scholarly journals A secreted metal-binding protein protects necrotrophic phytopathogens from reactive oxygen species

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Lulu Liu ◽  
Virginie Gueguen-Chaignon ◽  
Isabelle R Gonçalves ◽  
Christine Rascle ◽  
Martine Rigault ◽  
...  
Keyword(s):  
Metal Binding ◽  
Plant Cell Wall ◽  
Metal Accumulation ◽  
Cell Wall Degrading Enzymes ◽  
Dickeya Dadantii ◽  
Phytopathogenic Bacterium ◽  
Gram Positive Bacteria ◽  
Plant Infection ◽  
Ros Formation ◽  
Iron Binding Proteins

Abstract Few secreted proteins involved in plant infection common to necrotrophic bacteria, fungi and oomycetes have been identified except for plant cell wall-degrading enzymes. Here we study a family of iron-binding proteins that is present in Gram-negative and Gram-positive bacteria, fungi, oomycetes and some animals. Homolog proteins in the phytopathogenic bacterium Dickeya dadantii (IbpS) and the fungal necrotroph Botrytis cinerea (BcIbp) are involved in plant infection. IbpS is secreted, can bind iron and copper, and protects the bacteria against H2O2-induced death. Its 1.7 Å crystal structure reveals a classical Venus Fly trap fold that forms dimers in solution and in the crystal. We propose that secreted Ibp proteins binds exogenous metals and thus limit intracellular metal accumulation and ROS formation in the microorganisms.

scholarly journals Inactivation of pecS restores the virulence of mutants devoid of osmoregulated periplasmic glucans in the phytopathogenic bacterium Dickeya dadantii

Microbiology ◽  
2014 ◽  
Vol 160 (4) ◽  
pp. 766-777 ◽  
Author(s):  
Sébastien Bontemps-Gallo ◽  
Edwige Madec ◽  
Jean-Marie Lacroix
Keyword(s):  
Plant Cell Wall ◽  
Transcriptional Regulator ◽  
Soft Rot ◽  
Cellular Functions ◽  
Cell Wall Degrading Enzymes ◽  
Dickeya Dadantii ◽  
Phytopathogenic Bacterium ◽  
Wide Range ◽  
Severe Reduction ◽  
Rot Disease

Dickeya dadantii is a phytopathogenic enterobacterium that causes soft rot disease in a wide range of plant species. Maceration, an apparent symptom of the disease, is the result of the synthesis and secretion of a set of plant cell wall-degrading enzymes (PCWDEs), but many additional factors are required for full virulence. Among these, osmoregulated periplasmic glucans (OPGs) and the PecS transcriptional regulator are essential virulence factors. Several cellular functions are controlled by both OPGs and PecS. Strains devoid of OPGs display a pleiotropic phenotype including total loss of virulence, loss of motility and severe reduction in the synthesis of PCWDEs. PecS is one of the major regulators of virulence in D. dadantii, acting mainly as a repressor of various cellular functions including virulence, motility and synthesis of PCWDEs. The present study shows that inactivation of the pecS gene restored virulence in a D. dadantii strain devoid of OPGs, indicating that PecS cannot be de-repressed in strains devoid of OPGs.

scholarly journals The Xylanase Inhibitor TAXI-I Increases Plant Resistance to Botrytis cinerea by Inhibiting the BcXyn11a Xylanase Necrotizing Activity

Plants ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 601
Author(s):  
Silvio Tundo ◽  
Maria Chiara Paccanaro ◽  
Ibrahim Elmaghraby ◽  
Ilaria Moscetti ◽  
Renato D’Ovidio ◽  
...  
Keyword(s):  
Cell Wall ◽  
Botrytis Cinerea ◽  
Plant Cell Wall ◽  
Wild Type ◽  
Cell Wall Degrading Enzymes ◽  
Targeted Deletion ◽  
Plant Infection ◽  
Transgenic Lines ◽  
Xylanase Inhibitor ◽  
Main Component

During host plant infection, pathogens produce a wide array of cell wall degrading enzymes (CWDEs) to break the plant cell wall. Among CWDEs, xylanases are key enzymes in the degradation of xylan, the main component of hemicellulose. Targeted deletion experiments support the direct involvement of the xylanase BcXyn11a in the pathogenesis of Botrytis cinerea. Since the Triticum aestivum xylanase inhibitor-I (TAXI-I) has been shown to inhibit BcXyn11a, we verified if TAXI-I could be exploited to counteract B. cinerea infections. With this aim, we first produced Nicotiana tabacum plants transiently expressing TAXI-I, observing increased resistance to B. cinerea. Subsequently, we transformed Arabidopsis thaliana to express TAXI-I constitutively, and we obtained three transgenic lines exhibiting a variable amount of TAXI-I. The line with the higher level of TAXI-I showed increased resistance to B. cinerea and the absence of necrotic lesions when infiltrated with BcXyn11a. Finally, in a droplet application experiment on wild-type Arabidopsis leaves, TAXI-I prevented the necrotizing activity of BcXyn11a. These results would confirm that the contribution of BcXyn11a to virulence is due to its necrotizing rather than enzymatic activity. In conclusion, our experiments highlight the ability of the TAXI-I xylanase inhibitor to counteract B. cinerea infection presumably by preventing the necrotizing activity of BcXyn11a.

