scholarly journals The Flower-Infecting Fungus Ustilaginoidea virens Subverts Plant Immunity by Secreting a Chitin-Binding Protein

2021 ◽  
Vol 12 ◽  
Author(s):  
Guo-Bang Li ◽  
Jing Fan ◽  
Jin-Long Wu ◽  
Jia-Xue He ◽  
Jie Liu ◽  
...  
Keyword(s):  
Induced Defense ◽  
Plant Immunity ◽  
Floral Organ ◽  
Defense Responses ◽  
High Yield ◽  
In Planta ◽  
Callose Deposition ◽  
Ustilaginoidea Virens ◽  
Chitin Binding Protein

Ustilaginoidea virens is a biotrophic fungal pathogen specifically colonizing rice floral organ and causes false smut disease of rice. This disease has emerged as a serious problem that hinders the application of high-yield rice cultivars, by reducing grain yield and quality as well as introducing mycotoxins. However, the pathogenic mechanisms of U. virens are still enigmatic. Here we demonstrate that U. virens employs a secreted protein UvCBP1 to manipulate plant immunity. In planta expression of UvCBP1 led to compromised chitin-induced defense responses in Arabidopsis and rice, including burst of reactive oxygen species (ROS), callose deposition, and expression of defense-related genes. In vitro-purified UvCBP1 protein competes with rice chitin receptor OsCEBiP to bind to free chitin, thus impairing chitin-triggered rice immunity. Moreover, UvCBP1 could significantly promote infection of U. virens in rice flowers. Our results uncover a mechanism of a floral fungus suppressing plant immunity and pinpoint a universal role of chitin-battlefield during plant–fungi interactions.

scholarly journals The Effectiveness of Induced Defense Responses in a Susceptible Potato Genotype Depends on the Growth Rate of Phytophthora infestans

2019 ◽  
Vol 32 (1) ◽  
pp. 76-85 ◽  
Author(s):  
Cécile Thomas ◽  
Romain Mabon ◽  
Didier Andrivon ◽  
Florence Val
Keyword(s):  
Growth Rate ◽  
Late Blight ◽  
Phytophthora Infestans ◽  
Induced Defense ◽  
Plant Immunity ◽  
Defense Responses ◽  
Alternative Methods ◽  
Gene Expressions

Phytophthora infestans causes the devastating potato late blight disease, which is widely controlled with fungicides. However, the debate about chemical control is fueling a promotion toward alternative methods. In this context, the enhancement of natural plant immunity could be a strategy for more sustainable protection. We previously demonstrated that a concentrated culture filtrate (CCF) of P. infestans primes defense reactions in potato. They are genotype-dependent and metabolites produced decrease pathogen growth in vitro but not in vivo on tubers. Induced potato defenses are assumed to affect P. infestans life history traits depending on strains. This assumption was studied in vivo through induced leaflets on a susceptible genotype inoculated with four P. infestans strains differing for lesion growth rate. This study combines both defenses mechanistic analysis and ecological observations. Defense-gene expressions were thus assessed by quantitative reverse transcription-polymerase chain reaction; pathogen development was simultaneously evaluated by measuring necrosis, quantifying mycelial DNA, and counting sporangia. The results showed that CCF pretreatment reduced the pathogenicity differences between slow- and fast-growing strains. Moreover, after elicitation, PR-1, PR-4, PAL, POX, and THT induction was strain-dependent. These results suggest that P. infestans could develop different strategies to overcome plant defenses and should be considered in biocontrol and epidemic management of late blight.

scholarly journals DspA/E, a Type III Effector Essential for Erwinia amylovora Pathogenicity and Growth In Planta, Induces Cell Death in Host Apple and Nonhost Tobacco Plants

2006 ◽  
Vol 19 (1) ◽  
pp. 16-24 ◽  
Author(s):  
Tristan Boureau ◽  
Hayat ElMaarouf-Bouteau ◽  
Amélie Garnier ◽  
Marie-Noëlle Brisset ◽  
Claude Perino ◽  
...  
Keyword(s):  
Cell Death ◽  
Type Iii Secretion ◽  
Erwinia Amylovora ◽  
Marker Gene ◽  
Defense Responses ◽  
In Planta ◽  
Callose Deposition ◽  
Type Iii Effector ◽  
Type Iii

