Biology subjects

Parker, J. E.

Publications and source records attributed to Parker, J. E..

30 records · Page 2Linked to original sources

bioRxiv2020

Pathogen effector recognition-dependent association of NRG1 with EDS1 and SAG101 in TNL receptor immunity

Plants utilise intracellular nucleotide-binding, leucine-rich repeat (NLR) immune receptors to detect pathogen effectors and activate local and systemic defence. NRG1 and ADR1 "helper" NLRs (RNLs), cooperate with enhanced disease susceptibility 1 (EDS1), senescence-associated gene 101 (SAG101) and phytoalexin-deficient 4 (PAD4) lipase-like proteins to mediate signalling from TIR domain NLR receptors (TNLs). However, the mechanism of RNL/EDS1-family protein cooperation is poorly understood. Here, we provide genetic and molecular evidence for exclusive EDS1/SAG101/NRG1 and EDS1/PAD4/ADR1 co-functions in TNL immunity. Using immunoprecipitation and mass spectrometry, we show effector recognition-dependent association of NRG1 with EDS1 and SAG101, but not PAD4. An EDS1-SAG101 complex associates with NRG1, and EDS1-PAD4 associates with ADR1, only in an immune-activated state. NRG1 requires an intact nucleotide-binding P-loop motif, and EDS1 a functional EP domain and its partner SAG101, for induced association and immunity. Thus, two distinct modules (NRG1/EDS1/SAG101 and ADR1/EDS1/PAD4) are required to execute TNL receptor defence signalling.

plant biology↗

bioRxiv2020

Arabidopsis cell surface LRR immune receptor signaling through the EDS1-PAD4-ADR1 node

Plants use both cell surface and intracellular immune receptors with leucine rich-repeat (LRRs) to detect pathogens. LRR receptor kinases (LRR-RKs) and LRR receptor-like proteins (LRR-RPs) recognize extracellular microbe-derived molecules to confer pattern-triggered immunity (PTI), while nucleotide-binding LRR (NLR) proteins detect microbial effectors inside the cell to confer effector-triggered immunity (ETI). Despite PTI and ETI signaling being initiated in different compartments, both rely on the transcriptional activation of similar sets of genes, suggesting convergence in signaling upstream of nuclear events. Here we report that two sets of molecules, helper NLRs from the ADR1 (ACTIVATED DISEASE RESISTANCE 1) family as well as lipase-like proteins EDS1 (ENHANCED DISEASE SUSCEPTIBILITY 1) and PAD4 (PHYTOALEXIN DEFICIENT 4), are required not only for ETI, but also for PTI. A further similarity is seen in the evolutionary patterns of some PTI and ETI receptor genes, with both often being highly polymorphic, and with nevertheless distinct roles of LRR-RK and LRR-RP receptors in immunity. We find that the LRR-RK SOBIR1 directly links LRR-RPs with the ADR1 helper NLR as well as EDS1 and PAD4, suggesting the formation of constitutive supramolecular signalosome complexes at the inner side of the plasma membrane. We propose that the EDS1-PAD4-ADR1 node is an essential component and convergence point for immune signaling cascades activated by both surface-resident LRR-RP receptors and intracellular NLR receptors.

plant biology↗

bioRxiv2020

Pattern recognition receptors confer plant salt tolerance via WRKY18/WRKY40 transcription factors

Pattern recognition receptors (PRRs) bind microbe- and damage-associated molecular patterns (MAMPs/DAMPs, respectively) to enhance host immunity in animals and plants. Here, we report that PRRs also confer salt tolerance in the model plant Arabidopsis thaliana following recognition of cognate ligands, such as bacterial flagellin and EF-Tu and the endogenous Pep peptides. Pattern-triggered salt tolerance (PTST) requires the PRR-associated kinases BAK1 and BIK1, and the NADPH oxidase RBOHD. Transcriptome profiling reveals an inventory of PTST target genes, which increase or acquire salt responsiveness following an exposure to immunogenic patterns. In their regulatory DNA sequences, specific binding sites for a subset of WRKY transcription factors are over-represented. Accordingly, PTST requires WRKY40 and WRKY18, which activate salt tolerance-related genes but attenuate pathogen defense-related genes, including the EDS1 immunity activator. PRR signaling leads to sustained WRKY40/WRKY18 accumulation under salt stress and utilizes both WRKYs for salt tolerance. The PRR-WRKY40/WRKY18 module also confers salt tolerance after challenge with non-pathogenic bacteria. Our findings give molecular insight into signaling plasticity underlying biotic-abiotic stress cross-tolerance in plants conferred by PRRs.

