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Special Issue "Plant Innate Immunity 3.0"

A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Molecular Plant Sciences".

Deadline for manuscript submissions: closed (31 December 2019).

Special Issue Editor

Prof. Dr. Marcello Iriti
E-Mail Website
Guest Editor
Department of Agricultural and Environmental Sciences, Milan State University, Milan, Italy
Interests: environmental pollution; agrochemicals; mycotoxins; biomonitoring
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Even if immunology has been purely regarded as a medical science, immunity represents a trait common to many living organisms. Classically, the mammalian immune system consists of innate and adaptive mechanisms that protect the host from pathogens; in particular, innate mechanisms function independently of previous exposure of the host to the infectious agent.

Animal and plant innate immunities share some similarities, and plants, as the animals, are capable of recognizing and distinguishing between self and non-self. Recognition by the innate immune system is based on germline-encoded receptors (also called pattern recognition receptors, PRRs) expressed on host cells which sense conserved structural components and metabolism products of fungi, bacteria and viruses (known as pathogen-associated molecular patterns, PAMPs) including lipids, polysaccharides, proteins and nucleic acids. During their evolutionary history, plants have developed various defence strategies in order to face pathogens. Although lacking immunoglobulin molecules, circulating cells and phagocytic processes, the effectors of the mammalian immunity, plants possess a rather complex and efficient innate immune system. Therefore, disease is a rare outcome in the spectrum of plant-microbe interactions because plants have (co)evolved a complex set of defence mechanisms to hinder pathogen challenging and, in most cases, prevent infection. The battery of defence reactions includes physical and chemical barriers, both preformed (or constitutive or passive) and inducible (or active), depending on whether they are pre-existing features of the plant or are switched on after challenging. When a pathogen is able to overcome these defences, disease ceases to be the exception.

We invite investigators to submit both original research and review articles that explore all the aspects of the plant innate immunity.

Potential topics include, but are not limited to:

  • Host resistance
  • Non-host resistance
  • Systemic acquired resistance (SAR)
  • Induced systemic resistance (ISR)
  • Plant-microbe interaction
  • Plant-insect interaction
  • Plant-nematode interaction
  • Elicitors
  • Plant activators
  • PAMPs/MAMPs/DAMPs (pathogen/microbe/damage-associated molecular patterns)
  • PRRs (pattern recognition receptors)
  • Hypersensitive response/Programmed cell death (PCD)
  • Phytoanticipins
  • Phytoalexins
  • Ribosome inactivating proteins
  • Pathogenesis-related (PR) proteins
  • Fitness costs

Related Special Issues:

Plant Innate Immunity (10 articles)
Plant Innate Immunity 2.0 (21 articles)

Plant Innate Immunity 4.0 (Ongoing)

Prof. Dr. Marcello Iriti
Guest Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. International Journal of Molecular Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

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Keywords

  • Crop protection
  • Plant diseases
  • Systemic acquired immunity
  • Defence metabolism
  • Secondary metabolites

Published Papers (14 papers)