scholarly journals Genome wide identification of bacterial genes required for plant infection by Tn-seq

2017 ◽  
Author(s):  
Kevin Royet ◽  
Nicolas Parisot ◽  
Agnès Rodrigue ◽  
Erwan Gueguen ◽  
Guy Condemine
Keyword(s):  
Virulence Factors ◽  
Pathogenic Bacteria ◽  
High Throughput Sequencing ◽  
Plant Cell Wall ◽  
Infection Process ◽  
Cell Wall Degrading Enzymes ◽  
Plant Pathogenic Bacteria ◽  
Regulatory Cascade ◽  
Plant Infection ◽  
Genome Wide

ABSTRACTSoft rot enterobacteria (DickeyaandPectobacterium) are major pathogens that cause diseases on plants of agricultural importance such as potato and ornamentals. Long term studies to identify virulence factors of these bacteria focused mostly on plant cell wall degrading enzymes secreted by the type II secretion system and the regulation of their expression. To identify new virulence factors we performed a Tn-seq genome-wide screen of a transposon mutant library during chicory infection followed by high-throughput sequencing. This allowed the detection of mutants with reduced but also increased fitness in the plant. Virulence factors identified differed from those previously known since diffusible ones (secreted enzymes, siderophores or metabolites) were not detected by this screen. In addition to genes encoding proteins of unknown function that could be new virulence factors, others could be assigned to known biological functions. The central role of the FlhDC regulatory cascade in the control of virulence was highlighted with the identification of new members of this pathway. Scarcity of the plant in certain amino acids and nucleic acids required presence of the corresponding biosynthetic genes in the bacteria. Their products could be targets for the development of antibacterial compounds. Among the genes required for full development in chicory we also identified six genes involved in the glycosylation of the flagellin FliC, glycosylation, which in other plant pathogenic bacteria contributes to virulence.Author summaryIdentification of virulence factors of plant pathogenic bacteria has relied on the test of individual mutants on plants, a time-consuming method. New methods like transcriptomic or proteomic can now be used but they only allow the identification of genes induced during the infection process and non-induced genes may be missed. Tn-seq is a very powerful method to identify genes required for bacterial growth in their host. We used for the first time this method in a plant pathogenic bacteria to identify genes required for the multiplication ofDickeya dadantiiin chicory. We identified about 100 genes with decreased or increased fitness in the plant. Most of them had no previously described role in bacterial virulence. We unveiled important metabolic genes and regulators of motility and virulence. We showed thatD. dadantiiflagellin is glycosylated and that this modification confers fitness to the bacteria during plant infection. Our work opens the way to the use of Tn-seq with bacterial phytopathogens. Assay by this method of large collections of environmental pathogenic strains now available will allow an easy and rapid identification of new virulence factors.

scholarly journals Role of the Nucleoid-Associated Protein H-NS in the Synthesis of Virulence Factors in the Phytopathogenic Bacterium Erwinia chrysanthemi

2001 ◽  
Vol 14 (1) ◽  
pp. 10-20 ◽  
Author(s):  
William Nasser ◽  
Michel Faelen ◽  
Nicole Hugouvieux-Cotte-Pattat ◽  
Sylvie Reverchon
Keyword(s):  
Virulence Factors ◽  
Growth Phase ◽  
Reverse Genetics ◽  
Plant Cell Wall ◽  
Pectate Lyase ◽  
Erwinia Chrysanthemi ◽  
Exponential Growth Phase ◽  
Cell Wall Degrading Enzymes ◽  
Phytopathogenic Bacterium ◽  
Flagellar Proteins

