The DinJ/RelE Toxin-Antitoxin System Suppresses Bacterial Proliferation and Virulence of Xylella fastidiosa in Grapevine

Xylella fastidiosa, the causal agent of Pierce’s disease of grapes, is a slow-growing, xylem-limited, bacterial pathogen. Disease progression is characterized by systemic spread of the bacterium through xylem vessel networks, causing leaf-scorching symptoms, senescence, and vine decline. It appears to be advantageous to this pathogen to avoid excessive blockage of xylem vessels, because living bacterial cells are generally found in plant tissue with low bacterial cell density and minimal scorching symptoms. The DinJ/RelE toxin-antitoxin system is characterized here for a role in controlling bacterial proliferation and population size during plant colonization. The DinJ/RelE locus is transcribed from two separate promoters, allowing for coexpression of antitoxin DinJ with endoribonuclease toxin RelE, in addition to independent expression of RelE. The ratio of antitoxin/toxin expressed is dependent on bacterial growth conditions, with lower amounts of antitoxin present under conditions designed to mimic grapevine xylem sap. A knockout mutant of DinJ/RelE exhibits a hypervirulent phenotype, with higher bacterial populations and increased symptom development and plant decline. It is likely that DinJ/RelE acts to prevent excessive population growth, contributing to the ability of the pathogen to spread systemically without completely blocking the xylem vessels and increasing probability of acquisition by the insect vector.

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First Report of Xylella fastidiosa on Catharanthus roseus in Brazil

Plant Disease ◽

10.1094/pdis.1998.82.6.712a ◽

1998 ◽

Vol 82 (6) ◽

pp. 712-712 ◽

Cited By ~ 2

Author(s):

B. Ueno ◽

C. K. Funada ◽

M. A. Yorinori ◽

R. P. Leite

Keyword(s):

Catharanthus Roseus ◽

Xylella Fastidiosa ◽

Xylem Sap ◽

Glass Slide ◽

Bacterial Cells ◽

First Report ◽

Vein Clearing ◽

The Media ◽

Agar Media ◽

The U.S

In 1998, plants of periwinkle (Catharanthus roseus L.) showing small leaves, short internodes, and dieback symptoms were observed in a garden at the Instituto Agronomico do Parana (IAPAR), Londrina, PR, Brazil. Stems of these plants were cut into short sections and the sap extracted from the tissue by squeezing with pliers. The sap was blotted onto a glass slide and examined for the presence of bacteria by light microscopy (×400). Microscopy observations revealed the presence of a large number of slender, rod-shaped bacterial cells. The bacteria present in the stems of periwinkle were isolated on buffered cysteine-yeast extract (BCYE) and periwinkle wilt (PW) agar media. Stems were disinfected in 70% alcohol and cut into short sections, and the sap extracted as described above. The sap was blotted directly onto the media and the plates were incubated at 28°C. Typical colonies of Xylella fastidiosa were observed 10 days after isolation on both media. Indirect immunofluorescence tests with antibody specific to X. fastidiosa and anti-IgG conjugated with tetrametylrhodamine isothiocyanate (TRITC) were carried out with xylem sap of periwinkle stem and the isolated bacteria. In both cases, immunofluorescence tests were positive for X. fastidiosa. These results confirm that periwinkle plants were infected with X. fastidiosa. This is the first report of the association of X. fastidiosa with periwinkle plants in Brazil. However, the symptoms observed for the X. fastidiosa-infected periwinkle plants differed from those described previously in the U.S. (1): those symptoms consisted of marginal chlorosis and occasional vein clearing of leaves and wilting of the plants. Reference: (1) R. E. McCoy et al. Plant Dis. Rep. 62:1022, 1978.