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Research

Jump to: Review

Article
Characterization of the Biogenic Volatile Organic Compounds (BVOCs) and Analysis of the PR1 Molecular Marker in Vitis vinifera L. Inoculated with the Nematode Xiphinema index
Int. J. Mol. Sci. 2020, 21(12), 4485; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21124485 - 24 Jun 2020
Viewed by 786
Abstract
Upon pathogen attack, plants very quickly undergo rather complex physico-chemical changes, such as the production of new chemicals or alterations in membrane and cell wall properties, to reduce disease damages. An underestimated threat is represented by root parasitic nematodes. In Vitis vinifera L., [...] Read more.
Upon pathogen attack, plants very quickly undergo rather complex physico-chemical changes, such as the production of new chemicals or alterations in membrane and cell wall properties, to reduce disease damages. An underestimated threat is represented by root parasitic nematodes. In Vitis vinifera L., the nematode Xiphinema index is the unique vector of Grapevine fanleaf virus, responsible for fanleaf degeneration, one of the most widespread and economically damaging diseases worldwide. The aim of this study was to investigate changes in the emission of biogenic volatile organic compounds (BVOCs) in grapevines attacked by X. index. BVOCs play a role in plant defensive mechanisms and are synthetized in response to biotic damages. In our study, the BVOC profile was altered by the nematode feeding process. We found a decrease in β-ocimene and limonene monoterpene emissions, as well as an increase in α-farnesene and α-bergamotene sesquiterpene emissions in nematode-treated plants. Moreover, we evaluated the PR1 gene expression. The transcript level of PR1 gene was higher in the nematode-wounded roots, while in the leaf tissues it showed a lower expression compared to control grapevines. Full article
(This article belongs to the Special Issue Plant Innate Immunity 3.0)
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Article
Zinc and Copper Enhance Cucumber Tolerance to Fusaric Acid by Mediating Its Distribution and Toxicity and Modifying the Antioxidant System
Int. J. Mol. Sci. 2020, 21(9), 3370; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21093370 - 10 May 2020
Cited by 3 | Viewed by 793
Abstract
Fusaric acid (FA), the fungal toxin produced by Fusarium oxysporum, plays a predominant role in the virulence and symptom development of Fusarium wilt disease. As mineral nutrients can be protective agents against Fusarium wilt, hydroponic experiments employing zinc (Zn) and copper (Cu) [...] Read more.
Fusaric acid (FA), the fungal toxin produced by Fusarium oxysporum, plays a predominant role in the virulence and symptom development of Fusarium wilt disease. As mineral nutrients can be protective agents against Fusarium wilt, hydroponic experiments employing zinc (Zn) and copper (Cu) followed by FA treatment were conducted in a glasshouse. FA exhibited strong phytotoxicity on cucumber plants, which was reversed by the addition of Zn or Cu. Thus, Zn or Cu dramatically reduced the wilt index, alleviated the leaf or root cell membrane injury and mitigated against the FA inhibition of plant growth and photosynthesis. Cucumber plants grown with Zn exhibited decreased FA transportation to shoots and a 17% increase in toxicity mitigation and showed minimal hydrogen peroxide, lipid peroxidation level with the increased of antioxidant enzymes activity in both roots and leaves. Cucumber grown with additional Cu absorbed less FA but showed more toxicity mitigation at 20% compared to with additional Zn and exhibited decreased hydrogen peroxide level and increased antioxidant enzymes activity. Thus, adding Zn or Cu can decrease the toxicity of the FA by affecting the absorption or transportation of the FA in plants and mitigate toxicity possibly through chelation. Zn and Cu modify the antioxidant system to scavenge hydrogen peroxide for suppressing FA induction of oxidative damage. Our experiments could provide a theoretical basis for the direct application of micro-fertilizer as protective agents in farming. Full article