Erwinia amylovora is responsible for fire blight, a necrotic disease of apples and pears. E. amylovora relies on a type III secretion system (TTSS) to induce disease on hosts and hypersensitive response (HR) on nonhost plants. The DspA/E protein is essential for E. amylovora pathogenicity and is secreted via the TTSS in vitro. DspA/E belongs to a type III effector family that is conserved in several phytopathogenic bacteria. In E. amylovora, DspA/E has been implicated in the generation of an oxidative stress during disease and the suppression of callose deposition. We investigated the fate of DspA/E in planta. DspA/E delivered artificially to apple or tobacco cells by agroinfection induced necrotic symptoms, indicating that DspA/E was probably injected via the TTSS. We confirmed that DspA/E acts as a major cell-death inducer during disease and HR, because the dspA/E mutant is severely impaired in its ability to induce electrolyte leakage in apple and tobacco leaves. Expression of the defense marker gene PR1 was delayed when dspA/E was transiently expressed in tobacco, suggesting that DspA/E-mediated necrosis may be associated with an alteration of defense responses.

scholarly journals A peroxisomal β-oxidative pathway contributes to the formation of C6–C1 aromatic volatiles in poplar

2021 ◽  
Author(s):  
Nathalie D Lackus ◽  
Axel Schmidt ◽  
Jonathan Gershenzon ◽  
Tobias G Köllner
Keyword(s):  
Cinnamic Acid ◽  
Aromatic Compounds ◽  
Populus Trichocarpa ◽  
Alternative Pathway ◽  
Gene Families ◽  
Defense Responses ◽  
In Planta ◽  
Black Cottonwood ◽  
Oxidative Pathway

AbstractBenzenoids (C6–C1 aromatic compounds) play important roles in plant defense and are often produced upon herbivory. Black cottonwood (Populus trichocarpa) produces a variety of volatile and nonvolatile benzenoids involved in various defense responses. However, their biosynthesis in poplar is mainly unresolved. We showed feeding of the poplar leaf beetle (Chrysomela populi) on P. trichocarpa leaves led to increased emission of the benzenoid volatiles benzaldehyde, benzylalcohol, and benzyl benzoate. The accumulation of salicinoids, a group of nonvolatile phenolic defense glycosides composed in part of benzenoid units, was hardly affected by beetle herbivory. In planta labeling experiments revealed that volatile and nonvolatile poplar benzenoids are produced from cinnamic acid (C6–C3). The biosynthesis of C6–C1 aromatic compounds from cinnamic acid has been described in petunia (Petunia hybrida) flowers where the pathway includes a peroxisomal-localized chain shortening sequence, involving cinnamate-CoA ligase (CNL), cinnamoyl-CoA hydratase/dehydrogenase (CHD), and 3-ketoacyl-CoA thiolase (KAT). Sequence and phylogenetic analysis enabled the identification of small CNL, CHD, and KAT gene families in P. trichocarpa. Heterologous expression of the candidate genes in Escherichia coli and characterization of purified proteins in vitro revealed enzymatic activities similar to those described in petunia flowers. RNA interference-mediated knockdown of the CNL subfamily in gray poplar (Populus x canescens) resulted in decreased emission of C6–C1 aromatic volatiles upon herbivory, while constitutively accumulating salicinoids were not affected. This indicates the peroxisomal β-oxidative pathway participates in the formation of volatile benzenoids. The chain shortening steps for salicinoids, however, likely employ an alternative pathway.

scholarly journals Xanthan Pyruvilation Is Essential for the Virulence of Xanthomonas campestris pv. campestris

2016 ◽  
Vol 29 (9) ◽  
pp. 688-699 ◽  
Author(s):  
María Isabel Bianco ◽  
Laila Toum ◽  
Pablo Marcelo Yaryura ◽  
Natalia Mielnichuk ◽  
Gustavo Eduardo Gudesblat ◽  
...  
Keyword(s):  
Xanthomonas Campestris ◽  
Defense Responses ◽  
Plant Defense Responses ◽  
In Planta ◽  
Callose Deposition ◽  
Disease Symptoms ◽  
The Relationship ◽  
Plant Surfaces ◽  
Xanthomonas Campestris Pv Campestris ◽  
Successful Colonization

