Single‐atom catalysts have emerged as an efficient oxidant activator for eliminating organic pollutants in Fenton‐like systems. However, the complex preparation, single active site, lack of ...understanding of the fundamental mechanism, and harsh pH conditions currently limit their practical applications. In this work, single‐atom iron anchored nitrogen‐rich g‐C3N4 nanotubes (FeCNs) are designed and synthesized by a facile approach, and eco‐friendly peracetic acid (PAA) is selected as the oxidant for Fenton‐like reactions. The constructed heterogenous system achieves an enhanced degradation of various organic contaminants over a wide pH range of 3.0–9.0, exhibiting an ultrahigh and stable catalytic activity, outperforming equivalent quantities of pristine g‐C3N4 by 75 times. The 18O isotope‐labeling technique, probe method, and theoretical calculations demonstrate that the efficient catalytic activity relies on the high‐valency iron‐oxo species coupled with organic radicals generated by PAA. An increase in electron transport from the contaminant to the formed “metastable PAA/FeCN catalyst surface complex” is detected. A double driving mechanism for the tubular g‐C3N4 regulated by a single Fe site and PAA activation is proposed. This work opens an avenue for developing novel catalysts with the coexistence of multiple active units and providing opportunities for significantly improving catalytic efficiency.
Atomically dispersing Fe(III) sites into fine‐tuned nitrogen‐rich graphitic carbon nitride nanotubes are designed for peracetic acid activation and further for Fenton‐like reactions. This work opens a new avenue to develop heterogenous catalytic systems with higher reactivity and better durability using a double engine mechanism.
Receptor networks underpin plant immunity Wu, Chih-Hang; Derevnina, Lida; Kamoun, Sophien
Science (American Association for the Advancement of Science),
2018-Jun-22, 2018-06-22, 20180622, Letnik:
360, Številka:
6395
Journal Article
Recenzirano
Plant-pathogen coevolution led to complex immune receptor networks
Plants are attacked by a multitude of pathogens and pests, some of which cause epidemics that threaten food security. Yet a ...fundamental concept in plant pathology is that most plants are actively resistant to most pathogens and pests. Plants fend off their innumerable biotic foes primarily through innate immune receptors that detect the invading pathogens and trigger a robust immune response. The conceptual basis of such interactions was elegantly articulated by Harold H. Flor, who, in 1942, proposed the hypothesis that single genes in plants and pathogens define the outcome of their interactions; that is, a plant harboring a specific gene displays resistance against a pathogen that carries an interacting virulence gene (
1
). This gene-for-gene model was hugely insightful and influential—it has helped to guide applied and basic research on disease resistance. However, recent findings are taking the field beyond this simplified binary view of plant-pathogen interactions. Plants carry extremely diverse and dynamic repertoires of immune receptors that are interconnected in complex ways. Conversely, plant pathogens secrete a diversity of virulence proteins and metabolites called effectors, and pathogen genomics has revealed hundreds of effector genes in many species. These effectors have evidently evolved to favor pathogen infection and spread, but a subset of them inadvertently activate plant immune receptors. The emerging paradigm is that dynamic webs of genetic and biochemical networks underpin the early stages of plant-pathogen interactions.
Rapid (co-)evolution at multiple timescales is a hallmark of plant–microbe interactions. The mechanistic basis for the rapid evolution largely rests on the features of the genomes of the interacting ...partners involved. Here, we review recent insights into genomic characteristics and mechanisms that enable rapid evolution of both plants and phytopathogens. These comprise fresh insights in allelic series of matching pairs of resistance and avirulence genes, the generation of novel pathogen effectors, the recently recognised small RNA warfare, and genomic aspects of secondary metabolite biosynthesis. In addition, we discuss the putative contributions of permissive host environments, transcriptional plasticity and the role of ploidy on the interactions. We conclude that the means underlying the rapid evolution of plant–microbe interactions are multifaceted and depend on the particular nature of each interaction.
Nucleotide-binding domain leucine-rich repeat receptors (NLRs) play important roles in the innate immune systems of both plants and animals. Recent breakthroughs in NLR biochemistry and biophysics ...have revolutionized our understanding of how NLR proteins function in plant immunity. In this review, we summarize the latest findings in plant NLR biology and draw direct comparisons to NLRs of animals. We discuss different mechanisms by which NLRs recognize their ligands in plants and animals. The discovery of plant NLR resistosomes that assemble in a comparable way to animal inflammasomes reinforces the striking similarities between the formation of plant and animal NLR complexes. Furthermore, we discuss the mechanisms by which plant NLRs mediate immune responses and draw comparisons to similar mechanisms identified in animals. Finally, we summarize the current knowledge of the complex genetic architecture formed by NLRs in plants and animals and the roles of NLRs beyond pathogen detection.