(This article belongs to the Special Issue Plant Innate Immunity 3.0)
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Article
Arabidopsis RETICULON-LIKE4 (RTNLB4) Protein Participates in Agrobacterium Infection and VirB2 Peptide-Induced Plant Defense Response
Int. J. Mol. Sci. 2020, 21(5), 1722; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21051722 - 03 Mar 2020
Cited by 1 | Viewed by 1327
Abstract
Agrobacterium tumefaciens uses the type IV secretion system, which consists of VirB1-B11 and VirD4 proteins, to deliver effectors into plant cells. The effectors manipulate plant proteins to assist in T-DNA transfer, integration, and expression in plant cells. The Arabidopsis reticulon-like (RTNLB) proteins are [...] Read more.
Agrobacterium tumefaciens uses the type IV secretion system, which consists of VirB1-B11 and VirD4 proteins, to deliver effectors into plant cells. The effectors manipulate plant proteins to assist in T-DNA transfer, integration, and expression in plant cells. The Arabidopsis reticulon-like (RTNLB) proteins are located in the endoplasmic reticulum and are involved in endomembrane trafficking in plant cells. The rtnlb4 mutants were recalcitrant to A. tumefaciens infection, but overexpression of RTNLB4 in transgenic plants resulted in hypersusceptibility to A. tumefaciens transformation, which suggests the involvement of RTNLB4 in A. tumefaciens infection. The expression of defense-related genes, including FRK1, PR1, WRKY22, and WRKY29, were less induced in RTNLB4 overexpression (O/E) transgenic plants after A. tumefaciens elf18 peptide treatment. Pretreatment with elf18 peptide decreased Agrobacterium-mediated transient expression efficiency more in wild-type seedlings than RTNLB4 O/E transgenic plants, which suggests that the induced defense responses in RTNLB4 O/E transgenic plants might be affected after bacterial elicitor treatments. Similarly, A. tumefaciens VirB2 peptide pretreatment reduced transient T-DNA expression in wild-type seedlings to a greater extent than in RTNLB4 O/E transgenic seedlings. Furthermore, the VirB2 peptides induced FRK1, WRKY22, and WRKY29 gene expression in wild-type seedlings but not efr-1 and bak1 mutants. The induced defense-related gene expression was lower in RTNLB4 O/E transgenic plants than wild-type seedlings after VirB2 peptide treatment. These data suggest that RTNLB4 may participate in elf18 and VirB2 peptide-induced defense responses and may therefore affect the A. tumefaciens infection process. Full article
(This article belongs to the Special Issue Plant Innate Immunity 3.0)
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Article
Oxathiapiprolin, a Novel Chemical Inducer Activates the Plant Disease Resistance
Int. J. Mol. Sci. 2020, 21(4), 1223; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21041223 - 12 Feb 2020
Cited by 3 | Viewed by 1089
Abstract
Oxathiapiprolin was developed as a specific plant pathogenic oomycete inhibitor, previously shown to have highly curative and protective activities against the pepper Phytophthora blight disease under field and greenhouse tests. Therefore, it was hypothesized that oxathiapiprolin might potentially activate the plant disease resistance [...] Read more.
Oxathiapiprolin was developed as a specific plant pathogenic oomycete inhibitor, previously shown to have highly curative and protective activities against the pepper Phytophthora blight disease under field and greenhouse tests. Therefore, it was hypothesized that oxathiapiprolin might potentially activate the plant disease resistance against pathogen infections. This study investigated the potential and related mechanism of oxathiapiprolin to activate the plant disease resistance using the bacterium Pseudomonas syringae pv tomato (Pst) and plant Arabidopsis interaction as the targeted system. Our results showed that oxathiapiprolin could activate the plant disease resistance against Pst DC3000, a non-target pathogen of oxathiapiprolin, in Arabidopsis, tobacco, and tomato plants. Our results also showed the enhanced callose deposition and H2O2 accumulation in the oxathiapiprolin-treated Arabidopsis under the induction of flg22 as the pathogen-associated molecular pattern (PAMP) treatment. Furthermore, increased