Project description:An important branch of plant immunity involves the recognition of pathogens by the NB-LRR proteins encoded by disease resistance genes. However, signaling events downstream of NB-LRR activation are poorly understood. We have analyzed the Arabidopsis translatome using ribosome affinity purification and RNAseq. Our results show that the translational status of hundreds of genes are differentially affected upon activation of the NB-LRR protein RPM1, showing an overall pattern of a switch away from growth-related activities to defense. Among these is the central translational regulator and growth promoter, TOR kinase. Suppression of TOR expression leads to increased resistance to pathogens while overexpression of TOR results in increased susceptibility, indicating an important role for translational control in the growth to defense switch. Furthermore, we show that several additional genes whose mRNAs are translationally regulated, including BIG, CCT2 and CIPK5, are required for plant innate immunity, identifying novel actors in plant defense.
Project description:Plant nucleotide-binding leucine-rich repeat (NB-LRR) disease resistance (R) proteins recognize specific “avirulent” pathogen effectors and activate immune responses. NB-LRR proteins structurally and functionally resemble mammalian Nod-like receptors (NLRs). How NB-LRR and NLR proteins activate defense is poorly understood. The divergently transcribed Arabidopsis R genes, RPS4 (resistance to Pseudomonas syringae 4) and RRS1 (resistance to Ralstonia solanacearum 1), function together to confer recognition of Pseudomonas AvrRps4 and Ralstonia PopP2. RRS1 is the only known recessive NB-LRR R gene and encodes a WRKY DNA binding domain, prompting suggestions that it acts downstream of RPS4 for transcriptional activation of defense genes. We define here the early RRS1-dependent transcriptional changes upon delivery of PopP2 via Pseudomonas type III secretion. The Arabidopsis slh1 (sensitive to low humidity 1) mutant encodes an RRS1 allele (RRS1SLH1) with a single amino acid (leucine) insertion in the WRKY DNA-binding domain. Its poor growth due to constitutive defense activation is rescued at higher temperature. Transcription profiling data indicate that RRS1SLH1-mediated defense activation overlaps substantially with AvrRps4- and PopP2-regulated responses. To better understand the genetic basis of RPS4/RRS1-dependent immunity, we performed a genetic screen to identify suppressor of slh1 immunity (sushi) mutants. We show that many sushi mutants carry mutations in RPS4, suggesting that RPS4 acts downstream or in a complex with RRS1. Interestingly, several mutations were identified in a domain C-terminal to the RPS4 LRR domain. Using an Agrobacterium-mediated transient assay system, we demonstrate that the P-loop motif of RPS4 but not of RRS1SLH1 is required for RRS1SLH1 function. We also recapitulate the dominant suppression of RRS1SLH1 defense activation by wild type RRS1 and show this suppression requires an intact RRS1 P-loop. These analyses of RRS1SLH1 shed new light on mechanisms by which NB-LRR protein pairs activate defense signaling, or are held inactive in the absence of a pathogen effector. Five weeks old Arabidopsis (Ws-2 and rrs1-1) leaves were infiltrated with Pf0-1 carrying PopP2 or PopP2C321A in pEDV6 and samples were collected at 2, 4, 6 and 8 hours post infiltration (hpi); mRNA profiles were generated in triplet, by deep sequencing on Illumina GAIIx using EXPRSS tag-seq protocol.
Project description:Plant nucleotide-binding leucine-rich repeat (NB-LRR) disease resistance (R) proteins recognize specific “avirulent” pathogen effectors and activate immune responses. NB-LRR proteins structurally and functionally resemble mammalian Nod-like receptors (NLRs). How NB-LRR and NLR proteins activate defense is poorly understood. The divergently transcribed Arabidopsis R genes, RPS4 (resistance to Pseudomonas syringae 4) and RRS1 (resistance to Ralstonia solanacearum 1), function together to confer recognition of Pseudomonas AvrRps4 and Ralstonia PopP2. RRS1 is the only known recessive NB-LRR R gene and encodes a WRKY DNA binding domain, prompting suggestions that it acts downstream of RPS4 for transcriptional activation of defense genes. We define here the early RRS1-dependent transcriptional changes upon delivery of PopP2 via Pseudomonas type III secretion. The Arabidopsis slh1 (sensitive to low humidity 1) mutant encodes an RRS1 allele (RRS1SLH1) with a single amino acid (leucine) insertion in the WRKY DNA-binding domain. Its poor growth due to constitutive defense activation is rescued at higher temperature. Transcription profiling data indicate that RRS1SLH1-mediated defense activation overlaps substantially with AvrRps4- and PopP2-regulated responses. To better understand the genetic basis of RPS4/RRS1-dependent immunity, we performed a genetic screen to identify suppressor of slh1 immunity (sushi) mutants. We show that many sushi mutants carry mutations in RPS4, suggesting that RPS4 acts downstream or in a complex with RRS1. Interestingly, several mutations were identified in a domain C-terminal to the RPS4 LRR domain. Using an Agrobacterium-mediated transient assay system, we demonstrate that the P-loop motif of RPS4 but not of RRS1SLH1 is required for RRS1SLH1 function. We also recapitulate the dominant suppression of RRS1SLH1 defense activation by wild type RRS1 and show this suppression requires an intact RRS1 P-loop. These analyses of RRS1SLH1 shed new light on mechanisms by which NB-LRR protein pairs activate defense signaling, or are held inactive in the absence of a pathogen effector.
