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

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

Phytopathology ◽

10.1094/phyto-10-16-0374-r ◽

2017 ◽

Vol 107 (4) ◽

pp. 388-394 ◽

Cited By ~ 5

Author(s):

Lindsey P. Burbank ◽

Drake C. Stenger

Keyword(s):

Xylella Fastidiosa ◽

Xylem Sap ◽

Bacterial Pathogen ◽

Growth Conditions ◽

Plant Colonization ◽

Insect Vector ◽

Bacterial Cells ◽

Knockout Mutant ◽

Bacterial Proliferation ◽

Systemic Spread

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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Electroanalytical Techniques for the Detection of Selenium as a Biologically and Environmentally Significant Analyte—A Short Review

Molecules ◽

10.3390/molecules26061768 ◽

2021 ◽

Vol 26 (6) ◽

pp. 1768

Author(s):

Miroslav Rievaj ◽

Eva Culková ◽

Damiána Šandorová ◽

Zuzana Lukáčová-Chomisteková ◽

Renata Bellová ◽

...

Keyword(s):

Oxidative Stress ◽

Essential Element ◽

Analytical Techniques ◽

High Sensitivity ◽

Stripping Voltammetry ◽

Short Review ◽

Electroanalytical Methods ◽

High Concentrations ◽

Speed Of Analysis

This short review deals with the properties and significance of the determination of selenium, which is in trace amounts an essential element for animals and humans, but toxic at high concentrations. It may cause oxidative stress in cells, which leads to the chronic disease called selenosis. Several analytical techniques have been developed for its detection, but electroanalytical methods are advantageous due to simple sample preparation, speed of analysis and high sensitivity of measurements, especially in the case of stripping voltammetry very low detection limits even in picomoles per liter can be reached. A variety of working electrodes based on mercury, carbon, silver, platinum and gold materials were applied to the analysis of selenium in various samples. Only selenium in oxidation state + IV is electroactive therefore the most of voltammetric determinations are devoted to it. However, it is possible to detect also other forms of selenium by indirect electrochemistry approach.

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Media composition affects seed dormancy, apical dominance and phenolic profile of Knautia sarajevensis (Dipsacaceae), Bosnian endemic

Acta Botanica Croatica ◽

10.1515/botcro-2017-0011 ◽

2018 ◽

Vol 77 (1) ◽

pp. 70-79 ◽

Cited By ~ 1

Author(s):

Erna Karalija ◽

Sanja Ćavar Zeljković ◽

Petr Tarkowski ◽

Edina Muratović ◽

Adisa Parić

Keyword(s):

Apical Dominance ◽

Germination Rate ◽

Natural Habitat ◽

Basal Medium ◽

Shoot Proliferation ◽

Mineral Nutrient ◽

Total Phenolic ◽

Endemic Plant ◽

High Concentrations

AbstractKnautia sarajevensisis an endemic plant of the Dinaric Alps and is mainly distributed on Bosnian Mountains. Due to the quite large flower heads and easy maintenance, this plant has a potential use as a substitute ornamental plant forK. arvensisin perennial beds. The current study evaluated the germination process in different treatments in an attempt to suppress dormancy and increase germination rate, and to develop a successful protocol for micropropagation. An over 60% germination rate was achieved through cultivation of seeds on MS basal medium with reduced mineral nutrient composition and the absence of sucrose. On the other hand, a below 10% germination rate was achieved with untreated seeds. Suppression of apical dominance was achieved through application of high concentrations of kinetin, apical shoot decapitation or cultivation of shoots in liquid media. Overall, liquid cultures were more successful as a micropropagation system for this plant. Shoots spontaneously developed roots on multiplication treatments and were successfully acclimatized. Moreover, phenolic compound profile was analysed in the light of the possible medicinal potential of this plant. Variable amounts of total phenolic compounds as well as individual phenolics were recorded, according to treatment and solidification of media. An increase in rosmarinic acid content was reported for kinetin treatments and acclimatized plants comparing to mother plants in natural habitat. The present study shows that choice of cytokinin concentration, explant type as well as culture type influences not only shoot proliferation and apical dominance suppression but alsoin vitroproduction of phenolics.