levels of free salicylic acid (SA) and jasmonic acid (JA) were detected in the oxathiapiprolin-treated Arabidopsis plants compared to the mock-treated ones under the challenge of Pst DC3000. Besides, the gene expression results confirmed that at 24 h after the infiltration with Pst DC3000, the oxathiapiprolin-treated Arabidopsis plants had upregulated expression levels of the respiratory burst oxidase homolog D (RBOHD), JA-responsive gene (PDF1.2), and SA-responsive genes (PR1, PR2, and PR5) compared to the control. Taken together, oxathiapiprolin is identified as a novel chemical inducer which activates the plant disease resistance against Pst DC3000 by enhancing the callose deposition, H2O2 accumulation, and hormone SA and JA production. Full article
(This article belongs to the Special Issue Plant Innate Immunity 3.0)
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Article
Transcriptomic Insights into Innate Immunity Responding to Red Rot Disease in Red Alga Pyropia yezoensis
Int. J. Mol. Sci. 2019, 20(23), 5970; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms20235970 - 27 Nov 2019
Cited by 4 | Viewed by 1174
Abstract
Pyropia yezoensis, one of the most economically important marine algae, suffers from the biotic stress of the oomycete necrotrophic pathogen Pythium porphyrae. However, little is known about the molecular defensive mechanisms employed by Pyr. yezoensis during the infection process. In the [...] Read more.
Pyropia yezoensis, one of the most economically important marine algae, suffers from the biotic stress of the oomycete necrotrophic pathogen Pythium porphyrae. However, little is known about the molecular defensive mechanisms employed by Pyr. yezoensis during the infection process. In the present study, we defined three stages of red rot disease based on histopathological features and photosynthetic physiology. Transcriptomic analysis was carried out at different stages of infection to identify the genes related to the innate immune system in Pyr. yezoensis. In total, 2139 up-regulated genes and 1672 down-regulated genes were identified from all the infected groups. Pathogen receptor genes, including three lectin genes (pattern recognition receptors (PRRs)) and five genes encoding typical plant R protein domains (leucine rich repeat (LRR), nucleotide binding site (NBS), or Toll/interleukin-1 receptor (TIR)), were found to be up-regulated after infection. Several defense mechanisms that were typically regarded as PAMP-triggered immunity (PTI) in plants were induced during the infection. These included defensive and protective enzymes, heat shock proteins, secondary metabolites, cellulase, and protease inhibitors. As a part of the effector-triggered immunity (ETI), the expression of genes related to the ubiquitin-proteasome system (UPS) and hypersensitive cell death response (HR) increased significantly during the infection. The current study suggests that, similar to plants, Pyr. yezoensis possesses a conserved innate immune system that counters the invasion of necrotrophic pathogen Pyt. porphyrae. However, the innate immunity genes of Pyr. yezoensis appear to be more ancient in origin compared to those in higher plants. Full article
(This article belongs to the Special Issue Plant Innate Immunity 3.0)
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Article
Proteomics of PTI and Two ETI Immune Reactions in Potato Leaves
Int. J. Mol. Sci. 2019, 20(19), 4726; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms20194726 - 24 Sep 2019
Cited by 4 | Viewed by 2569
Abstract
Plants have a variety of ways to defend themselves against pathogens. A commonly used model of the plant immune system is divided into a general response triggered by pathogen-associated molecular patterns (PAMPs), and a specific response triggered by effectors. The first type of [...] Read more.
