Multiple functional self-association interfaces in plant TIR domains

Significance Toll/interleukin-1 receptor/resistance protein (TIR) domains are present in plant and animal innate immunity receptors and appear to play a scaffold function in defense signaling. In both systems, self-association of TIR domains is crucial for their function. In plants, the TIR domain is associated with intracellular immunity receptors, known as nucleotide-binding oligomerization domain-like receptors (NLRs). Previous studies from several plant NLRs have identified two distinct interfaces that are required for TIR:TIR dimerization in different NLRs. We show that the two interfaces previously identified are both important for self-association and defense signaling of multiple TIR–NLR proteins. Collectively, this work suggests that there is a common mechanism of TIR domain self-association in signaling across the TIR–NLR class of receptor proteins.