Three rigid and structurally simple heterocyclic stilbene derivatives, (E)‐3H,3′H‐1,1′‐biisobenzofuranylidene‐3,3′‐dione, (E)‐3‐(3‐oxobenzoc thiophen‐1(3H)‐ylidene)isobenzofuran‐1(3H)‐one, and ...(E)‐3H,3′H‐1,1′‐bibenzoc thiophenylidene‐3,3′‐dione, are found to fluoresce in their neat solid phases, from upper (S2) and lowest (S1) singlet excited states, even at room temperature in air. Photophysical studies, single‐crystal structures, and theoretical calculations indicate that large energy gaps between S2 and S1 states (T2 and T1 states) as well as an abundance of intra and intermolecular hydrogen bonds suppress internal conversions of the upper excited states in the solids and make possible the fluorescence from S2 excited states (phosphorescence from T2 excited states). These results, including unprecedented fluorescence quantum yields (2.3–9.6 %) from the S2 states in the neat solids, establish a unique molecular skeleton for achieving multi‐colored emissions from upper excited states by “suppressing” Kasha's rule.
A unique molecular skeleton that exhibits multiple‐state emissions as neat, single‐component molecular solids at room temperature in air is reported. Mechanistic studies revealed that large energy gaps between S2 and S1 states, and an abundance of intramolecular/intermolecular hydrogen bonds, suppress internal conversions of the upper excited states in the solids and enable unprecedented fluorescence quantum yields (2.3–9.6 %) from the S2 states.
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.
In this paper, the inverse problem of initial value identification for homogeneous anomalous diffusion equation with Riemann‐Liouville fractional derivative in time is studied. We prove that this ...kind of problem is ill‐posed. We analyze the optimal error bound of the problem under the source condition and apply the quasi‐boundary regularization method, fractional Landweber iterative regularization method, and Landweber iterative regularization method to solve this inverse problem. Based on the results of conditional stability, the error estimates between the exact solution and the regular solution are given under the priori and posteriori regularization parameter selection rules. Finally, three examples are given to illustrate the effectiveness and feasibility of these methods.
Both plants and animals rely on nucleotide-binding domain and leucine-rich repeat-containing (NLR) proteins to respond to invading pathogens and activate immune responses. An emerging concept of NLR ...function is that “sensor” NLR proteins are paired with “helper” NLRs to mediate immune signaling. However, our fundamental knowledge of sensor/helper NLRs in plants remains limited. In this study, we discovered a complex NLR immune network in which helper NLRs in the NRC (NLR required for cell death) family are functionally redundant but display distinct specificities toward different sensor NLRs that confer immunity to oomycetes, bacteria, viruses, nematodes, and insects. The helper NLR NRC4 is required for the function of several sensor NLRs, including Rpi-blb2, Mi-1.2, and R1, whereas NRC2 and NRC3 are required for the function of the sensor NLR Prf. Interestingly, NRC2, NRC3, and NRC4 redundantly contribute to the immunity mediated by other sensor NLRs, including Rx, Bs2, R8, and Sw5. NRC family and NRC-dependent NLRs are phylogenetically related and cluster into a well-supported superclade. Using extensive phylogenetic analysis, we discovered that the NRC superclade probably emerged over 100 Mya from an NLR pair that diversified to constitute up to one-half of the NLRs of asterids. These findings reveal a complex genetic network of NLRs and point to a link between evolutionary history and the mechanism of immune signaling. We propose that this NLR network increases the robustness of immune signaling to counteract rapidly evolving plant pathogens.
Objective
We analyzed the impact of mind mapping on the critical thinking ability of clinical nursing students and its use as a teaching application. This study provides reference information for ...clinical teaching.
Methods
We selected 64 nursing students using convenience sampling. Participants received basic knowledge training of mind mapping in three sessions during the intervention. Questionnaires on critical thinking ability were designed by the researchers, adopting the Chinese version of the Critical Thinking Disposition Inventory. Data collected using the questionnaires included learning strategy function and clinical skill improvement with mind mapping, as well as students’ degree of adaptability to mind mapping. Participants’ critical thinking ability before and after the intervention was analyzed using a paired t-test.
Results
The critical thinking inclination of nursing students was significantly improved after intervention compared with that before the intervention (t = −0.74). The four dimensions of open-mindedness, inquisitiveness, cognitive maturity, and systematicity among nursing students after the intervention were also significantly improved compared with before the intervention.
Conclusion
Mind mapping is conducive to improving the critical thinking ability of clinical nursing students.
The molecular codes underpinning the functions of plant NLR immune receptors are poorly understood. We used in vitro Mu transposition to generate a random truncation library and identify the minimal ...functional region of NLRs. We applied this method to NRC4-a helper NLR that functions with multiple sensor NLRs within a Solanaceae receptor network. This revealed that the NRC4 N-terminal 29 amino acids are sufficient to induce hypersensitive cell death. This region is defined by the consensus MADAxVSFxVxKLxxLLxxEx (MADA motif) that is conserved at the N-termini of NRC family proteins and ~20% of coiled-coil (CC)-type plant NLRs. The MADA motif matches the N-terminal α1 helix of Arabidopsis NLR protein ZAR1, which undergoes a conformational switch during resistosome activation. Immunoassays revealed that the MADA motif is functionally conserved across NLRs from distantly related plant species. NRC-dependent sensor NLRs lack MADA sequences indicating that this motif has degenerated in sensor NLRs over evolutionary time.
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