Plants have a variety of ways to defend themselves against pathogens. A commonly used model of the plant immune system is divided into a general response triggered by pathogen-associated molecular patterns (PAMPs), and a specific response triggered by effectors. The first type of response is known as PAMP triggered immunity (PTI), and the second is known as effector-triggered immunity (ETI). To obtain better insight into changes of protein abundance in immunity reactions, we performed a comparative proteomic analysis of a PTI and two different ETI models (relating to Phytophthora infestans) in potato. Several proteins showed higher abundance in all immune reactions, such as a protein annotated as sterol carrier protein 2 that could be interesting since Phytophthora species are sterol auxotrophs. RNA binding proteins also showed altered abundance in the different immune reactions. Furthermore, we identified some PTI-specific changes of protein abundance, such as for example, a glyoxysomal fatty acid beta-oxidation multifunctional protein and a MAR-binding protein. Interestingly, a lysine histone demethylase was decreased in PTI, and that prompted us to also analyze protein methylation in our datasets. The proteins upregulated explicitly in ETI included several catalases. Few proteins were regulated in only one of the ETI interactions. For example, histones were only downregulated in the ETI-Avr2 interaction, and a putative multiprotein bridging factor was only upregulated in the ETI-IpiO interaction. One example of a methylated protein that increased in the ETI interactions was a serine hydroxymethyltransferase. Full article
(This article belongs to the Special Issue Plant Innate Immunity 3.0)
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Article
The Highly Conserved Barley Powdery Mildew Effector BEC1019 Confers Susceptibility to Biotrophic and Necrotrophic Pathogens in Wheat
Int. J. Mol. Sci. 2019, 20(18), 4376; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms20184376 - 06 Sep 2019
Cited by 2 | Viewed by 1325
Abstract
Effector proteins secreted by plant pathogens play important roles in promoting colonization. Blumeria effector candidate (BEC) 1019, a highly conserved metalloprotease of Blumeria graminis f. sp. hordei (Bgh), is essential for fungal haustorium formation, and silencing BEC1019 significantly reduces [...] Read more.
Effector proteins secreted by plant pathogens play important roles in promoting colonization. Blumeria effector candidate (BEC) 1019, a highly conserved metalloprotease of Blumeria graminis f. sp. hordei (Bgh), is essential for fungal haustorium formation, and silencing BEC1019 significantly reduces Bgh virulence. In this study, we found that BEC1019 homologs in B. graminis f. sp. tritici (Bgt) and Gaeumannomyces graminis var. tritici (Ggt) have complete sequence identity with those in Bgh, prompting us to investigate their functions. Transcript levels of BEC1019 were abundantly induced concomitant with haustorium formation in Bgt and necrosis development in Ggt-infected plants. BEC1019 overexpression considerably increased wheat susceptibility to Bgt and Ggt, whereas silencing this gene using host-induced gene silencing significantly enhanced wheat resistance to Bgt and Ggt, which was associated with hydrogen peroxide accumulation, cell death, and pathogenesis-related gene expression. Additionally, we found that the full and partial sequences of BEC1019 can trigger cell death in Nicotiana benthamiana leaves. These results indicate that Bgt and Ggt can utilize BEC1019 as a virulence effector to promote plant colonization, and thus these genes represent promising new targets in breeding wheat cultivars with broad-spectrum resistance. Full article
(This article belongs to the Special Issue Plant Innate Immunity 3.0)
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Article
Metabolomic Profiling of the Host Response of Tomato (Solanum lycopersicum) Following Infection by Ralstonia solanacearum
Int. J. Mol. Sci. 2019, 20(16), 3945; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms20163945 - 14 Aug 2019
Cited by 12 | Viewed by 1869
Abstract
Tomato (Solanum lycopersicum) is an important dietary source of bioactive phytochemicals and active breeding programs constantly produce new cultivars possessing superior and desirable traits. The phytopathogenic Ralstonia solanacearum, the causal agent of bacterial wilt, is a highly destructive bacterial disease [...] Read more.
