Project description:Toll/interleukin-1 receptor (TIR) domains across different life kingdoms possess NADase activities and produce distinct small molecules including phosphoribosyl adenosine monophosphate/diphosphate (pRib-AMP/ADP) and two cyclic ADPR (cADPR) isomers 2’cADPR and 3’cADPR. Plant intracellular nucleotide-binding leucine-rich repeat (NLR) receptors with an N-terminal TIR domain sense pathogen effectors to initiate immune signaling and rely on downstream helper NLRs to execute immune function. Lipase-like proteins EDS1 and PAD4 transduce immune signals from sensor TIR-NLRs to a helper NLR called ADR1. We report the structure and function of Arabidopsis EDS1-PAD4-ADR1 (EPA) heterotrimer in complex with pRib-AMP/ADP activated by plant or bacterial TIR signaling. Bacterial TIRs that produce 2’cADPR, but not 3’cADPR, induce EPA complex formation and activate EPA signaling using pRib-AMP as the signaling molecule. 2’cADPR is hydrolyzed into pRib-AMP in vivo. 2’cADPR, but not 3’cADPR, induces EPA-dependent defense genes expression. Our findings shed light on the activation mechanisms of ADR1 by EDS1-PAD4 involving two structurally-related molecules with 2’cADPR likely being the storage form of the unstable signaling molecule pRib-AMP, as well as cross-talks between plant and bacterial TIR immune signaling.
Project description:Plants deploy cell surface and intracellular leucine rich-repeat domain (LRR) immune receptors to detect pathogens. LRR receptor kinases (LRR-RKs) and LRR receptor proteins (LRR-RPs) recognise microbe-derived molecules to elicit pattern-triggered immunity (PTI), whereas nucleotide-binding LRR (NLR) proteins detect microbial effectors inside cells to confer effector-triggered immunity (ETI). Although PTI and ETI are initiated in different host cell compartments, they rely on the transcriptional activation of similar sets of genes, suggesting pathway convergence upstream of nuclear events. We report that PTI triggered by Arabidopsis LRR-RP (RLP23) requires signalling-competent dimers of the lipase-like proteins EDS1 and PAD4, and ADR1-family helper NLRs, which are all components of ETI. The cell surface LRR-RK SOBIR1 links RLP23 with EDS1, PAD4 and ADR1 proteins, suggesting formation of constitutive supramolecular complexes containing PTI receptors and transducers at the inner side of the plasma membrane.
Project description:Investigate the function of RNLs in transcriptional reprogramming during Pf0-1-induced PTI and ETI, using time-resolved transcriptomics. To do so we subjected Col-0, adr1 triple, nrg1.1 nrg1.2 and helperless mutants to infections with Pf0-EV (RNL-(in)dependent PTI), Pf0-AvrRps4 (fully RNL-dependent ETI + PTI), Pf0-AvrRpt2 (partial RNL-dependent ETI + PTI) or Pf0-AvrRpm1 (RNL-independent ETI + PTI).