Xanthan, the main exopolysaccharide (EPS) synthesized by Xanthomonas spp., contributes to bacterial stress tolerance and enhances attachment to plant surfaces by helping in biofilm formation. Therefore, xanthan is essential for successful colonization and growth in planta and has also been proposed to be involved in the promotion of pathogenesis by calcium ion chelation and, hence, in the suppression of the plant defense responses in which this cation acts as a signal. The aim of this work was to study the relationship between xanthan structure and its role as a virulence factor. We analyzed four Xanthomonas campestris pv. campestris mutants that synthesize structural variants of xanthan. We found that the lack of acetyl groups that decorate the internal mannose residues, ketal-pyruvate groups, and external mannose residues affects bacterial adhesion and biofilm architecture. In addition, the mutants that synthesized EPS without pyruvilation or without the external mannose residues did not develop disease symptoms in Arabidopsis thaliana. We also observed that the presence of the external mannose residues and, hence, pyruvilation is required for xanthan to suppress callose deposition as well as to interfere with stomatal defense. In conclusion, pyruvilation of xanthan seems to be essential for Xanthomonas campestris pv. campestris virulence.

scholarly journals The flavin monooxygenase Bs3 triggers cell death in plants, impairs growth in yeast and produces H2O2 in vitro

PLoS ONE ◽  
2021 ◽  
Vol 16 (8) ◽  
pp. e0256217
Author(s):  
Christina Krönauer ◽  
Thomas Lahaye
Keyword(s):  
Nadph Oxidase ◽  
Oxidation State ◽  
Transcriptional Activation ◽  
Oxidase Activity ◽  
Plant Immunity ◽  
Striking Similarity ◽  
In Planta ◽  
Nadph Oxidase Activity ◽  
Wide Range

The pepper resistance gene Bs3 triggers a hypersensitive response (HR) upon transcriptional activation by the corresponding effector protein AvrBs3 from the bacterial pathogen Xanthomonas. Expression of Bs3 in yeast inhibited proliferation, demonstrating that Bs3 function is not restricted to the plant kingdom. The Bs3 sequence shows striking similarity to flavin monooxygenases (FMOs), an FAD- and NADPH-containing enzyme class that is known for the oxygenation of a wide range of substrates and their potential to produce H2O2. Since H2O2 is a hallmark metabolite in plant immunity, we analyzed the role of H2O2 during Bs3 HR. We purified recombinant Bs3 protein from E. coli and confirmed the FMO function of Bs3 with FAD binding and NADPH oxidase activity in vitro. Translational fusion of Bs3 to the redox reporter roGFP2 indicated that the Bs3-dependent HR induces an increase of the intracellular oxidation state in planta. To test if the NADPH oxidation and putative H2O2 production of Bs3 is sufficient to induce HR, we adapted previous studies which have uncovered mutations in the NADPH binding site of FMOs that result in higher NADPH oxidase activity. In vitro studies demonstrated that recombinant Bs3S211A protein has twofold higher NADPH oxidase activity than wildtype Bs3. Translational fusions to roGFP2 showed that Bs3S211A also increased the intracellular oxidation state in planta. Interestingly, while the mutant derivative Bs3S211A had an increase in NADPH oxidase capacity, it did not trigger HR in planta, ultimately revealing that H2O2 produced by Bs3 on its own is not sufficient to trigger HR.

AtCERK1 Phosphorylation Site S493 Contributes to the Transphosphorylation of Downstream Components for Chitin-Induced Immune Signaling

2019 ◽  
Vol 60 (8) ◽  
pp. 1804-1810 ◽  
Author(s):  
Maruya Suzuki ◽  
Issei Yoshida ◽  
Kenkichi Suto ◽  
Yoshitake Desaki ◽  
Naoto Shibuya ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Induced Defense ◽  
Phosphorylation Site ◽  
Defense Responses ◽  
Kinase Domain ◽  
Kinase Assay ◽  
Structural Basis ◽  
Downstream Signaling ◽  
Signaling Components