Tomato (Solanum lycopersicum) is an important dietary source of bioactive phytochemicals and active breeding programs constantly produce new cultivars possessing superior and desirable traits. The phytopathogenic Ralstonia solanacearum, the causal agent of bacterial wilt, is a highly destructive bacterial disease with a high economic impact on tomato production. This study followed an untargeted metabolomic approach involving four tomato cultivars and aimed at the identification of secondary metabolites involved in plant defense after infection with R. solanacearum. Liquid chromatography coupled to mass spectrometry (LC-MS) in combination with multivariate data analysis and chemometric modelling were utilized for the identification of discriminant secondary metabolites. The total of 81 statistically selected features were annotated belonging to the metabolite classes of amino acids, organic acids, fatty acids, various derivatives of cinnamic acid and benzoic acids, flavonoids and steroidal glycoalkaloids. The results indicate that the phenylpropanoid pathway, represented by flavonoids and hydroxycinnamic acids, is of prime importance in the tomato defense response. The hydroxycinnamic acids esters of quinic acid, hexoses and glucaric acids were identified as signatory biomarkers, as well as the hydroxycinnamic acid amides to polyamines and tyramine. Interestingly, the rapid and differential accumulation of putrescine, dopamine, and tyramine derivatives, along with the presence of a newly documented metabolite, feruloyl serotonin, were documented in the infected plants. Metabolite concentration variability in the different cultivar tissues point to cultivar-specific variation in the speed and manner of resource redistribution between the host tissues. These metabolic phenotypes provide insights into the differential metabolic signatures underlying the defense metabolism of the four cultivars, defining their defensive capabilities to R. solanacearum. Full article
(This article belongs to the Special Issue Plant Innate Immunity 3.0)
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Article
Aphid-Triggered Changes in Oxidative Damage Markers of Nucleic Acids, Proteins, and Lipids in Maize (Zea mays L.) Seedlings
Int. J. Mol. Sci. 2019, 20(15), 3742; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms20153742 - 31 Jul 2019
Cited by 6 | Viewed by 1042
Abstract
Prior experiments illustrated reactive oxygen species (ROS) overproduction in maize plants infested with bird-cherry-oat (Rhopalosiphum padi L.) aphids. However, there is no available data unveiling the impact of aphids feeding on oxidative damages of crucial macromolecules in maize tissues. Therefore, the purpose [...] Read more.
Prior experiments illustrated reactive oxygen species (ROS) overproduction in maize plants infested with bird-cherry-oat (Rhopalosiphum padi L.) aphids. However, there is no available data unveiling the impact of aphids feeding on oxidative damages of crucial macromolecules in maize tissues. Therefore, the purpose of the current study was to evaluate the scale of oxidative damages of genomic DNA, total RNA and mRNA, proteins, and lipids in seedling leaves of two maize genotypes (Złota Karłowa and Waza cvs—susceptible and relatively resistant to the aphids, respectively). The content of oxidized guanosine residues (8-hydroxy-2′-deoxyguanosine; 8-OHdG) in genomic DNA, 8-hydroxyguanosine (8-OHG) in RNA molecules, protein carbonyl groups, total thiols (T-SH), protein-bound thiols (PB-SH), non-protein thiols (NP-SH), malondialdehyde (MDA) and electrolyte leakage (EL) levels in maze plants were determined. In addition, the electrical penetration graphs (EPG) technique was used to monitor and the aphid stylet positioning and feeding modes in the hosts. Maize seedlings were infested with 0 (control), 30 or 60 R. padi adult apterae per plant. Substantial increases in the levels of RNA, protein and lipid oxidation markers in response to aphid herbivory, but no significant oxidative damages of genomic DNA, were found. Alterations in the studied parameters were dependent on maize genotype, insect abundance and infestation time. Full article
(This article belongs to the Special Issue Plant Innate Immunity 3.0)
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Article
