title: Requirement for pectin methyl esterase and preference for fragmented over native pectins for wall-associated kinase-activated, EDS1/PAD4-dependent stress response in Arabidopsis.
abstract: The wall-associated kinases (WAKs) have a cytoplasmic protein kinase domain that spans the plasma membrane and binds pectin in the extracellular matrix of plants. WAKs are required for cell expansion during Arabidopsis seedling development but are also an integral part of the response to pathogens and stress that present oligogalacturonides (OGs), which subsequently bind to WAKs and activate a MPK6 (mitogen-activated protein kinase)-dependent pathway. It was unclear how WAKs distinguish native pectin polymers and OGs to activate one or the other of these two pathways. A dominant allele of WAK2 constitutively activates the stress response, and we show here that the effect is dependent upon EDS1 and PAD4, transcriptional activators involved in the pathogen response. Moreover, the WAK2 dominant allele is suppressed by a null allele of a pectin methyl esterase (PME3) whose activity normally leads to cross-linking of pectins in the cell wall. Although OGs activate a transcriptional response in wild type, the response is enhanced in a pme3/pme3 null, consistent with a competition by OG and native polymers for activation of WAKs. This provides a plausible mechanism for WAKs to distinguish an expansion from a stress pathway.
authors.affiliation: From the Department of Biology, Bowdoin College, Brunswick, Maine 04011 bkohorn@bowdoin.edu.
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Kohorn
authors.affiliation: From the Department of Biology, Bowdoin College, Brunswick, Maine 04011.
authors.forename: Susan L
authors.initials: SL
authors.lastname: Kohorn
authors.affiliation: From the Department of Biology, Bowdoin College, Brunswick, Maine 04011.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Saba
authors.affiliation: From the Department of Biology, Bowdoin College, Brunswick, Maine 04011.
authors.forename: Victoriano Meco
authors.initials: VM
authors.lastname: Martinez
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002265:Carboxylic Ester Hydrolases / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004951:Esterification; D010368:Pectins / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D013312:Stress, Physiological; D013379:Substrate Specificity; D014158:Transcription, Genetic
chemical_list: D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; C118837:EDS1 protein, Arabidopsis; D010368:Pectins; D011494:Protein Kinases; D002265:Carboxylic Ester Hydrolases; C400766:PAD4 protein, Arabidopsis; C568893:pectin methylesterase 3, Arabidopsis
keywords: Arabidopsis; Cell Wall; Plant Defense; Receptor; Receptors; Signaling