The plant immune system involves cell-surface receptors that detect intercellular pathogen-derived molecules, and intracellular receptors that activate immunity upon detection of pathogen-secreted ...effector proteins that act inside the plant cell. Immunity mediated by surface receptors has been extensively studied
, but that mediated by intracellular receptors has rarely been investigated in the absence of surface-receptor-mediated immunity. Furthermore, interactions between these two immune pathways are poorly understood. Here, by activating intracellular receptors without inducing surface-receptor-mediated immunity, we analyse interactions between these two distinct immune systems in Arabidopsis. Pathogen recognition by surface receptors activates multiple protein kinases and NADPH oxidases, and we find that intracellular receptors primarily potentiate the activation of these proteins by increasing their abundance through several mechanisms. Likewise, the hypersensitive response that depends on intracellular receptors is strongly enhanced by the activation of surface receptors. Activation of either immune system alone is insufficient to provide effective resistance against the bacterial pathogen Pseudomonas syringae. Thus, immune pathways activated by cell-surface and intracellular receptors in plants mutually potentiate to activate strong defences against pathogens. These findings reshape our understanding of plant immunity and have broad implications for crop improvement.
Plant pathogens compromise crop yields. Plants have evolved robust innate immunity that depends in part on intracellular Nucleotide‐binding, Leucine rich‐Repeat (NLR) immune receptors that activate ...defense responses upon detection of pathogen‐derived effectors. Most “sensor” NLRs that detect effectors require the activity of “helper” NLRs, but how helper NLRs support sensor NLR function is poorly understood. Many Solanaceae NLRs require NRC (NLR‐Required for Cell death) class of helper NLRs. We show here that Rpi‐amr3, a sensor NLR from Solanum americanum, detects AVRamr3 from the potato late blight pathogen, Phytophthora infestans, and activates oligomerization of helper NLRs NRC2 and NRC4 into high‐molecular‐weight resistosomes. In contrast, recognition of P. infestans effector AVRamr1 by another sensor NLR Rpi‐amr1 induces formation of only the NRC2 resistosome. The activated NRC2 oligomer becomes enriched in membrane fractions. ATP‐binding motifs of both Rpi‐amr3 and NRC2 are required for NRC2 resistosome formation, but not for the interaction of Rpi‐amr3 with its cognate effector. NRC2 resistosome can be activated by Rpi‐amr3 upon detection of AVRamr3 homologs from other Phytophthora species. Mechanistic understanding of NRC resistosome formation will underpin engineering crops with durable disease resistance.
Synopsis
Plants can respond quickly upon detection of pathogen effectors (virulence factors) via activation of intracellular Nucleotide‐binding, Leucine Rich‐Repeat (NLR) immune receptors. This study identifies Solanaceae NLR pairs in which pathogen effector detection via the “sensor” NLR induces “helper” NLR oligomerization and activation.
Activation of sensor NLRs can trigger oligomerization of helper NLRs.
Sensor NLRs are not included in the helper NLR oligomer.
ATP/ADP‐binding sites of both sensor and helper NLRs are required for helper NLR oligomerization.
The sensor NLR Rpi‐amr3 can detect different alleles of the potato late blight pathogen effector AVRamr3, providing a versatile tool for engineering resistance in plants.
Plant “sensor” NLR immune receptors detect specific pathogen virulence factors and activate “helper” NLRs to form defense‐triggering resistosomes.
Nucleotide‐binding domain leucine‐rich repeat (NLR) immune receptors are important components of plant and metazoan innate immunity that can function as individual units or as pairs or networks. Upon ...activation, NLRs form multiprotein complexes termed resistosomes or inflammasomes. Although metazoan paired NLRs, such as NAIP/NLRC4, form hetero‐complexes upon activation, the molecular mechanisms underpinning activation of plant paired NLRs, especially whether they associate in resistosome hetero‐complexes, is unknown. In asterid plant species, the NLR required for cell death (NRC) immune receptor network is composed of multiple resistance protein sensors and downstream helpers that confer immunity against diverse plant pathogens. Here, we show that pathogen effector‐activation of the NLR proteins Rx (confers virus resistance), and Bs2 (confers bacterial resistance) leads to oligomerization of their helper NLR, NRC2. Activated Rx does not oligomerize or enter into a stable complex with the NRC2 oligomer and remains cytoplasmic. In contrast, activated NRC2 oligomers accumulate in membrane‐associated puncta. We propose an activation‐and‐release model for NLRs in the NRC immune receptor network. This points to a distinct activation model compared with mammalian paired NLRs.
Synopsis
In metazoan immunity, sensor‐helper NLR immune receptor pairs activate by forming inflammasome hetero‐complexes. This study shows that plant sensor NLRs trigger the oligomerization of downstream helper NLRs without forming a stable hetero‐complex.
Sensor NLRs perceive pathogen elicitors and subsequently mediate oligomerization of downstream helpers
Sensor NLRs are not integrated into the final activated resistosome.
