Project description:During pattern-triggered immunity (PTI), the first line of active defense against infection in plants, the translatome undergoes rapid reprogamming. To understand how defense proteins are selectively translated, we conducted a genetic screen for regulators of PTI using a translational reporter. We identified a mutant of RNA helicase 12 (RH12) showing compromised reporter translation and pathogen resistance. RH12 is a homolog of yeast DEAD-box Helicase Homolog 1, which targets mRNAs with low codon optimality for decay. Therefore, we sequenced the Arabidopsis tRNAome to determine codon optimality during PTI. We discovered a PTI-associated reduction in overall codon optimality of the transcriptome, and found that the decay of transcripts with reduced optimality is mediated by interaction with RH12. Our results demonstrate the first example of codon optimality-associated decay as part of an adaptive response in which the dynamics of both the tRNAome and the transcriptome facilitate rapid changes in translational output during PTI.
Project description:Plants have evolved a two-layered immune system that mainly includes pattern-triggered immunity (PTI) and effector-triggered immunity (ETI) against pathogen attack. PTI and ETI signaling are functionally linked, but also distinct due to specific perceived ligands and activation modes. Unraveling how PTI and ETI coordinate the immune responses against pathogens is crucial for understanding the regulatory mechanisms in plant immunity. To better understand the protein profiling and phosphorylation events during PTI and ETI, we employed integrated whole proteome and phosphoproteome analyses in the tomato-Pst pathosystem with different Pst DC3000 mutants that allow dissection of different layers of immune responses. A total of 225 proteins and 79 phosphopeptides were differentially regulated in tomato leaves during immune responses. Our proteomics results indicate that some overlapping immune responses are triggered by both PTI and ETI-inducing treatment, and ETI response is more robust than PTI response for most proteins. The change patterns of protein abundance and phosphorylation revealed some key regulators involved in Ca2+ signaling, mitogen-activated protein kinase cascades, and reversible protein phosphorylation, ROS and redox homeostasis, direct defense, transcription machinery and protein turnover, cell wall remodeling, hormone biosynthesis, as well as immune molecule accumulation, are modulated during PTI and/or ETI, suggesting their common or specific roles in plant immune responses. However, NAC domain protein and lipid particle serine esterase, two PTI-specific genes from previous transcriptomic work, have not been detected as differentially regulated in our proteomic analysis, and they were proved to be not PTI-specific inducible and therefore cannot be used as PTI-reporters through “overlapping circle” pattern assay. These results provide insights into the fine-tuned regulatory mechanisms between PTI and ETI in-Pst pathosystem, which will springboard further investigations into the sophisticated mechanisms in plant immunity.
Project description:Seedlings of Arabidopsis wild type and ATE1/2 double knock-out mutants were treated with flagellin 22 peptide to elicit pathogen-triggered immunity (PTI) responses. Leaves were harvested and proteome composition assessed.
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:We develop a protocol for extracting P. syringae transcriptome from infected A. thaliana tissue through physical separation by low speed centrifugation. We use this protocol to compare the RNASeq transcriptome profiles of DC3000 during naïve host infection and exposure to pattern triggered immunity at 1, 3, and 5 hours post inoculation
Project description:Plants have evolved sophisticated mechanisms to regulate gene expression to activate immune responses against pathogen infections. However, how the translation system contributes to plant immunity is largely unknown. The evolutionarily conserved thiolation modification of tRNA ensures efficient decoding during translation. Here we show that tRNA thiolation is required for plant immunity in Arabidopsis. The Arabidopsis cgb mutant is hyper-susceptible to the pathogen Pseudomonas syringae. CGB encodes ROL5, a homolog of yeast NCS6 required for tRNA thiolation. ROL5 physically interacts with CTU2, a homolog of yeast NCS2. Mutations in either ROL5 or CTU2 result in loss of tRNA thiolation. Further analyses reveal that tRNA thiolation is required for both transcriptional reprogramming and translational reprogramming during immune responses. The translation efficiency of immune-related proteins reduces when tRNA thiolation is absent. Our study not only uncovers a new biological function of tRNA thiolation but also reveals a new mechanism for plant immunity.
Project description:The main goal of this study was to compare the differential efficiency of the antiviral activity triggered by externally delivered virus-specific and nonspecific dsRNAs in plants. RNAi mediated by virus-specific dsRNA is the main antiviral defense mechanism in plants, but nonspecific dsRNA-triggered responses have been documented to play a role in antiviral defense. Using PVX as a model, we have determined that co-inoculation with either virus-specific or nonspecific dsRNA reduced virus accumulation in both inoculated and systemic leaves although at different extent. While the administration of dsRNA specific for the targeted virus induced a potent RNAi-based antiviral response that resulted in highly effective control of viral disease, the degree of interference with PVX-GFP infection afforded by nonspecific dsRNA (PTI) was limited. To identify early biological processes and pathways associated with dsRNA-based immunity, we conducted a global transcriptome RNAseq assay from N. benthamiana leaves inoculated with four different treatments, i.e., dsGFP alone (dsG), PVX-GFP combined with dsGFP (dsG_VG), wild-type (Wt) PVX combined with dsGFP (dsG_V) and bacterial nucleic acid extracts not expressing dsRNA as a control (Ctr). KEGG analysis of differentially expressed genes showed a significant enrichment of terms related to plant-pathogen signaling pathways (KEGG terms Plant-pathogen interaction and MAPK signaling) in all the three treatments with dsRNA. Our results further indicate that the transcriptomic response triggered by dsRNA alone includes canonical immune pathways or genes known to be involved in defense responses, i.e., Ca+2 signaling, ethylene signaling, MAPK signaling, WRKY transcription factors, PR transcriptional factors, NBS-LRR resistance genes, EDS1, and LRR receptor-like kinases, many of which are typical of antimicrobial PTI . Moreover, the transcriptomic response to the homologous combination (dsGFP plus PVX-GFP) had a greater overrepresentation of genes involved in plant-pathogen signaling pathways than the heterologous combination (dsGFP plus Wt PVX), highlighting a quantitative difference between RNAi and PTI immune responses.
Project description:Plants have evolved sophisticated mechanisms to regulate gene expression to activate immune responses against pathogen infections. However, how the translation system contributes to plant immunity is largely unknown. The evolutionarily conserved thiolation modification of tRNA ensures efficient decoding during translation. Here we show that tRNA thiolation is required for plant immunity in Arabidopsis. The Arabidopsis cgb mutant is hyper-susceptible to the pathogen Pseudomonas syringae. CGB encodes ROL5, a homolog of yeast NCS6 required for tRNA thiolation. ROL5 physically interacts with CTU2, a homolog of yeast NCS2. Mutations in either ROL5 or CTU2 result in loss of tRNA thiolation. Further analyses reveal that tRNA thiolation is required for both transcriptional reprogramming and translational reprogramming during immune responses. The translation efficiency of immune-related proteins reduces when tRNA thiolation is absent. Our study not only uncovers a new biological function of tRNA thiolation but also reveals a new mechanism for plant immunity.