Brassinosteroids inhibit pathogen-associated molecular pattern-triggered immune signaling independent of the receptor kinase BAK1 

 -  PNAS, 109(1), p.303-308, 2012 .
<br/><br/> 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 mmunity (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 ndependently 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 
<br/><br/><label>Subjects--Topical Terms: </label><br/>FLAGELLIN SENSING<br/>BRASSINOSTEROID INSENSITIVE<br/>BRI<br/>ASSOCIATED KINASE<br/>CROSS-TALK