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).
Project description:The encoding genes of plant intracellular nucleotide-binding site (NBS) and leucine-rich repeat (LRR) domain receptors (NLRs) often exist in the form of a gene cluster. Several recent studies demonstrated that the truncated Toll/interleukin-1 receptor-NBS (TIR-NBS) proteins play important roles in immunity. In this study, we identified a large TN gene cluster on Arabidopsis ecotype Col-0 chromosome 1, which included nine TN genes, TN4 to TN12. Interestingly, this cluster also contained two typical TIR-NBS-LRR genes: At1g72840 and At1g72860 (hereinafter referred to as TNL40 and TNL60, respectively), which formed head-to-head genomic arrangement with TN4 to TN12. However, the functions of these TN and TNL genes in this cluster are still unknown. Here, we showed that the TIR domains of both TNL40 and TNL60 associated with TN10 specifically. Furthermore, both TNL40TIR and TNL60TIR induced cell death in Nicotiana tabacum leaves. Subcellular localization showed that TNL40 mainly localized in the cytoplasm, whereas TNL60 and TN10 localized in both the cytoplasm and nucleus. Additionally, the expression of TNL40, TNL60, and TN10 were co-regulated after inoculated with bacterial pathogens. Taken together, our study indicates that the truncated TIR-NBS protein TN10 associates with two clustered TNL immune receptors, and may work together in plant disease resistance.
Project description:Intracellular NLR receptors with a central nucleotide-binding domain allow plants to detect specific pathogen-secreted proteins and initiate immune signaling. A family of conserved Enhanced disease susceptibility 1 proteins with a lipase-like and the EP domain transduces the signal from activated NLRs downstream. This family includes EDS1, PAD4 and SAG101 that form mutually exclusive heterodimers EDS1-PAD4 and EDS1-SAG101. Despite sequence similarities, PAD4 and SAG101 control different aspects of NLR immune signaling. More specifically, PAD4 and SAG101 regulate resistance and cell death outputs of the NLR receptor pair RRS1-RPS4, respectively. Also, PAD4 and SAG101 genetically cooperate with distinct downstream signaling NLRs - ADR1 and NRG1. The main aim of this IP-LC/MS project is to assess whether PAD4 and SAG101 form complexes with ADR1 and NRG1 and to gain insight into mechanisms of the genetically established functional links between EDS1 family proteins and downstream signaling NLRs.