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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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Isotopic Discriminations During the Accumulation of Nitrogen by Soybeans

Functional Plant Biology ◽

10.1071/pp9880407 ◽

1988 ◽

Vol 15 (3) ◽

pp. 407 ◽

Cited By ~ 40

Author(s):

FJ Bergersen ◽

MB Peoples ◽

GL Turner

Keyword(s):

N2 Fixation ◽

Root Nodules ◽

Xylem Sap ◽

Vacuum Treatment ◽

Natural Abundance ◽

Mineral Nutrient ◽

Similar Time ◽

Total N ◽

Plant Nitrogen ◽

Nitrate Treatment

Soybeans were grown in a glasshouse in sand-vermiculite medium supplied daily with a mineral nutrient solution essentially free of combined N or containing 5 mM nitrate of known 15N abundance. The natural abundance of 15N in parts of plants and in nitrogen remaining in the medium was determined from 15 days after planting until fruiting. In nodulated plants completely dependent on N2 fixation for growth, the δ15N of plant nitrogen was uniformly negative at 56 days (overall mean: -0.90� 0.17) after adjustment for the effect of seed nitrogen. The δ15N of root nodules increased with time (max. 9.6‰), as that of shoots declined (min. - 1.3 ‰). The δ15N of every mainstem trifoliolate leaf and of the first (unifoliolate) leaf declined from initially positive values (0.5 to 2 ‰) to about - 2‰ with similar time courses, irrespective of the time of initiation. There were no significant losses of N from the plants during growth. There were differences between the δ15N of the total N of root-bleeding xylem sap and of sap extracted by vacuum treatment of stems. These were due to differences between the proportions of ureide-N and amino-N and between the δ15N values of these components. When nodulated plants were supplied daily with 5 mM nitrate (δ15N = 7.68‰) between 21 and 35 days, N2 fixation was reduced to 63% of N assimilated but growth and accumulation of nitrogen were affected little. Following removal of nitrate, there were changes in growth which led to enhanced nodulation and N2 fixation. The δ15N of the total N of trifoliolate leaves which were initiated or expanded before or during the period of nitrate treatment remained positive; those expanded or initiated after the treatment became negative in δ15N, as in the corresponding leaves of untreated nodulated plants. The δ15N of nodules was unaffected by the nitrate treatment. In plants (non-nod. Clark '63) supplied continuously with nitrate, the δ15N of the total N of entire plants rose quickly from values for seeds, but to values significantly higher than in the nitrate. These results are discussed in relation to the effects on the use of 15N natural abundance data for estimating utilisation of atmospheric N2 by nodulated plants.

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Copper Supplementation in Watering Solution Reaches the Xylem But Does Not Protect Tobacco Plants Against Xylella fastidiosa Infection

Plant Disease ◽

10.1094/pdis-08-19-1748-re ◽

2020 ◽

Vol 104 (3) ◽

pp. 724-730 ◽

Cited By ~ 2

Author(s):

Qing Ge ◽

Paul A. Cobine ◽

Leonardo De La Fuente

Keyword(s):

