Albrecht, CatherineBoutrot, FreddySegonzac, CecileSchwessinger, BenjaminGimenez-Ibanez, SelenaChinchilla, DelphineRathjen, Johnde Vries, Sacco CZipfel, Cyril2015-12-100027-8424http://hdl.handle.net/1885/50789Plants 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.Author/s retain copyrightKeywords: brassinosteroid; brassinosteroid insensitive 1; BRI1 associated Kinase 1; chitin; flagellin; flagellin sensing 2; mitogen activated protein kinase 3; mitogen activated protein kinase 6; protein kinase; unclassified drug; Arabidopsis; article; controlled s Brassinosteroid insensitive 1; BRI1-associated kinase 1; Cross-talk; Flagellin sensing 2201110.1073/pnas.11099211082016-02-24