plant biology↗

bioRxiv2020

Downy Mildew effector HaRxL21 interacts with the transcriptional repressor TOPLESS to promote pathogen susceptibility

Hyaloperonospora arabidopsidis (Hpa) is an oomycete pathogen causing Arabidopsis downy mildew. Effector proteins secreted from the pathogen into the plant play key roles in promoting infection by suppressing plant immunity and manipulating the host to the pathogens advantage. One class of oomycete effectors share a conserved RxLR motif critical for their translocation into the host cell. Here we characterize the interaction between an RxLR effector, HaRxL21 (RxL21), and the Arabidopsis transcriptional co-repressor Topless (TPL). We establish that RxL21 and TPL interact via an EAR motif at the C-terminus of the effector, mimicking the host plant mechanism for recruiting TPL to sites of transcriptional repression. We show that this motif, and hence interaction with TPL, is necessary for the virulence function of the effector. Furthermore, we provide evidence that RxL21 uses the interaction with TPL, and its close relative TPL-related 1, to repress plant immunity and enhance host susceptibility to both biotrophic and necrotrophic pathogens.

plant biology↗

bioRxiv2020

Genome-wide chromatin binding of transcriptional corepressor Topless-related 1 in Arabidopsis

Timely and specific regulation of gene expression is critical for plant responses to environmental and developmental cues. Transcriptional coregulators have emerged as important factors in gene expression control, although they lack DNA-binding domains and the mechanisms by which they are recruited to and function at the chromatin are poorly understood. Plant Topless-related 1 (TPR1), belonging to a family of transcriptional corepressors found across eukaryotes, contributes to immunity signaling in Arabidopsis thaliana and wild tobacco. We performed chromatin immunoprecipitation and sequencing (ChIP-seq) on an Arabidopsis TPR1-GFP expressing transgenic line to characterize genome-wide TPR1-chromatin associations. The analysis revealed [~]1400 genes bound by TPR1, with the majority of binding sites located at gene upstream regions. Among the TPR1 bound genes, we find not only regulators of immunity but also genes controlling growth and development. To support further analysis of TPR1-chromatin complexes and other transcriptional corepressors in plants, we provide two ways to access the processed ChIP-seq data and enable their broader use by the research community.

plant biology↗

bioRxiv2020

A Novel Method for Calculating Beta Band Burst Durations in Parkinson's Disease Using a Physiological Baseline

BackgroundPathological bursts of neural activity in Parkinsons disease present as exaggerated subthalamic neuronal oscillations in the 8-30 Hz frequency range and are related to motor impairment. New MethodThis study introduces a novel method for determining burst dynamics using a baseline that matches physiological 1/f spectrum activity. We used resting state local field potentials from people with Parkinsons disease and a simulated 1/f signal to measure beta burst durations, to demonstrate how tuning parameters (i.e., bandwidth and center frequency) affect burst durations, to compare this with high power threshold methods, and to study the effect of increasing neurostimulation intensities on burst duration. ResultsBurst durations calculated using the Anderson method captured the longest and broadest distribution of burst durations in a pathological beta band compared to previous methods. Mean beta band burst durations were significantly shorter on compared to off neurostimulation (p = 0.011), and their distribution was shifted towards that of the physiological 1/f spectrum during increasing intensities of stimulation. Comparison with Existing MethodExisting methods of measuring local field potential power either lack temporal specificity to detect bursts (power spectral density diagrams and spectrograms) or include only higher power bursts and portions of the neural signal. ConclusionsWe suggest that this novel method is well suited to quantify the full range of fluctuations in beta band neural activity in the Parkinsonian brain. This method may reveal more relevant feedback biomarkers than averaged beta band power for future closed loop algorithms. HighlightsA novel method for measuring variability in subthalamic local field potential oscillations in Parkinsons disease using a physiological baseline of power. Modeling normal brain activity using a physiological 1/f spectrum. Burst durations depend on choice of bandwidth and center frequency. Defining an inert frequency band whose mean burst duration overlap the physiological 1/f spectrum, from which the baseline was determined. Burst durations progressively shortened during increasing intensities of deep brain stimulation.