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Zinc Detoxification Is Required for Full Virulence and Modification of the Host Leaf Ionome by Xylella fastidiosa

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-07-14-0221-r ◽

2015 ◽

Vol 28 (4) ◽

pp. 497-507 ◽

Cited By ~ 17

Author(s):

Fernando Navarrete ◽

Leonardo De La Fuente

Keyword(s):

Xylella Fastidiosa ◽

Xylem Sap ◽

Essential Element ◽

Trace Element Composition ◽

Mineral Nutrient ◽

Knockout Mutant ◽

Bacterial Populations ◽

Zn Homeostasis ◽

Increased Sensitivity ◽

High Concentrations

Zinc (Zn) is an essential element for all forms of life because it is a structural or catalytic cofactor of many proteins, but it can have toxic effects at high concentrations; thus, microorganisms must tightly regulate its levels. Here, we evaluated the role of Zn homeostasis proteins in the virulence of the xylem-limited bacterium Xylella fastidiosa, causal agent of Pierce’s disease of grapevine, among other diseases. Two mutants of X. fastidiosa ‘Temecula’ affected in genes which regulate Zn homeostasis (zur) and Zn detoxification (czcD) were constructed. Both knockouts showed increased sensitivity to Zn at physiologically relevant concentrations and increased intracellular accumulation of this metal compared with the wild type. Increased Zn sensitivity was correlated with decreased growth in grapevine xylem sap, reduced twitching motility, and downregulation of exopolysaccharide biosynthetic genes. Tobacco plants inoculated with either knockout mutant showed reduced foliar symptoms and a much reduced (czcD) or absent (zur) modification of the leaf ionome (i.e., the mineral nutrient and trace element composition), as well as reduced bacterial populations. The results show that detoxification of Zn is crucial for the virulence of X. fastidiosa and verifies our previous findings that modification of the host leaf ionome correlates with bacterial virulence.

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Aphrophoridae Role in Xylella fastidiosa subsp. pauca ST53 Invasion in Southern Italy

Pathogens ◽

10.3390/pathogens10081035 ◽

2021 ◽

Vol 10 (8) ◽

pp. 1035

Author(s):

Ugo Picciotti ◽

Nada Lahbib ◽

Valdete Sefa ◽

Francesco Porcelli ◽

Francesca Garganese

Keyword(s):

Pest Management ◽

Plant Pathogen ◽

Southern Italy ◽

Xylella Fastidiosa ◽

Xylem Sap ◽

Disease Spread ◽

Insect Vector ◽

Transmission Control ◽

Olive Quick Decline Syndrome ◽

Olive Trees

The Philaenus spumarius L. (Hemiptera Aphrophoridae) is a xylem-sap feeder vector that acquires Xylella fastidiosa subsp. pauca ST53 during feeding on infected plants. The bacterium is the plant pathogen responsible for olive quick decline syndrome that has decimated olive trees in Southern Italy. Damage originates mainly from the insect vector attitude that multiplies the pathogen potentialities propagating Xf in time and space. The principal action to manage insect-borne pathogens and to contain the disease spread consists in vector and transmission control. The analysis of an innovative and sustainable integrated pest management quantitative strategy that targets the vector and the infection by combining chemical and physical control means demonstrates that it is possible to stop the Xylella invasion. This review updates the available topics addressing vectors’ identification, bionomics, infection management, and induced disease by Xylella invasion to discuss major available tools to mitigate the damage consequent to the disease.

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Lessons from One Fastidious Bacterium to Another: What Can We Learn about Liberibacter Species from Xylella fastidiosa

Insects ◽

10.3390/insects10090300 ◽

2019 ◽

Vol 10 (9) ◽

pp. 300 ◽

Cited By ~ 1

Author(s):

Angela Kruse ◽

Laura A. Fleites ◽

Michelle Heck

Keyword(s):

Control Strategies ◽

Xylella Fastidiosa ◽

Historical Context ◽

Control Plant ◽

Bacterial Pathogen ◽

Pathogen Transmission ◽

Control Measures ◽

Insect Vector ◽

Potential Applicability ◽

Candidatus Liberibacter

Huanglongbing is causing economic devastation to the citrus industry in Florida, and threatens the industry everywhere the bacterial pathogens in the Candidatus Liberibacter genus and their insect vectors are found. Bacteria in the genus cannot be cultured and no durable strategy is available for growers to control plant infection or pathogen transmission. However, scientists and grape growers were once in a comparable situation after the emergence of Pierce’s disease, which is caused by Xylella fastidiosa and spread by its hemipteran insect vector. Proactive quarantine and vector control measures coupled with interdisciplinary data-driven science established control of this devastating disease and pushed the frontiers of knowledge in the plant pathology and vector biology fields. Our review highlights the successful strategies used to understand and control X. fastidiosa and their potential applicability to the liberibacters associated with citrus greening, with a focus on the interactions between bacterial pathogen and insect vector. By placing the study of Candidatus Liberibacter spp. within the current and historical context of another fastidious emergent plant pathogen, future basic and applied research to develop control strategies can be prioritized.