Project description:Plant nucleotide-binding leucine-rich repeat (NB-LRR) disease resistance (R) proteins recognize specific “avirulent” pathogen effectors and activate immune responses. NB-LRR proteins structurally and functionally resemble mammalian Nod-like receptors (NLRs). How NB-LRR and NLR proteins activate defense is poorly understood. The divergently transcribed Arabidopsis R genes, RPS4 (resistance to Pseudomonas syringae 4) and RRS1 (resistance to Ralstonia solanacearum 1), function together to confer recognition of Pseudomonas AvrRps4 and Ralstonia PopP2. RRS1 is the only known recessive NB-LRR R gene and encodes a WRKY DNA binding domain, prompting suggestions that it acts downstream of RPS4 for transcriptional activation of defense genes. We define here the early RRS1-dependent transcriptional changes upon delivery of PopP2 via Pseudomonas type III secretion. The Arabidopsis slh1 (sensitive to low humidity 1) mutant encodes an RRS1 allele (RRS1SLH1) with a single amino acid (leucine) insertion in the WRKY DNA-binding domain. Its poor growth due to constitutive defense activation is rescued at higher temperature. Transcription profiling data indicate that RRS1SLH1-mediated defense activation overlaps substantially with AvrRps4- and PopP2-regulated responses. To better understand the genetic basis of RPS4/RRS1-dependent immunity, we performed a genetic screen to identify suppressor of slh1 immunity (sushi) mutants. We show that many sushi mutants carry mutations in RPS4, suggesting that RPS4 acts downstream or in a complex with RRS1. Interestingly, several mutations were identified in a domain C-terminal to the RPS4 LRR domain. Using an Agrobacterium-mediated transient assay system, we demonstrate that the P-loop motif of RPS4 but not of RRS1SLH1 is required for RRS1SLH1 function. We also recapitulate the dominant suppression of RRS1SLH1 defense activation by wild type RRS1 and show this suppression requires an intact RRS1 P-loop. These analyses of RRS1SLH1 shed new light on mechanisms by which NB-LRR protein pairs activate defense signaling, or are held inactive in the absence of a pathogen effector.
Project description:Plant nucleotide-binding leucine-rich repeat (NB-LRR) disease resistance (R) proteins recognize specific M-bM-^@M-^\avirulentM-bM-^@M-^] pathogen effectors and activate immune responses. NB-LRR proteins structurally and functionally resemble mammalian Nod-like receptors (NLRs). How NB-LRR and NLR proteins activate defense is poorly understood. The divergently transcribed Arabidopsis R genes, RPS4 (resistance to Pseudomonas syringae 4) and RRS1 (resistance to Ralstonia solanacearum 1), function together to confer recognition of Pseudomonas AvrRps4 and Ralstonia PopP2. RRS1 is the only known recessive NB-LRR R gene and encodes a WRKY DNA binding domain, prompting suggestions that it acts downstream of RPS4 for transcriptional activation of defense genes. We define here the early RRS1-dependent transcriptional changes upon delivery of PopP2 via Pseudomonas type III secretion. The Arabidopsis slh1 (sensitive to low humidity 1) mutant encodes an RRS1 allele (RRS1SLH1) with a single amino acid (leucine) insertion in the WRKY DNA-binding domain. Its poor growth due to constitutive defense activation is rescued at higher temperature. Transcription profiling data indicate that RRS1SLH1-mediated defense activation overlaps substantially with AvrRps4- and PopP2-regulated responses. To better understand the genetic basis of RPS4/RRS1-dependent immunity, we performed a genetic screen to identify suppressor of slh1 immunity (sushi) mutants. We show that many sushi mutants carry mutations in RPS4, suggesting that RPS4 acts downstream or in a complex with RRS1. Interestingly, several mutations were identified in a domain C-terminal to the RPS4 LRR domain. Using an Agrobacterium-mediated transient assay system, we demonstrate that the P-loop motif of RPS4 but not of RRS1SLH1 is required for RRS1SLH1 function. We also recapitulate the dominant suppression of RRS1SLH1 defense activation by wild type RRS1 and show this suppression requires an intact RRS1 P-loop. These analyses of RRS1SLH1 shed new light on mechanisms by which NB-LRR protein pairs activate defense signaling, or are held inactive in the absence of a pathogen effector. Arabidopsis No-0 and slh1 plants were grown for 4 weeks at 28M-BM-0C after germination on MS plate. Plants were transferred to 19M-BM-0C growth chamber at the beginning of the light cycle and samples were harvested at 0 h, 9 h, 12 h, 16 h and 24 h after transfer for total RNA extraction. mRNA profiles were generated by deep sequencing on Illumina GAIIx using EXPRSS tag-seq protocol. Please note that all 16 samples submitted for this study were sequenced in one lane of Illumina GAIIx and the "No-0_slh1_tempshift_nobarcode.fq" (linked to 'unassigned reads' sample) contains unassigned sequence reads, once sample de-multiplexing has been carried out based on barcode.