The ability of the enterobacterium Erwinia chrysanthemi to induce pathogenesis in plant tissue is strongly related to the massive production of plant-cell-wall-degrading enzymes (pectinases, cellulases, and proteases). Additional factors, including flagellar proteins and exopolysaccharides (EPS), also are required for the efficient colonization of plants. Production of these virulence factors, particularly pectate lyases, the main virulence determinant, is tightly regulated by environmental conditions. The possible involvement of the protein H-NS in this process was investigated. The E. chrysanthemi hns gene was cloned by complementation of an Escherichia coli hns mutation. Its nucleotide sequence contains a 405-bp open reading frame that codes for a protein with 85% identity to the E. coli H-NS protein. An E. chrysanthemi hns mutant was constructed by reverse genetics. This mutant displays a reduced growth rate and motility but an increased EPS synthesis and sensitivity toward high osmolarity. Furthermore, pectate lyase production is dramatically reduced in this mutant. The hns mutation acts on at least two conditions affecting pectate lyase synthesis: induction of pectate lyase synthesis at low temperatures (25°C) is no longer observed in the hns mutant and induction of pectate lyase production occurs in the late stationary growth phase in the hns background, instead of in the late exponential growth phase as it does in the parental strain. Moreover, the E. chrysanthemi hns mutant displays reduced virulence on plants. Taken together, these data suggest that H-NS plays a crucial role in the expression of the virulence genes and in the pathogenicity of E. chrysanthemi.

scholarly journals Mapping the complex transcriptional landscape of the phytopathogenic bacterium Dickeya dadantii

2020 ◽  
Author(s):  
Raphaël Forquet ◽  
Xuejiao Jiang ◽  
William Nasser ◽  
Florence Hommais ◽  
Sylvie Reverchon ◽  
...  
Keyword(s):  
Gene Expression ◽  
Environmental Changes ◽  
Computational Method ◽  
Fine Tuning ◽  
Transcription Start ◽  
Dickeya Dadantii ◽  
Phytopathogenic Bacterium ◽  
Plant Infection ◽  
Wide Range ◽  
Variable Gene

AbstractDickeya dadantii is a phytopathogenic bacterium that causes soft rot in a wide range of plant hosts worldwide and a model organism for studying gene regulation during the pathogenic process. The present study provides a comprehensive and annotated transcriptomic map of D. dadantii obtained by a computational method combining three independent transcriptomic datasets covering a wide range of conditions which closely reproduce the variations of transcription occurring in the course of plant infection: (1) paired-end RNA-seq data for a precise reconstruction of the RNA landscape, (2) DNA microarray data reflecting gene response to sudden environmental shocks mimicking conditions encountered by bacteria in the plant, (3) dRNA-seq data for a specific high-resolution mapping of transcription start sites. We define transcription units throughout the genome, and map the associated transcription start and termination sites with a quantitative magnitude analysis. Our results show that transcription units sometimes coincide with predicted operons but are generally longer, most of them exhibiting internal promoters and terminators that generate alternative transcripts of variable gene composition. We characterize the occurrence of transcriptional read-through at terminators, which might play a basal regulation role and explain the extent of transcription beyond the scale of operons. We finally highlight the presence of noncontiguous operons and excludons in D. dadantii genome, novel genomic arrangements that might contribute to the basal coordination of transcription. The highlighted transcriptional organization may allow D. dadantii finely adjusting its gene expression program for a rapid adaptation to fast changing environment relevant to plant infection.ImportanceThis is the first transcriptomic map of a phytopathogen, characterized under physiological conditions encountered by the bacteria during the infection process. It might therefore significantly contribute to further progress in the field of phytopathogenicity. Our findings also provide insights into basal rules of coordination of transcription that might be valid for other bacteria, and may raise interest in the field of microbiology in general. In particular, we demonstrate that gene expression is coordinated at the scale of transcription units rather than operons, which are larger functional genomic units capable of generating transcripts with variable gene composition for a fine-tuning of gene expression in response to environmental changes. In line with recent studies, our findings indicate that the canonical operon model is insufficient to explain the complexity of bacterial transcriptomes.

scholarly journals The Phytopathogen Dickeya dadantii (Erwinia chrysanthemi 3937) Is a Pathogen of the Pea Aphid

2006 ◽  
Vol 72 (3) ◽  
pp. 1956-1965 ◽  
Author(s):  
Anne-Marie Grenier ◽  
Gabrielle Duport ◽  
Sylvie Pagès ◽  
Guy Condemine ◽  
Yvan Rahbé
Keyword(s):  
Acyrthosiphon Pisum ◽  
Ecological Impact ◽  
Sitophilus Oryzae ◽  
Pea Aphid ◽  
Erwinia Chrysanthemi ◽  
Future Research ◽  
Close Relative ◽  
Bacterial Cells ◽  
Dickeya Dadantii ◽  
Phytopathogenic Bacterium