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Grapevine Phenolic Compounds in Xylem Sap and Tissues Are Significantly Altered During Infection by Xylella fastidiosa

Phytopathology ◽

10.1094/phyto-04-12-0074-r ◽

2012 ◽

Vol 102 (9) ◽

pp. 816-826 ◽

Cited By ~ 40

Author(s):

Christopher M. Wallis ◽

Jianchi Chen

Keyword(s):

Phenolic Compounds ◽

Secondary Metabolite ◽

Cell Walls ◽

Condensed Tannins ◽

Large Scale ◽

Xylella Fastidiosa ◽

Xylem Sap ◽

Bacterial Pathogen ◽

Thompson Seedless ◽

Metabolite Production

Pierce's disease of grapevine (PD), caused by the bacterial pathogen Xylella fastidiosa, remains a serious problem for grape production in California and elsewhere. This research examined induction of phenolic compounds in grapevines (‘Thompson Seedless’) infected with X. fastidiosa over a 6-month period. Two months postinoculation with X. fastidiosa, catechin, digalloylquinic acid, and astringin were found at greater levels in xylem sap; multiple catechins, procyanidins, and stilbenoids were found at greater levels in xylem tissues; and precursors to lignin and condensed tannins were found at greater levels in xylem cell walls. However, such large-scale inductions of phenolic compounds were not observed 4 months after inoculation. Six months after inoculation, infected plants had significantly reduced phenolic levels in xylem sap and tissues when compared with control plants, including lowered levels of lignin and condensed tannins. At 6 months, PD symptoms were severe in infected plants and most photosynthetic tissue was abscised. These results suggest that, even though grapevine hosts may initially respond to X. fastidiosa infections with increased production of phenolic compounds, ultimately, PD causes grapevines to enter a state of decline whereby diseased hosts no longer have the resources to support secondary metabolite production, including defense-associated phenolic compounds.

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Radiation-Inactivated Acinetobacter baumannii Vaccine Candidates

Vaccines ◽

10.3390/vaccines9020096 ◽

2021 ◽

Vol 9 (2) ◽

pp. 96

Author(s):

Stephen J. Dollery ◽

Daniel V. Zurawski ◽

Elena K. Gaidamakova ◽

Vera Y. Matrosova ◽

John K. Tobin ◽

...

Keyword(s):

Acinetobacter Baumannii ◽

Treatment Options ◽

Bacterial Pathogen ◽

Multidrug Resistant ◽

Bacterial Cells ◽

Wound Infections ◽

Protein Profiles ◽

Vaccine Candidates ◽

Rich Media ◽

Life Threatening

Acinetobacter baumannii is a bacterial pathogen that is often multidrug-resistant (MDR) and causes a range of life-threatening illnesses, including pneumonia, septicemia, and wound infections. Some antibiotic treatments can reduce mortality if dosed early enough before an infection progresses, but there are few other treatment options when it comes to MDR-infection. Although several prophylactic strategies have been assessed, no vaccine candidates have advanced to clinical trials or have been approved. Herein, we rapidly produced protective whole-cell immunogens from planktonic and biofilm-like cultures of A. baumannii, strain AB5075 grown using a variety of methods. After selecting a panel of five cultures based on distinct protein profiles, replicative activity was extinguished by exposure to 10 kGy gamma radiation in the presence of a Deinococcus antioxidant complex composed of manganous (Mn2+) ions, a decapeptide, and orthophosphate. Mn2+ antioxidants prevent hydroxylation and carbonylation of irradiated proteins, but do not protect nucleic acids, yielding replication-deficient immunogenic A. baumannii vaccine candidates. Mice were immunized and boosted twice with 1.0 × 107 irradiated bacterial cells and then challenged intranasally with AB5075 using two mouse models. Planktonic cultures grown for 16 h in rich media and biofilm cultures grown in static cultures underneath minimal (M9) media stimulated immunity that led to 80–100% protection.

