Plant Stomata / Q000276:immunology / Q000378:metabolism* / Q000528:radiation effects; D011494:Protein Kinases / Q000378:metabolism
chemical_list: D000596:Amino Acids; D029681:Arabidopsis Proteins; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; C429765:GPA1 protein, Arabidopsis; D044385:GTP-Binding Protein alpha Subunits; D007192:Indenes; D005408:Flagellin; C058487:coronatine; D011494:Protein Kinases; C411853:FLS2 protein, Arabidopsis