OsMKK3, a Stress-Responsive Protein Kinase, Positively Regulates Rice Resistance to Nilaparvata lugens via Phytohormone Dynamics
Int. J. Mol. Sci. 2019, 20(12), 3023; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms20123023 - 20 Jun 2019
Cited by 15 | Viewed by 1546
Abstract
Plants undergo several but very precise molecular, physiological, and biochemical modulations in response to biotic stresses. Mitogen-activated protein kinase (MAPK) cascades orchestrate multiple cellular processes including plant growth and development as well as plant responses against abiotic and biotic stresses. However, the role [...] Read more.
Plants undergo several but very precise molecular, physiological, and biochemical modulations in response to biotic stresses. Mitogen-activated protein kinase (MAPK) cascades orchestrate multiple cellular processes including plant growth and development as well as plant responses against abiotic and biotic stresses. However, the role of MAPK kinases (MAPKKs/MKKs/MEKs) in the regulation of plant resistance to herbivores has not been extensively investigated. Here, we cloned a rice MKK gene, OsMKK3, and investigated its function. It was observed that mechanical wounding, infestation of brown planthopper (BPH) Nilaparvata lugens, and treatment with methyl jasmonate (MeJA) or salicylic acid (SA) could induce the expression of OsMKK3. The over-expression of OsMKK3 (oe-MKK3) increased levels of jasmonic acid (JA), jasmonoyl-L-isoleucine (JA-Ile), and abscisic acid (ABA), and decreased SA levels in rice after BPH attack. Additionally, the preference for feeding and oviposition, the hatching rate of BPH eggs, and BPH nymph survival rate were significantly compromised due to over-expression of OsMKK3. Besides, oe-MKK3 also augmented chlorophyll content but impaired plant growth. We confirm that MKK3 plays a pivotal role in the signaling pathway. It is proposed that OsMKK3 mediated positive regulation of rice resistance to BPH by means of herbivory-induced phytohormone dynamics. Full article
(This article belongs to the Special Issue Plant Innate Immunity 3.0)
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Communication
Effects of Abscisic Acid and Salicylic Acid on Gene Expression in the Antiviral RNA Silencing Pathway in Arabidopsis
Int. J. Mol. Sci. 2019, 20(10), 2538; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms20102538 - 23 May 2019
Cited by 12 | Viewed by 2012
Abstract
The RNA silencing pathways modulate responses to certain stresses, and can be partially tuned by several hormones such as salicylic acid (SA) and abscisic acid (ABA). Although SA and ABA are often antagonistic and often modulate different stress responses, they have similar effects [...] Read more.
The RNA silencing pathways modulate responses to certain stresses, and can be partially tuned by several hormones such as salicylic acid (SA) and abscisic acid (ABA). Although SA and ABA are often antagonistic and often modulate different stress responses, they have similar effects on virus resistance, which are partially achieved through the antiviral RNA silencing pathway. Whether they play similar roles in regulating the RNA silencing pathway is unclear. By employing coexpression and promoter analyses, we found that some ABA- and SA-related transcription factors (TFs) are coexpressed with several AGO, DCL, and RDR genes, and have multiple binding sites for the identified TFs in the queried promoters. ABA and SA are antagonistic with respect to the expression of AGO1 and RDRs because ABA was able to induce these genes only in the SA mutant. Nevertheless, both hormones showed similarities in the regulation of other genes, for example, the induction of AGO2 by ABA was SA-dependent, indicating that ABA acts upstream of SA in this regulation. We inferred that the similar effects of ABA and SA on some genes resulted in the redundancy of their roles in resistance to bamboo mosaic virus, but that the two hormones are antagonistic with respect to other genes unrelated to their biosynthesis pathways. Full article
(This article belongs to the Special Issue Plant Innate Immunity 3.0)
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Review