Project description:Plants have a large family of membrane receptor kinases (RKs) which sense extracellular signals to control plant growth, development, immunity, and stress response. The largest group of RKs contains an extracellular leucine-rich repeat (LRR) domain with over 200 members in Arabidopsis. However, the functional understanding of most of the LRR-RKs has been hampered by their genetic redundancy and the subtle phenotypes of RK overexpression. Here we show that the rapamycin-mediated heterodimerization of chimeric cytosolic kinase domains from receptor/co-receptor pairs in the plasma membrane can activate their downstream cellular signaling pathway, inducing the specific biological responses, including brassinosteroid, plant immunity, stomatal development, and lateral root development. This chemically controlled synthetic biology approach will be useful to investigate biological functions of LRR-RKs and their signaling pathways.
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:Innate immune responses of plant cells confer the first line of defence against pathogens. Signals generated by activated receptors are integrated inside the cell and converge on transcriptional programmes in the nucleus. The Arabidopsis Toll-related intracellular receptor RPS4 operates inside nuclei to trigger resistance to Pseudomonas bacteria expressing AvrRps4 and defence gene reprogramming through the stress response regulator, EDS1. In this immune response, RPS4 cooperates genetically with RRS1 encoding a nuclear TIR-NB-LRR receptor with an additional C-terminal ‘WRKY’ DNA-binding domain. Using transgenic Arabidopsis plants constitutively expressing RPS4 (35S:RPS4), an EDS1-dependent immune response can be turned on rapidly and synchronously in leaf cells after a switch from high (28°C) to moderate (19°C) temperature. In order to determine the relative contributions of RRS1 and EDS1 to temperature-conditioned 35S:RPS4-HS transcriptional reprogramming, we performed gene expression microarray analysis of 35S:RPS4-HS, 35S:RPS4-HS rrs1-11 and 35S:RPS4-HS eds1-2 leaf mRNAs before and after temperature shift. We used transgenic Arabidopsis plants over-expressing RPS4 in EDS1 WT, eds1-2 or rrs1-11 mutant backgrounds. 35S:RPS4, 35S:RPS4 eds1-2 and 35S:RPS4 rrs1-11 plants were grown at 28°C for 3.5 weeks, and subsequently shifted to 19°C. Samples were collected before shift (0h) and 2, 8 and 24h after shift, in triplicates.
Project description:Innate immune responses of plant cells confer the first line of defence against pathogens. Signals generated by activated receptors are integrated inside the cell and converge on transcriptional programmes in the nucleus. The Arabidopsis Toll-related intracellular receptor RPS4 operates inside nuclei to trigger resistance to Pseudomonas bacteria expressing AvrRps4 and defence gene reprogramming through the stress response regulator, EDS1. In this immune response, RPS4 cooperates genetically with RRS1 encoding a nuclear TIR-NB-LRR receptor with an additional C-terminal ‘WRKY’ DNA-binding domain. Using transgenic Arabidopsis plants constitutively expressing RPS4 (35S:RPS4), an EDS1-dependent immune response can be turned on rapidly and synchronously in leaf cells after a switch from high (28°C) to moderate (19°C) temperature. In order to determine the relative contributions of RRS1 and EDS1 to temperature-conditioned 35S:RPS4-HS transcriptional reprogramming, we performed gene expression microarray analysis of 35S:RPS4-HS, 35S:RPS4-HS rrs1-11 and 35S:RPS4-HS eds1-2 leaf mRNAs before and after temperature shift.
Project description:Trans-acting siRNAs (tasiRNAs) negatively regulate target transcripts and are characterized by siRNAs spaced in 21-nucleotide 'phased' intervals. TasiRNAs have not been extensively described in many plant species. We identified dozens of new miRNAs in Medicago and soybean and confirmed 119 Medicago targets. A search for phased tasiRNA-like small RNAs ('phasiRNAs') found at least 114 Medicago loci, the majority of which were NB-LRR encoding genes. Notably, conserved domains in NB-LRR-encoding RNAs are targeted by several 22-nt miRNA families to trigger phasiRNA production. DCL2 and SGS3 transcripts were also cleaved by these 22-nt miRNAs, generating phased small RNAs, suggesting synchronization between silencing and pathogen defense pathways. A second example of 'two-hit' phasiRNA processing was identified, utilizing miR156-miR172 sites. Our data illustrate a complex tasiRNA-mediated regulatory circuit that potentially modulates plant-microbe interactions. A few miRNA triggers regulate an extremely large gene family by targeting highly conserved protein motif-encoding sequences, representing a new paradigm for miRNA function.