Sensor NLRs trigger oligomerization and plasma membrane localization of their downstream helpers upon overexpression of pathogen derived molecules and during infection.
Upon infection, plant NRC2 and NRC4 form resistosome complexes in the plasma membrane which exclude their activated NRC‐dependent sensors.
ABSTRACT
A Rickettsia sp. was isolated from the blood of a patient with an acute febrile illness using the shell vial technique; the isolate was named CN45Kr and was identified by molecular assay as ...Rickettsia monacensis, which was first recognized as a pathogen in Spain. Sequencing analysis showed that the gltA sequence of the isolate was identical to that of Rickettsia sp. IRS3. The ompA‐5mp fragment sequence showed 100% identity to those of R. monacensis and Rickettsia sp. In56 and ompA‐3pA In56 and 100% identity to that of Rickettsia sp. IRS3. The ompB sequence was found to have 99.9% similarity to that of R. monacensis IrR/Munich. This study confirms the pathogenicity of this agent and provides additional information about its geographic distribution.
This study investigated the effect of sandblasting particle size on the surface topography and compressive stresses of conventional zirconia (3 mol% yttria-stabilized tetragonal zirconia polycrystal; ...3Y-TZP) and two highly translucent zirconia (4 or 5 mol% partially stabilized zirconia; 4Y-PSZ or 5Y-PSZ). Plate-shaped zirconia specimens (14.0 × 14.0 × 1.0 mm3, n = 60 for each grade) were sandblasted using different Al2O3 sizes (25, 50, 90, 110, and 125 μm) under 0.2 MPa for 10 s/cm2 at a 10 mm distance and a 90° angle. The surface topography was characterized using a 3-D confocal laser microscopy and inspected with a scanning electron microscope. To assess residual stresses, the tetragonal peak shift at 147 cm−1 was traced using micro-Raman spectroscopy. Al2O3 sandblasting altered surface topographies (p < 0.05), although highly translucent zirconia showed more pronounced changes compared to conventional zirconia. 5Y-PSZ abraded with 110 μm sand showed the highest Sa value (0.76 ± 0.12 μm). Larger particle induced more compressive stresses for 3Y-TZP (p < 0.05), while only 25 μm sand induced residual stresses for 5Y-PSZ. Al2O3 sandblasting with 110 μm sand for 3Y-TZP, 90 μm sand for 4Y-PSZ, and 25 μm sand for 5Y-PSZ were considered as the recommended blasting conditions.
People are often reluctant to comply with social causes because doing so may involve personal sacrifices of time, money, and effort for benefits that are shared by other members of society. In an ...effort to increase compliance, government agencies and public institutions sometimes employ financial tools to promote social causes. However, employing financial tools to induce prosocial behavior is expensive and often ineffective. We propose that anthropomorphizing a social cause is a practical and inexpensive tool for increasing compliance with it. Across three prosocial contexts, we found that individuals exposed to a message from an anthropomorphized social cause, compared with individuals exposed to a message relating to a nonanthropomorphized social cause, were more willing to comply with the message. This effect was mediated by feelings of anticipatory guilt experienced when they considered the likely consequences of not complying with the cause. The theoretical and practical implications of these findings are discussed.
The Arabidopsis immune receptors RPS4 and RRS1 interact to co-confer responsiveness to bacterial effectors. The RRS1-R allele, with RPS4, responds to AvrRps4 and PopP2, whereas RRS1-S responds only ...to AvrRps4. Here, we show that the C terminus of RRS1-R but not RRS1-S is phosphorylated. Phosphorylation at Thr1214 in the WRKY domain maintains RRS1-R in its inactive state and also inhibits acetylation of RRS1-R by PopP2. PopP2 in turn catalyzes O-acetylation at the same site, thereby preventing its phosphorylation. Phosphorylation at other sites is required for PopP2 but not AvrRps4 responsiveness and facilitates the interaction of RRS1’s C terminus with its TIR domain. Derepression of RRS1-R or RRS1-S involves effector-triggered proximity between their TIR domain and C termini. This effector-promoted interaction between these domains relieves inhibition of TIRRPS4 by TIRRRS1. Our data reveal effector-triggered and phosphorylation-regulated conformational changes within RRS1 that results in distinct modes of derepression of the complex by PopP2 and AvrRps4.
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•Arabidopsis RRS1-R WRKY domain Thr phosphorylation is required for autoinhibition•Other RRS1-R C-terminal phosphorylation sites are required for PopP2 responsiveness•RRS1 derepression involves effector-enhanced proximity of TIRRRS1 to its C terminus•Enhanced TIRRRS1 and C terminus proximity relieves inhibition of TIRRRS1 on TIRRPS4
The Arabidopsis RRS1-R/RPS4 immune receptor complex responds to bacterial effectors AvrRps4 and PopP2. Guo et al. show that effector-enhanced RRS1 N- and C-terminal proximity comprises a critical reconfiguration step involved in derepression of the complex. Further, RRS1-R C-terminal phosphorylation-dependent conformational reconfigurations distinguish responsiveness to the two effectors.