Abstract While ligand-induced autophosphorylation of receptor-like kinases (RLKs) is known to be critical for triggering the downstream responses, biochemical mechanism by which each phosphorylation site contributes to the initiation of corresponding signaling cascades is only poorly understood, except the involvement of some phosphorylation sites in the regulation of catalytic activity of these RLKs. In this article, we first confirmed that the phosphorylation of S493 of AtCERK1 is involved in the regulation of chitin-induced defense responses by the complementation of an atcerk1 mutant with AtCERK1(S493A) cDNA. In vitro kinase assay with the heterologously expressed kinase domain of AtCERK1, GST-AtCERK1cyt, showed that the S493A mutation did not affect the autophosphorylation of AtCERK1 itself but diminished the transphosphorylation of downstream signaling components, PBL27 and PUB4. On the other hand, a phosphomimetic mutant, GST-AtCERK1(S493D)cyt, transphosphorylated these substrates as similar to the wild type AtCERK1. These results suggested that the phosphorylation of S493 does not contribute to the regulation of catalytic activity but plays an important role for the transphosphorylation of the downstream signaling components, thus contributing to the initiation of chitin signaling. To our knowledge, it is a novel finding that a specific phosphorylation site contributes to the regulation of transphosphorylation activity of RLKs. Further studies on the structural basis by which S493 phosphorylation contributes to the regulation of transphosphorylation would contribute to the understanding how the ligand-induced autophosphorylation of RLKs properly regulates the downstream signaling.

scholarly journals Jasmonic Acid at the Crossroads of Plant Immunity and Pseudomonas syringae Virulence

2020 ◽  
Vol 21 (20) ◽  
pp. 7482
Author(s):  
Aarti Gupta ◽  
Mamta Bhardwaj ◽  
Lam-Son Phan Tran
Keyword(s):  
Jasmonic Acid ◽  
Plant Defense ◽  
Pseudomonas Syringae ◽  
Regulatory Networks ◽  
Genetic Manipulation ◽  
Plant Immunity ◽  
Stomatal Closure ◽  
Defense Responses ◽  
Plant Defense Responses ◽  
Callose Deposition

Sensing of pathogen infection by plants elicits early signals that are transduced to affect defense mechanisms, such as effective blockage of pathogen entry by regulation of stomatal closure, cuticle, or callose deposition, change in water potential, and resource acquisition among many others. Pathogens, on the other hand, interfere with plant physiology and protein functioning to counteract plant defense responses. In plants, hormonal homeostasis and signaling are tightly regulated; thus, the phytohormones are qualified as a major group of signaling molecules controlling the most widely tinkered regulatory networks of defense and counter-defense strategies. Notably, the phytohormone jasmonic acid mediates plant defense responses to a wide array of pathogens. In this review, we present the synopsis on the jasmonic acid metabolism and signaling, and the regulatory roles of this hormone in plant defense against the hemibiotrophic bacterial pathogen Pseudomonas syringae. We also elaborate on how this pathogen releases virulence factors and effectors to gain control over plant jasmonic acid signaling to effectively cause disease. The findings discussed in this review may lead to ideas for the development of crop cultivars with enhanced disease resistance by genetic manipulation.

scholarly journals A Role of Cytokinin Transporter in Arabidopsis Immunity

2017 ◽  
Vol 30 (4) ◽  
pp. 325-333 ◽  
Author(s):  
Shuai Wang ◽  
Shu Wang ◽  
Qi Sun ◽  
Leiyun Yang ◽  
Ying Zhu ◽  
...  
Keyword(s):  
Disease Resistance ◽  
Induced Defense ◽  
Plant Immunity ◽  
Receptor Gene ◽  
Defense Responses ◽  
Plant Growth And Development ◽  
Immune Receptor ◽  
Receptor Mutant ◽  
Induced Defense Responses

The phytohormone cytokinin (CK) is not only essential for plant growth and development but also impacts plant immunity. A mutant screen in a constitutively active plant immune receptor mutant snc1 (suppressor of npr1, constitutive1) identified a suppressor mutation of SNC1-induced defense responses in an ABC transporter coding gene ABCG14. ABCG14 transports CK from roots to the shoots, and the suppression of the SNC1-mediated defense response by the loss of ABCG14 is due to a deficiency of trans-zeatin (tZ)-type CK in the shoot. In addition, exogenous application of the tZ-type CK enhances disease resistance associated with increased expression of the plant immune receptor gene SNC1. Taken together, this study further established the role of tZ-type CK in disease resistance and suggests a new intersection of CKs with plant immunity at the expression regulation of a plant immune receptor gene.