Biofilm Formation ◽

Inductively Coupled Plasma ◽

Tap Water ◽

Xylella Fastidiosa ◽

In Vitro Study ◽

Optical Emission ◽

In Planta ◽

Inductively Coupled ◽

High Concentrations

Xylella fastidiosa is a xylem-limited plant pathogenic bacterium that causes disease in many crops worldwide. Copper (Cu) is an antimicrobial agent widely used on X. fastidiosa hosts to control other diseases. Although the effects of Cu for control of foliar pathogens are well known, it is less studied on xylem-colonizing pathogens. Previous results from our group showed that low concentrations of CuSO4 increased biofilm formation, whereas high concentrations inhibited biofilm formation and growth in vitro. In this study, we conducted in planta experiments to determine the influence of Cu in X. fastidiosa infection using tobacco as a model. X. fastidiosa-infected and noninfected plants were watered with tap water or with water supplemented with 4 mM or 8 mM of CuSO4. Symptom progression was assessed, and sap and leaf ionome analysis was performed by inductively coupled plasma with optical emission spectroscopy. Cu uptake was confirmed by increased concentrations of Cu in the sap of plants treated with CuSO4-amended water. Leaf scorch symptoms in Cu-supplemented plants showed a trend toward more severe at later time points. Quantification of total and viable X. fastidiosa in planta indicated that CuSO4-amended treatments did not inhibit but slightly increased the growth of X. fastidiosa. Cu in sap was in the range of concentrations that promote X. fastidiosa biofilm formation according to our previous in vitro study. Based on these results, we proposed that the plant Cu homeostasis machinery controls the level of Cu in the xylem, preventing it from becoming elevated to a level that would lead to bacterial inhibition.

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Contractile dysfunction of atrial myocardium from endotoxin-shocked guinea pigs

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1981.240.6.h954 ◽

1981 ◽

Vol 240 (6) ◽

pp. H954-H962 ◽

Cited By ~ 1

Author(s):

J. L. Parker ◽

H. R. Adams

Keyword(s):

Heart Muscle ◽

Guinea Pigs ◽

Endotoxin Shock ◽

Disease State ◽

Channel Blockers ◽

Inotropic Effects ◽

Cardiac Depression ◽

Increased Sensitivity ◽

High Concentrations ◽

And Control

Atrial muscle isolated from guinea pigs subjected to Escherichia coli endotoxin shock was used to study the myocardial changes associated with this experimental disease state. Isometric contractile tension and its first derivative (dT/dt) consistently were depressed by about 45% in muscle from the shock group (P less than 0.001), but contraction time intervals of the shock tissues were not significantly altered. The inotropic deficit of shock was completely antagonized by high concentrations of Ca2+ (greater than 4.5 mM). However, the maximal positive inotropic response to increased frequency of stimulation (0.1-2.2 Hz) only partially antagonized shock-induced cardiac depression. Heart muscle from shocked animals exhibited increased sensitivity to the negative inotropic effects of Mn2+, low Ca2+, and gentamicin; recovery from the depressant actions of these agents was prolonged 3.6- to 4.8-fold in shock. However, the negative inotropic potency of slow Ca2+ channel blockers, D 600 and nifedipine, was unaffected by shock. Similarly, studies with an isoproterenol-activated slow Ca2+ channel technique demonstrated equivalent inotropic responses of shock and control heart muscle. Present data provide evidence for a disruption of myocardial Ca2+ metabolism associated with endotoxin-induced inotropic depression of the heart but suggest that slow Ca2+ channels of the sarcolemma remain functional in this disease state.

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Screen-Printed f-EM Sensors Based on Two Chelating-Polymers and a Metal Oxide for the Continuous Detection of Cu Ions in Surface Water

Proceedings ◽

10.3390/proceedings2130828 ◽

2018 ◽

Vol 2 (13) ◽

pp. 828 ◽

Cited By ~ 3

Author(s):

Ilaria Frau ◽

Stephen Wylie ◽

Patrick Byrne ◽

Jeff Cullen ◽

Olga Korostynska ◽

...

Keyword(s):

Continuous Monitoring ◽

Essential Element ◽

Potential Method ◽

Microwave Spectroscopy ◽

Specific Response ◽

Combined Method ◽

Low Concentrations ◽

High Concentrations ◽

Cu Ions ◽

Chelating Polymers

Pollutants affect water worldwide and consequently present a risk to both the environment and to human health. Cu is an essential element for many organisms, but becomes toxic at relatively high concentrations. Current laboratory-based methods are not able to monitor water quality continuously, as they require laborious sampling and offline monitoring. A potential method that is capable to addressing this problem, guaranteeing the continuous monitoring of water resources, is the integration of microwave spectroscopy with functionalised electromagnetic (f-EM) sensors. The feasibility of using this combined method for achieving a more specific response toward low concentrations of Cu has been demonstrated.

