title: Brassinosteroids inhibit pathogen-associated molecular pattern-triggered immune signaling independent of the receptor kinase BAK1.
abstract: Plants and animals use innate immunity as a first defense against pathogens, a costly yet necessary tradeoff between growth and immunity. In Arabidopsis, the regulatory leucine-rich repeat receptor-like kinase (LRR-RLK) BAK1 combines with the LRR-RLKs FLS2 and EFR in pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and the LRR-RLK BRI1 in brassinosteroid (BR)-mediated growth. Therefore, a potential tradeoff between these pathways mediated by BAK1 is often postulated. Here, we show a unidirectional inhibition of FLS2-mediated immune signaling by BR perception. Unexpectedly, this effect occurred downstream or independently of complex formation with BAK1 and associated downstream phosphorylation. Thus, BAK1 is not rate-limiting in these pathways. BRs also inhibited signaling triggered by the BAK1-independent recognition of the fungal PAMP chitin. Our results suggest a general mechanism operative in plants in which BR-mediated growth directly antagonizes innate immune signaling.
authors.affiliation: Laboratory of Biochemistry,  Wageningen University, 6703 HA Wageningen,  The Netherlands.
authors.forename: Catherine
authors.initials: C
authors.lastname: Albrecht
authors.forename: Freddy
authors.initials: F
authors.lastname: Boutrot
authors.forename: Cécile
authors.initials: C
authors.lastname: Segonzac
authors.forename: Benjamin
authors.initials: B
authors.lastname: Schwessinger
authors.forename: Selena
authors.initials: S
authors.lastname: Gimenez-Ibanez
authors.forename: Delphine
authors.initials: D
authors.lastname: Chinchilla
authors.forename: John P
authors.initials: JP
authors.lastname: Rathjen
authors.forename: Sacco C
authors.initials: SC
authors.lastname: de Vries
authors.forename: Cyril
authors.initials: C
authors.lastname: Zipfel
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology / Q000276:immunology* / Q000382:microbiology*; D029681:Arabidopsis Proteins / Q000378:metabolism; D060406:Brassinosteroids / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D005408:Flagellin / Q000494:pharmacology; D057865:Plant Immunity / Q000187:drug effects* / Q000276:immunology; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011549:Pseudomonas / Q000187:drug effects / Q000378:metabolism*; D051192:Receptors, Pattern Recognition / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects* / Q000276:immunology; D013260:Steroids, Heterocyclic / Q000494:pharmacology
chemical_list: D029681:Arabidopsis Proteins; D060406:Brassinosteroids; D051192:Receptors, Pattern Recognition; D013260:Steroids, Heterocyclic; D005408:Flagellin; D011494:Protein Kinases; C463660:BAK1 protein, Arabidopsis; C411853:FLS2 protein, Arabidopsis; C108270:BRI1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases; C023623:brassinolide
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