scholarly journals Role of Benzoic Acid and Lettucenin A in the Defense Response of Lettuce against Soil-Borne Pathogens

Plants ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 2336
Author(s):  
Saskia Windisch ◽  
Anja Walter ◽  
Narges Moradtalab ◽  
Frank Walker ◽  
Birgit Höglinger ◽  
...  
Keyword(s):  
Benzoic Acid ◽  
Defense Mechanism ◽  
Induced Defense ◽  
Hyphal Growth ◽  
Defense Responses ◽  
Soil Culture ◽  
Defense Compounds ◽  
Soil Borne Pathogens ◽  
Induced Defense Responses

Soil-borne pathogens can severely limit plant productivity. Induced defense responses are plant strategies to counteract pathogen-related damage and yield loss. In this study, we hypothesized that benzoic acid and lettucenin A are involved as defense compounds against Rhizoctonia solani and Olpidium virulentus in lettuce. To address this hypothesis, we conducted growth chamber experiments using hydroponics, peat culture substrate and soil culture in pots and minirhizotrons. Benzoic acid was identified as root exudate released from lettuce plants upon pathogen infection, with pre-accumulation of benzoic acid esters in the root tissue. The amounts were sufficient to inhibit hyphal growth of R. solani in vitro (30%), to mitigate growth retardation (51%) and damage of fine roots (130%) in lettuce plants caused by R. solani, but were not able to overcome plant growth suppression induced by Olpidium infection. Additionally, lettucenin A was identified as major phytoalexin, with local accumulation in affected plant tissues upon infection with pathogens or chemical elicitation (CuSO4) and detected in trace amounts in root exudates. The results suggest a two-stage defense mechanism with pathogen-induced benzoic acid exudation initially located in the rhizosphere followed by accumulation of lettucenin A locally restricted to affected root and leaf tissues.

scholarly journals The PTI to ETI Continuum in Phytophthora-Plant Interactions

2020 ◽  
Vol 11 ◽  
Author(s):  
Zunaira Afzal Naveed ◽  
Xiangying Wei ◽  
Jianjun Chen ◽  
Hira Mubeen ◽  
Gul Shad Ali
Keyword(s):  
Host Defense ◽  
Induced Defense ◽  
Plant Immunity ◽  
Defense Responses ◽  
Mapk Signaling ◽  
Cell Trafficking ◽  
Plant Interactions ◽  
Physiological Processes ◽  
Effector Triggered Immunity ◽  
Induced Defense Responses

Phytophthora species are notorious pathogens of several economically important crop plants. Several general elicitors, commonly referred to as Pathogen-Associated Molecular Patterns (PAMPs), from Phytophthora spp. have been identified that are recognized by the plant receptors to trigger induced defense responses in a process termed PAMP-triggered Immunity (PTI). Adapted Phytophthora pathogens have evolved multiple strategies to evade PTI. They can either modify or suppress their elicitors to avoid recognition by host and modulate host defense responses by deploying hundreds of effectors, which suppress host defense and physiological processes by modulating components involved in calcium and MAPK signaling, alternative splicing, RNA interference, vesicle trafficking, cell-to-cell trafficking, proteolysis and phytohormone signaling pathways. In incompatible interactions, resistant host plants perceive effector-induced modulations through resistance proteins and activate downstream components of defense responses in a quicker and more robust manner called effector-triggered-immunity (ETI). When pathogens overcome PTI—usually through effectors in the absence of R proteins—effectors-triggered susceptibility (ETS) ensues. Qualitatively, many of the downstream defense responses overlap between PTI and ETI. In general, these multiple phases of Phytophthora-plant interactions follow the PTI-ETS-ETI paradigm, initially proposed in the zigzag model of plant immunity. However, based on several examples, in Phytophthora-plant interactions, boundaries between these phases are not distinct but are rather blended pointing to a PTI-ETI continuum.

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