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Transmission of Xylella fastidiosa to Grapevine by the Meadow Spittlebug

Phytopathology ◽

10.1094/phyto-05-16-0202-r ◽

2016 ◽

Vol 106 (11) ◽

pp. 1285-1290 ◽

Cited By ~ 21

Author(s):

D. Cornara ◽

A. Sicard ◽

A. R. Zeilinger ◽

F. Porcelli ◽

A. H. Purcell ◽

...

Keyword(s):

Xylella Fastidiosa ◽

Transmission Efficiency ◽

Access Time ◽

Insect Vectors ◽

Bacterial Populations ◽

Plant Infection ◽

Basic Parameters ◽

Pathogen Populations ◽

The Relationship ◽

Meadow Spittlebug

There is little information available on Xylella fastidiosa transmission by spittlebugs (Hemiptera, Cercopoidea). This group of insect vectors may be of epidemiological relevance in certain diseases, so it is important to better understand the basic parameters of X. fastidiosa transmission by spittlebugs. We used grapevines as a host plant and the aphrophorid Philaenus spumarius as a vector to estimate the effect of plant access time on X. fastidiosa transmission to plants; in addition, bacterial population estimates in the heads of vectors were determined and correlated with plant infection status. Results show that transmission efficiency of X. fastidiosa by P. spumarius increased with plant access time, similarly to insect vectors in another family (Hemiptera, Cicadellidae). Furthermore, a positive correlation between pathogen populations in P. spumarius and transmission to plants was observed. Bacterial populations in insects were one to two orders of magnitude lower than those observed in leafhopper vectors, and population size peaked within 3 days of plant access period. These results suggest that P. spumarius has either a limited number of sites in the foregut that may be colonized, or that fluid dynamics in the mouthparts of these insects is different from that in leafhoppers. Altogether our results indicate that X. fastidiosa transmission by spittlebugs is similar to that by leafhoppers. In addition, the relationship between cell numbers in vectors and plant infection may have under-appreciated consequences to pathogen spread.

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Calcium-Enhanced Twitching Motility in Xylella fastidiosa Is Linked to a Single PilY1 Homolog

Applied and Environmental Microbiology ◽

10.1128/aem.02153-14 ◽

2014 ◽

Vol 80 (23) ◽

pp. 7176-7185 ◽

Cited By ~ 23

Author(s):

Luisa F. Cruz ◽

Jennifer K. Parker ◽

Paul A. Cobine ◽

Leonardo De La Fuente

Keyword(s):

Xylella Fastidiosa ◽

Xylem Sap ◽

Active Movement ◽

Binding Motif ◽

Twitching Motility ◽

Structural Protein ◽

Plant Host ◽

Content Type ◽

Type Iv ◽

Functional Differences

ABSTRACTThe plant-pathogenic bacteriumXylella fastidiosais restricted to the xylem vessel environment, where mineral nutrients are transported through the plant host; therefore, changes in the concentrations of these elements likely impact the growth and virulence of this bacterium. Twitching motility, dependent on type IV pili (TFP), is required for movement against the transpiration stream that results in basipetal colonization. We previously demonstrated that calcium (Ca) increases the motility ofX. fastidiosa, although the mechanism was unknown. PilY1 is a TFP structural protein recently shown to bind Ca and to regulate twitching and adhesion in bacterial pathogens of humans. Sequence analysis identified threepilY1homologs inX. fastidiosa(PD0023, PD0502, and PD1611), one of which (PD1611) contains a Ca-binding motif. Separate deletions of PD0023 and PD1611 resulted in mutants that still showed twitching motility and were not impaired in attachment or biofilm formation. However, the response of increased twitching at higher Ca concentrations was lost in thepilY1-1611 mutant. Ca does not modulate the expression of any of theX. fastidiosaPilY1 homologs, although it increases the expression of the retraction ATPasepilTduring active movement. The evidence presented here suggests functional differences between the PilY1 homologs, which may provideX. fastidiosawith an adaptive advantage in environments with high Ca concentrations, such as xylem sap.

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