neuroscience↗

bioRxiv2019

Arabidopsis ENHANCED DISEASE RESISTANCE1 Protein Kinase Regulates the Association of ENHANCED DISEASE SUSCEPTIBILITY1 and PHYTOALEXIN DEFICIENT4 to Inhibit Cell Death

ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1) and PHYTOALEXIN DEFICIENT4 (PAD4) are sequence-related lipase-like proteins that function as a complex to regulate defense responses in Arabidopsis by both salicylic acid-dependent and independent pathways. Here we describe a gain-of-function mutation in PAD4 (S135F) that enhances resistance and cell death in response to infection by the powdery mildew pathogen Golovinomyces cichoracearum. The mutant PAD4 protein accumulates to wild-type levels in Arabidopsis cells, thus these phenotypes are unlikely to be due to PAD4 over accumulation. The phenotypes are similar to loss of function mutations in the protein kinase Enhanced Disease Resistance1 (EDR1), and previous work has shown that loss of PAD4 or EDS1 suppresses edr1-mediated phenotypes, placing these proteins downstream of EDR1. Here we show that EDR1 directly associates with EDS1 and PAD4 and inhibits their interaction in yeast and plant cells. We propose a model whereby EDR1 negatively regulates defense responses by interfering with the heteromeric association of EDS1 and PAD4. Our data indicate that the S135F mutation likely alters an EDS1-independent function of PAD4, potentially shedding light on a yet unknown PAD4 signaling function.

plant biology↗

bioRxiv2019

Arabidopsis thaliana natural variation in temperature-modulated immunity uncovers transcription factor UNE12 as a thermoresponsive regulator

Temperature impacts plant immunity and growth but how temperature intersects with endogenous pathways remains unclear. Here we uncover variation between Arabidopsis thaliana natural accessions in response to two non-stress temperatures (22{degrees}C and 16{degrees}C) affecting accumulation of the thermoresponsive stress hormone salicylic acid (SA) and plant growth. Analysis of differentially responding A. thaliana accessions shows that pre-existing SA provides a benefit in limiting bacterial pathogen infection at both temperatures. Several A. thaliana genotypes display a capacity to mitigate negative effects of high SA on growth, indicating within-species plasticity in SA - growth tradeoffs. An association study of temperature x SA variation, followed by physiological and immunity phenotyping of mutant and over-expression lines, identifies the transcription factor unfertilized embryo sac 12 (UNE12) as a temperature-responsive SA immunity regulator. Here we reveal previously untapped diversity in plant responses to temperature and a way forward in understanding the genetic architecture of plant adaptation to changing environments.

plant biology↗

bioRxiv2019

Arabidopsis PAD4 lipase-like domain is a minimal functional unit in resistance to green peach aphid

Plants have evolved mechanisms to attract beneficial microbes and insects while protecting themselves against pathogenic microbes and pests. In Arabidopsis, the immune regulator PAD4 functions with its cognate partner EDS1 to limit pathogen growth. PAD4, independently of EDS1, reduces infestation by Green Peach Aphid (GPA). How PAD4 regulates these defense outputs is unclear. By expressing the N-terminal PAD4-lipase-like domain (LLD) without its C-terminal EDS1-PAD4 (EP) domain, we interrogated PAD4 functions in plant defense. Here we show that transgenic expression of PAD4LLD in Arabidopsis is sufficient for limiting GPA infestation, but not for conferring basal and effector-triggered pathogen immunity. This suggests that the C-terminal PAD4-EP domain is necessary for EDS1-dependent immune functions. Moreover, PAD4LLD is not sufficient to interact with EDS1, indicating the PAD4-EP domain is required for heterodimerisation. These data provide molecular evidence that PAD4 has domain specific functions.