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Review
Prospects of Gene Knockouts in the Functional Study of MAMP-Triggered Immunity: A Review
Int. J. Mol. Sci. 2020, 21(7), 2540; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21072540 - 06 Apr 2020
Cited by 3 | Viewed by 1327
Abstract
Plants depend on both preformed and inducible defence responses to defend themselves against biotic stresses stemming from pathogen attacks. In this regard, plants perceive pathogenic threats from the environment through pattern recognition receptors (PRRs) that recognise microbe-associated molecular patterns (MAMPs), and so induce [...] Read more.
Plants depend on both preformed and inducible defence responses to defend themselves against biotic stresses stemming from pathogen attacks. In this regard, plants perceive pathogenic threats from the environment through pattern recognition receptors (PRRs) that recognise microbe-associated molecular patterns (MAMPs), and so induce plant defence responses against invading pathogens. Close to thirty PRR proteins have been identified in plants, however, the molecular mechanisms underlying MAMP perception by these receptors/receptor complexes are not fully understood. As such, knockout (KO) of genes that code for PRRs and co-receptors/defence-associated proteins is a valuable tool to study plant immunity. The loss of gene activity often causes changes in the phenotype of the model plant, allowing in vivo studies of gene function and associated biological mechanisms. Here, we review the functions of selected PRRs, brassinosteroid insensitive 1 (BRI1) associated receptor kinase 1 (BAK1) and other associated defence proteins that have been identified in plants, and also outline KO lines generated by T-DNA insertional mutagenesis as well as the effect on MAMP perception—and triggered immunity (MTI). In addition, we further review the role of membrane raft domains in flg22-induced MTI in Arabidopsis, due to the vital role in the activation of several proteins that are part of the membrane raft domain theory in this regard. Full article
(This article belongs to the Special Issue Plant Innate Immunity 3.0)
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Review
Elicitor and Receptor Molecules: Orchestrators of Plant Defense and Immunity
Int. J. Mol. Sci. 2020, 21(3), 963; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21030963 - 31 Jan 2020
Cited by 38 | Viewed by 3048
Abstract
Pathogen-associated molecular patterns (PAMPs), microbe-associated molecular patterns (MAMPs), herbivore-associated molecular patterns (HAMPs), and damage-associated molecular patterns (DAMPs) are molecules produced by microorganisms and insects in the event of infection, microbial priming, and insect predation. These molecules are then recognized by receptor molecules on [...] Read more.
Pathogen-associated molecular patterns (PAMPs), microbe-associated molecular patterns (MAMPs), herbivore-associated molecular patterns (HAMPs), and damage-associated molecular patterns (DAMPs) are molecules produced by microorganisms and insects in the event of infection, microbial priming, and insect predation. These molecules are then recognized by receptor molecules on or within the plant, which activates the defense signaling pathways, resulting in plant’s ability to overcome pathogenic invasion, induce systemic resistance, and protect against insect predation and damage. These small molecular motifs are conserved in all organisms. Fungi, bacteria, and insects have their own specific molecular patterns that induce defenses in plants. Most of the molecular patterns are either present as part of the pathogen’s structure or exudates (in bacteria and fungi), or insect saliva and honeydew. Since biotic stresses such as pathogens and insects can impair crop yield and production, understanding the interaction between these organisms and the host via the elicitor–receptor interaction is essential to equip us with the knowledge necessary to design durable resistance in plants. In addition, it is also important to look into the role played by beneficial microbes and synthetic elicitors in activating plants’ defense and protection against disease and predation. This review addresses receptors, elicitors, and the receptor–elicitor interactions where these components in fungi, bacteria, and insects will be elaborated, giving special emphasis to the molecules, responses, and mechanisms at play, variations between organisms where applicable, and applications and prospects. Full article
(This article belongs to the Special Issue Plant Innate Immunity 3.0)
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Review
Unravelling the Roles of Nitrogen Nutrition in Plant Disease Defences
Int. J. Mol. Sci. 2020, 21(2), 572; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21020572 - 16 Jan 2020
Cited by 23 | Viewed by 2447
Abstract
Nitrogen (N) is one of the most important elements that has a central impact on plant growth and yield. N is also widely involved in plant stress responses, but its roles in host-pathogen interactions are complex as each affects the other. In this [...] Read more.
Nitrogen (N) is one of the most important elements that has a central impact on plant growth and yield. N is also widely involved in plant stress responses, but its roles in host-pathogen interactions are complex as each affects the other. In this review, we summarize the relationship between N nutrition and plant disease and stress its importance for both host and pathogen. From the perspective of the pathogen, we describe how N can affect the pathogen’s infection strategy, whether necrotrophic or biotrophic. N can influence the deployment of virulence factors such as type III secretion systems in bacterial pathogen or contribute nutrients such as gamma-aminobutyric acid to the invader. Considering the host, the association between N nutrition and plant defence is considered in terms of physical, biochemical and genetic mechanisms. Generally, N has negative effects on physical defences and the production of anti-microbial phytoalexins but positive effects on defence-related enzymes and proteins to affect local defence as well as systemic resistance. N nutrition can also influence defence via amino acid metabolism and hormone production to affect downstream defence-related gene expression via transcriptional regulation and nitric oxide (NO) production, which represents a direct link with N. Although the critical role of N nutrition in plant defences is stressed in this review, further work is urgently needed to provide a comprehensive understanding of how opposing virulence and defence mechanisms are influenced by interacting networks. Full article
(This article belongs to the Special Issue Plant Innate Immunity 3.0)
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