Photomorphogenesis, light-mediated development, is an essential feature of all terrestrial plants. While chloroplast development and brassinosteroid (BR) signaling are known players in ...photomorphogenesis, proteins that regulate both pathways have yet to be identified. Here we report that DE-ETIOLATION IN THE DARK AND YELLOWING IN THE LIGHT (DAY), a membrane protein containing DnaJ-like domain, plays a dual-role in photomorphogenesis by stabilizing the BR receptor, BRI1, as well as a key enzyme in chlorophyll biosynthesis, POR. DAY localizes to both the endomembrane and chloroplasts via its first transmembrane domain and chloroplast transit peptide, respectively, and interacts with BRI1 and POR in their respective subcellular compartments. Using genetic analysis, we show that DAY acts independently on BR signaling and chlorophyll biogenesis. Collectively, this work uncovers DAY as a factor that simultaneously regulates BR signaling and chloroplast development, revealing a key regulator of photomorphogenesis that acts across cell compartments.
Tap46, a regulatory subunit of protein phosphatase 2A (PP2A), plays an essential role in plant growth and development through a functional link with the Target of Rapamycin (TOR) signalling pathway. ...Here, we have characterized the molecular mechanisms behind a gain-of-function phenotype of Tap46 and its relationship with TOR to gain further insights into Tap46 function in plants. Constitutive overexpression of Tap46 in Arabidopsis resulted in overall growth stimulation with enlarged organs, such as leaves and siliques. Kinematic analysis of leaf growth revealed that increased cell size was mainly responsible for the leaf enlargement. Tap46 overexpression also enhanced seed size and viability under accelerated ageing conditions. Enhanced plant growth was also observed in dexamethasone (DEX)-inducible Tap46 overexpression Arabidopsis lines, accompanied by increased cellular activities of nitrate-assimilating enzymes. DEX-induced Tap46 overexpression and Tap46 RNAi resulted in increased and decreased phosphorylation of S6 kinase (S6K), respectively, which is a sensitive indicator of endogenous TOR activity, and Tap46 interacted with S6K in planta based on bimolecular fluorescence complementation and co-immunoprecipitation. Furthermore, inactivation of TOR by estradiol-inducible RNAi or rapamycin treatment decreased Tap46 protein levels, but increased PP2A catalytic subunit levels. Real-time quantitative PCR analysis revealed that Tap46 overexpression induced transcriptional modulation of genes involved in nitrogen metabolism, ribosome biogenesis, and lignin biosynthesis. These findings suggest that Tap46 modulates plant growth as a positive effector of the TOR signalling pathway and Tap46/PP2Ac protein abundance is regulated by TOR activity.
Numerous efforts have been made to measure tastes for various purposes. However, most taste information is still obtained by human sensory evaluation. It is difficult to quantify a degree of taste or ...establish taste standard. Although artificial taste sensors called electronic tongues utilizing synthetic materials such as polymers, semiconductors, or lipid membranes have been developed, they have limited performance due to their low sensitivity and specificity. Recently, bioelectronic tongues fabricated by integrating human taste receptors and nanomaterial-based sensor platforms have been found to have high performance for measuring tastes with human-like taste perception. However, human umami taste receptor is heterodimeric class C GPCR composed of human taste receptor type 1 member 1 (T1R1) and member 3 (T1R3). Such complicated structure makes it difficult to fabricate bioelectronic tongue. The objective of this study was to develop a protein-based bioelectronic tongue for detecting and discriminating umami taste with human-like performance using umami ligand binding domain called venus flytrap (VFT) domain originating from T1R1 instead of using the whole heterodimeric complex of receptors. Such T1R1 VFT was produced from Escherichia coli (E. coli) with purification and refolding process. It was then immobilized onto graphene-based FET. This bioelectronic tongue for umami taste (BTUT) was able to detect monosodium L-glutamate (MSG) with high sensitivity (ca. 1 nM) and specificity in real-time. The intensity of umami taste was enhanced by inosine monophosphate (IMP) that is very similar to the human taste system. In addition, BTUT allowed efficient reusable property and storage stability. It maintained 90% of normalized signal intensity for five weeks. To develop bioelectronic tongue, this approach using the ligand binding domain of human taste receptor rather than the whole heterodimeric GPCRs has advantages in mass production, reusability, and stability. It also has great potential for various industrial applications such as food, beverage, and pharmaceutical fields.
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•Expression, purification and functional reconstitution of ligand binding domain of umami taste receptor.•Taste sensor for umami taste detection using T1R1 VFT-functionalized graphene-FET.•Bioelectronic tongue can detect the taste of umami with high sensitivity and selectivity.•Bioelectronic tongue can measure the enhancing effect like human taste system.
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