plant biology↗

bioRxiv2019

Plant mixed lineage kinase domain-like proteins limit biotrophic pathogen growth

Mixed lineage kinase domain-like (MLKL) protein mediates necroptotic cell death in vertebrates. We report here the discovery of a conserved protein family across seed plants that is structurally homologous to vertebrate MLKL. The Arabidopsis thaliana genome encodes three MLKLs with overlapping functions in limiting growth of obligate biotrophic fungal and oomycete pathogens. Although displaying a cell death activity mediated by N-terminal helical bundles, termed HeLo domain, AtMLKL-dependent immunity can be separated from host cell death. Cryo-electron microscopy structures of AtMLKLs reveal a tetrameric configuration, in which the pseudokinase domain and brace region bury the HeLo-domains, indicative of an auto-repressed complex. We also show the association of two AtMLKLs with microtubules. These findings, coupled with resistance-enhancing activity and altered microtubule association of a phosphomimetic mutation in the pseudokinase domain of AtMLKL1, point to a cell death-independent immunity mechanism.\n\nOne Sentence SummaryPlants have a protein family that is structurally homologous to vertebrate mixed lineage kinase domain-like protein, which induces necroptotic cell death, but these plant proteins can confer immunity without host cell death.

plant biology↗

bioRxiv2019

A coevolved EDS1-SAG101-NRG1 module mediates cell death signaling by TIR-domain immune receptors

Plant intracellular nucleotide-binding/leucine-rich repeat (NLR) immune receptors are activated by pathogen effectors to trigger host defenses and cell death. Toll-Interleukin1-receptor (TIR)-domain NLRs (TNLs) converge on the Enhanced Disease Susceptibility1 (EDS1) family of lipase-like proteins for all resistance outputs. In Arabidopsis TNL immunity, AtEDS1 heterodimers with Phytoalexin Deficient4 (AtPAD4) transcriptionally boost basal defense pathways. AtEDS1 uses the same surface to interact with PAD4-related Senescence-Associated Gene101 (AtSAG101), but the role of AtEDS1-AtSAG101 heterodimers was unclear. We show that AtEDS1-AtSAG101 function together with AtNRG1 coiled-coil domain helper NLRs as a coevolved TNL cell death signaling module. AtEDS1-AtSAG101-AtNRG1 cell death activity is transferable to the solanaceous species, Nicotiana benthamiana, and cannot be substituted by AtEDS1-AtPAD4 with AtNRG1 or AtEDS1-AtSAG101 with endogenous NbNRG1. Analysis of EDS1-family evolutionary rate variation and heterodimer structure-guided phenotyping of AtEDS1 variants or AtPAD4-AtSAG101 chimeras identify closely aligned -helical coil surfaces in the AtEDS1-AtSAG101 partner C-terminal domains that are necessary for TNL cell death signaling. Our data suggest that TNL-triggered cell death and pathogen growth restriction are determined by distinctive features of EDS1-SAG101 and EDS1-PAD4 complexes and that these signaling machineries coevolved with further components within plant species or clades to regulate downstream pathways in TNL immunity.

plant biology↗

bioRxiv2018

An EDS1 EP-domain surface mediating timely transcriptional reprogramming of immunity genes

Plant intracellular NLR receptors recognize pathogen interference to trigger immunity. NLR signalling mechanisms have not been resolved. Enhanced disease susceptibility 1 (EDS1) heterodimers are recruited by Toll-interleukin1-receptor domain NLRs (TNLs) to transcriptionally mobilize resistance pathways. Using an Arabidopsis EDS1 heterodimer crystal structure we interrogate the conserved but functionally uncharacterized EDS1 -helical EP-domain. We identify EP-domain positively charged residues lining a cavity that are essential for TNL immunity signalling, beyond heterodimer formation. Mutating arginine (R493) to alanine creates a weak EDS1 allele which disables TNL immunity against bacteria producing a virulence factor, coronatine (COR). Arabidopsis plants expressing EDS1R493A are slow to mobilize defence gene expression changes, independently of COR. The transcriptional delay has severe consequences for pathogen resistance and for countering bacterial COR. We uncover a set of host immunity genes whose repression by COR is blocked by wild-type EDS1 but not by EDS1R493A in the TNL response. These data uncover an EDS1 signalling surface lining the heterodimer EP-domain cavity which confers timely transcriptional reprogramming of host defence pathways and blocks bacterial virulence in NLR receptor immunity.

plant biology↗