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Revealing the Metabolic Alterations during Biofilm Development of Burkholderia cenocepacia Based on Genome-Scale Metabolic Modeling

Metabolites ◽

10.3390/metabo11040221 ◽

2021 ◽

Vol 11 (4) ◽

pp. 221

Author(s):

Ozlem Altay ◽

Cheng Zhang ◽

Hasan Turkez ◽

Jens Nielsen ◽

Mathias Uhlén ◽

...

Keyword(s):

Systems Biology ◽

Alternative Pathway ◽

Growth Conditions ◽

Pentose Phosphate ◽

Burkholderia Cenocepacia ◽

Bacterial Cells ◽

Metabolic Remodeling ◽

Transcriptomics Data ◽

Biofilm Development ◽

Genome Scale

Burkholderia cenocepacia is among the important pathogens isolated from cystic fibrosis (CF) patients. It has attracted considerable attention because of its capacity to evade host immune defenses during chronic infection. Advances in systems biology methodologies have led to the emergence of methods that integrate experimental transcriptomics data and genome-scale metabolic models (GEMs). Here, we integrated transcriptomics data of bacterial cells grown on exponential and biofilm conditions into a manually curated GEM of B. cenocepacia. We observed substantial differences in pathway response to different growth conditions and alternative pathway susceptibility to extracellular nutrient availability. For instance, we found that blockage of the reactions was vital through the lipid biosynthesis pathways in the exponential phase and the absence of microenvironmental lysine and tryptophan are essential for survival. During biofilm development, bacteria mostly had conserved lipid metabolism but altered pathway activities associated with several amino acids and pentose phosphate pathways. Furthermore, conversion of serine to pyruvate and 2,5-dioxopentanoate synthesis are also identified as potential targets for metabolic remodeling during biofilm development. Altogether, our integrative systems biology analysis revealed the interactions between the bacteria and its microenvironment and enabled the discovery of antimicrobial targets for biofilm-related diseases.

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The plant defense signal galactinol is specifically used as a nutrient by the bacterial pathogen Agrobacterium fabrum

Journal of Biological Chemistry ◽

10.1074/jbc.ra118.001856 ◽

2018 ◽

Vol 293 (21) ◽

pp. 7930-7941 ◽

Cited By ~ 7

Author(s):

Thibault Meyer ◽

Armelle Vigouroux ◽

Magali Aumont-Nicaise ◽

Gilles Comte ◽

Ludovic Vial ◽

...

Keyword(s):

Competitive Advantage ◽

Plant Defense ◽

Higher Plants ◽

Bacterial Pathogen ◽

Binding Mode ◽

Plant Colonization ◽

Plant Metabolites ◽

Tomato Plants ◽

Periplasmic Binding Proteins ◽

Nanomolar Range

The bacterial plant pathogen Agrobacterium fabrum uses periplasmic-binding proteins (PBPs) along with ABC transporters to import a wide variety of plant molecules as nutrients. Nonetheless, how A. fabrum acquires plant metabolites is incompletely understood. Using genetic approaches and affinity measurements, we identified here the PBP MelB and its transporter as being responsible for the uptake of the raffinose family of oligosaccharides (RFO), which are the most widespread d-galactose–containing oligosaccharides in higher plants. We also found that the RFO precursor galactinol, recently described as a plant defense molecule, is imported into Agrobacterium via MelB with nanomolar range affinity. Structural analyses and binding mode comparisons of the X-ray structures of MelB in complex with raffinose, stachyose, galactinol, galactose, and melibiose (a raffinose degradation product) revealed how MelB recognizes the nonreducing end galactose common to all these ligands and that MelB has a strong preference for a two-unit sugar ligand. Of note, MelB conferred a competitive advantage to A. fabrum in colonizing the rhizosphere of tomato plants. Our integrative work highlights the structural and functional characteristics of melibiose and galactinol assimilation by A. fabrum, leading to a competitive advantage for these bacteria in the rhizosphere. We propose that the PBP MelB, which is highly conserved among both symbionts and pathogens from Rhizobiace family, is a major trait in these bacteria required for early steps of plant colonization.