ABSTRACT Dickeya dadantii (Erwinia chrysanthemi) is a phytopathogenic bacterium causing soft rot diseases on many crops. The sequencing of its genome identified four genes encoding homologues of the Cyt family of insecticidal toxins from Bacillus thuringiensis, which are not present in the close relative Pectobacterium carotovorum subsp. atrosepticum. The pathogenicity of D. dadantii was tested on the pea aphid Acyrthosiphon pisum, and the bacterium was shown to be highly virulent for this insect, either by septic injury or by oral infection. The lethal inoculum dose was calculated to be as low as 10 ingested bacterial cells. A D. dadantii mutant with the four cytotoxin genes deleted showed a reduced per os virulence for A. pisum, highlighting the potential role of at least one of these genes in pathogenicity. Since only one bacterial pathogen of aphids has been previously described (Erwinia aphidicola), other species from the same bacterial group were tested. The pathogenic trait for aphids was shown to be widespread, albeit variable, within the phytopathogens, with no link to phylogenetic positioning in the Enterobacteriaceae. Previously characterized gut symbionts from thrips (Erwinia/Pantoea group) were also highly pathogenic to the aphid, whereas the potent entomopathogen Photorhabdus luminescens was not. D. dadantii is not a generalist insect pathogen, since it has low pathogenicity for three other insect species (Drosophila melanogaster, Sitophilus oryzae, and Spodoptera littoralis). D. dadantii was one of the most virulent aphid pathogens in our screening, and it was active on most aphid instars, except for the first one, probably due to anatomical filtering. The observed difference in virulence toward apterous and winged aphids may have an ecological impact, and this deserves specific attention in future research.

scholarly journals Synergistic Effect of Different Plant Cell Wall–Degrading Enzymes Is Important for Virulence of Fusarium graminearum

2017 ◽  
Vol 30 (11) ◽  
pp. 886-895 ◽  
Author(s):  
Maria Chiara Paccanaro ◽  
Luca Sella ◽  
Carla Castiglioni ◽  
Francesca Giacomello ◽  
Ana Lilia Martínez-Rocha ◽  
...  
Keyword(s):  
Cell Wall ◽  
Fusarium Graminearum ◽  
Plant Cell ◽  
Plant Cell Wall ◽  
Xylanase Activity ◽  
Cellulase Activity ◽  
Wild Type ◽  
Cell Wall Degrading Enzymes ◽  
Xylanase Production ◽  
Significant Difference

Endo-polygalacturonases (PGs) and xylanases have been shown to play an important role during pathogenesis of some fungal pathogens of dicot plants, while their role in monocot pathogens is less defined. Pg1 and xyr1 genes of the wheat pathogen Fusarium graminearum encode the main PG and the major regulator of xylanase production, respectively. Single- and double-disrupted mutants for these genes were obtained to assess their contribution to fungal infection. Compared with wild-type strain, the ∆pg mutant showed a nearly abolished PG activity, slight reduced virulence on soybean seedlings, but no significant difference in disease symptoms on wheat spikes; the ∆xyr mutant was strongly reduced in xylanase activity and moderately reduced in cellulase activity but was as virulent as wild type on both soybean and wheat plants. Consequently, the ΔpgΔxyr double mutant was impaired in xylanase, PG, and cellulase activities but, differently from single mutants, was significantly reduced in virulence on both plants. These findings demonstrate that the concurrent presence of PG, xylanase, and cellulase activities is necessary for full virulence. The observation that the uronides released from wheat cell wall after a F. graminearum PG treatment were largely increased by the fungal xylanases suggests that these enzymes act synergistically in deconstructing the plant cell wall.

scholarly journals Virulence Genes of the Phytopathogen Rhodococcus fascians Show Specific Spatial and Temporal Expression Patterns During Plant Infection

2002 ◽  
Vol 15 (4) ◽  
pp. 398-403 ◽  
Author(s):  
Karen Cornelis ◽  
Tania Maes ◽  
Mondher Jaziri ◽  
Marcelle Holsters ◽  
Koen Goethals
Keyword(s):  
Virulence Genes ◽  
Expression Profiles ◽  
Bacterial Colonization ◽  
Expression Patterns ◽  
Shoot Meristem ◽  
Plant Surface ◽  
Phytopathogenic Bacterium ◽  
Plant Parts ◽  
Plant Infection ◽  
Rhodococcus Fascians

The phytopathogenic bacterium Rhodococcus fascians provokes shoot meristem formation and malformations on aerial plant parts, mainly at the axils. The interaction is accompanied by bacterial colonization of the plant surface and tissues. Upon infection, the two bacterial loci required for full virulence, fas and att, were expressed only at the sites of symptom development, although their expression profiles differed both spatially and temporally. The att locus was expressed principally in bacteria located on the plant surface at early stages of infection. Expression of the fas locus occurred throughout infection, mainly in bacteria that were penetrating, or had penetrated, the plant tissues and coincided with sites of meristem initiation and proliferation. The implications for the regulation of virulence genes of R. fascians during plant infection are discussed.

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