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Addressing the New Global Threat of Xylella fastidiosa

Phytopathology ◽

10.1094/phyto-12-18-0488-fi ◽

2019 ◽

Vol 109 (2) ◽

pp. 172-174 ◽

Cited By ~ 10

Author(s):

R. P. P. Almeida ◽

L. De La Fuente ◽

R. Koebnik ◽

J. R. S. Lopes ◽

S. Parnell ◽

...

Keyword(s):

Xylella Fastidiosa ◽

Severe Disease ◽

Bacterial Pathogen ◽

Host Susceptibility ◽

Detection Methods ◽

Open Communication ◽

Research Themes ◽

Established Disease ◽

Olive Trees ◽

Global Threat

Xylella fastidiosa is one of the most important threats to plant health worldwide. This bacterial pathogen has a long history, causing disease in the Americas on a range of agricultural crops and trees, with severe economic repercussions particularly on grapevine and citrus. In Europe, X. fastidiosa was detected for the first time in 2013 in association with a severe disease affecting olive trees in southern Italy. Subsequent mandatory surveys throughout Europe led to discoveries in France and Spain in various host species and environments. Detection of additional introductions of X. fastidiosa continue to be reported from Europe, for example from northern Italy in late 2018. These events are leading to a sea change in research, monitoring and management efforts as exemplified by the articles in this Focus Issue . X. fastidiosa is part of complex pathosystems together with hosts and vectors. Although certain X. fastidiosa subspecies and environments have been well studied, particularly those that pertain to established disease in North and South America, this represents only a fraction of the existing genetic, epidemiological, and ecological diversity. This Focus Issue highlights some of the key challenges that must be overcome to address this new global threat, recent advances in understanding the pathosystem, and steps toward improved disease control. It brings together the broad research themes needed to address the global threat of X. fastidiosa, encompassing topics from host susceptibility and resistance, genome sequencing, detection methods, transmission by vectors, epidemiological drivers, chemical and biological control, to public databases and social sciences. Open communication and collaboration among scientists, stakeholders, and the general public from different parts of the world will pave the path to novel ideas to understand and combat this pathogen.

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Citrus and Coffee Strains of Xylella fastidiosa Induce Pierce's Disease in Grapevine

Plant Disease ◽

10.1094/pdis.2002.86.11.1206 ◽

2002 ◽

Vol 86 (11) ◽

pp. 1206-1210 ◽

Cited By ~ 28

Author(s):

W.-B Li ◽

C. -H. Zhou ◽

W. D. Pria ◽

D. C. Teixeira ◽

V. S. Miranda ◽

...

Keyword(s):

United States ◽

Sequence Data ◽

Xylella Fastidiosa ◽

Experimental System ◽

The United States ◽

Full Genome Sequence ◽

Pierce's Disease ◽

Plant Colonization ◽

Pierce’S Disease ◽

Citrus Groves

Xylella fastidiosa causes citrus variegated chlorosis (CVC) disease in Brazil and Pierce's disease of grapevines in the United States. Both of these diseases cause significant production problems in the respective industries. The recent establishment of the glassy-winged sharpshooter in California has radically increased the threat posed by Pierce's disease to California viticulture. Populations of this insect reach very high levels in citrus groves in California and move from the orchards into the vineyards, where they acquire inoculum and spread Pierce's disease in the vineyards. Here we show that strains of X. fastidiosa isolated from diseased citrus and coffee in Brazil can incite symptoms of Pierce's disease after mechanical inoculation into seven commercial Vitis vinifera varieties grown in Brazil and California. Thus, any future introduction of the CVC strains of X. fastidiosa into the United States would pose a threat to both the sweet orange and grapevine industries. Previous work has clearly shown that the strains of X. fastidiosa isolated from Pierce's disease- and CVC-affected plants are the most distantly related of all strains in the diverse taxon X. fastidiosa. The ability of citrus strains of X. fastidiosa to incite disease in grapevine is therefore surprising and creates an experimental system with which to dissect mechanisms used by X. fastidiosa in plant colonization and disease development using the full genome sequence data that has recently become available for both the citrus and grapevine strains of this pathogen.

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