The Epidemiology of Xylella fastidiosa; A Perspective on Current Knowledge and Framework to Investigate Plant Host–Vector–Pathogen Interactions

Insect-transmitted plant diseases caused by viruses, phytoplasmas, and bacteria share many features in common regardless of the causal agent. This perspective aims to show how a model framework, developed originally for plant virus diseases, can be modified for the case of diseases incited by Xylella fastidiosa. In particular, the model framework enables the specification of a simple but quite general invasion criterion defined in terms of key plant, pathogen, and vector parameters and, importantly, their interactions, which determine whether or not an incursion or isolated outbreak of a pathogen will lead to establishment, persistence, and subsequent epidemic development. Hence, this approach is applicable to the wide range of X. fastidiosa-incited diseases that have recently emerged in southern Europe, each with differing host plant, pathogen subspecies, and vector identities. Of particular importance are parameters relating to vector abundance and activity, transmission characteristics, and behavior in relation to preferences for host infection status. Some gaps in knowledge with regard to the developing situation in Europe are noted.

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Transcriptomic Analysis of Orange Fruit Treated with Pomegranate Peel Extract (PGE)

Plants ◽

10.3390/plants8040101 ◽

2019 ◽

Vol 8 (4) ◽

pp. 101 ◽

Cited By ~ 5

Author(s):

Imen Belgacem ◽

Sonia Pangallo ◽

Ahmed Abdelfattah ◽

Flora V. Romeo ◽

Santa O. Cacciola ◽

...

Keyword(s):

Gene Ontology ◽

Plant Diseases ◽

Pathway Enrichment Analysis ◽

Plant Host ◽

Pomegranate Peel ◽

Transcriptomic Response ◽

Wide Range ◽

Orange Fruit ◽

Pomegranate Peel Extract ◽

Peel Extract

A Pomegranate Peel Extract (PGE) has been proposed as a natural antifungal substance with a wide range of activity against plant diseases. Previous studies showed that the extract has a direct antimicrobial activity and can elicit resistance responses in plant host tissues. In the present study, the transcriptomic response of orange fruit toward PGE treatments was evaluated. RNA-seq analyses, conducted on wounded fruits 0, 6, and 24 h after PGE applications, showed a significantly different transcriptome in treated oranges as compared to control samples. The majority (273) of the deferentially expressed genes (DEGs) were highly up-regulated compared to only 8 genes that were down-regulated. Gene Ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis showed the involvement of 1233 gene ontology (GO) terms and 35 KEGG metabolic pathways. Among these, important defense pathways were induced and antibiotic biosynthesis was the most enriched one. These findings may explain the underlying preventive and curative activity of PGE against plant diseases.

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Overexpression of mqsR in Xylella fastidiosa Leads to a Priming Effect of Cells to Copper Stress Tolerance

Frontiers in Microbiology ◽

10.3389/fmicb.2021.712564 ◽

2021 ◽

Vol 12 ◽

Author(s):

Isis Gabriela Barbosa Carvalho ◽

Marcus Vinicius Merfa ◽

Natália Sousa Teixeira-Silva ◽

Paula Maria Moreira Martins ◽

Marco Aurélio Takita ◽

...

Keyword(s):

Pathogenic Bacteria ◽

Current Knowledge ◽

Xylella Fastidiosa ◽

Cell Formation ◽

Cell Aggregation ◽

Plant Diseases ◽

Copper Tolerance ◽

Copper Stress ◽

Economic Damage ◽

Environmental Damage

Copper-based compounds are widely used in agriculture as a chemical strategy to limit the spread of multiple plant diseases; however, the continuous use of this heavy metal has caused environmental damage as well as the development of copper-resistant strains. Thus, it is important to understand how the bacterial phytopathogens evolve to manage with this metal in the field. The MqsRA Toxin–Antitoxin system has been recently described for its function in biofilm formation and copper tolerance in Xylella fastidiosa, a plant-pathogen bacterium responsible for economic damage in several crops worldwide. Here we identified differentially regulated genes by X. fastidiosa MqsRA by assessing changes in global gene expression with and without copper. Results show that mqsR overexpression led to changes in the pattern of cell aggregation, culminating in a global phenotypic heterogeneity, indicative of persister cell formation. This phenotype was also observed in wild-type cells but only in the presence of copper. This suggests that MqsR regulates genes that alter cell behavior in order to prime them to respond to copper stress, which is supported by RNA-Seq analysis. To increase cellular tolerance, proteolysis and efflux pumps and regulator related to multidrug resistance are induced in the presence of copper, in an MqsR-independent response. In this study we show a network of genes modulated by MqsR that is associated with induction of persistence in X. fastidiosa. Persistence in plant-pathogenic bacteria is an important genetic tolerance mechanism still neglected for management of phytopathogens in agriculture, for which this work expands the current knowledge and opens new perspectives for studies aiming for a more efficient control in the field.

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An Experimental Test of the Host-Plant Range of Nonrecombinant Strains of North American Xylella fastidiosa subsp. multiplex

Phytopathology ◽

10.1094/phyto-07-18-0252-fi ◽

2019 ◽

Vol 109 (2) ◽

pp. 294-300 ◽

Cited By ~ 15

Author(s):

Leonard Nunney ◽

Hamid Azad ◽

Richard Stouthamer

Keyword(s):

Homologous Recombination ◽

Host Range ◽

Xylella Fastidiosa ◽

Sequence Type ◽

Host Specialization ◽

Washington Dc ◽

Plant Host ◽

Wide Range ◽

Novel Host ◽

Different Strains

Nonrecombinant strains of Xylella fastidiosa subsp. multiplex (those lacking evidence of significant intersubspecific homologous recombination) infect the xylem of a wide range of native and nonnative trees in North America. However, the degree to which different strains have a specialized host range remains poorly understood. We tested eight strains isolated from five different tree species (almond, olive, sweetgum, and plum in California and oak in Washington, DC). Experiments were conducted in greenhouses in Riverside, CA, and each strain was tested on 11 to 15 of the 17 plant species tested. Hosts infected by the most strains were plum (5 of 8 strains) and almond (4 of 8), while their congener peach was only infected by 1 of 8. No strains infected oleander or mulberry. All strains successfully infected their original host, with peach, olive (1 of 7), and sweetgum (2 of 6) only infected by such strains. Of the 90 total strain–novel-host combinations tested, 11 resulted in unambiguous infection, 2 gave ambiguous results, and the remaining 77 failed to result in symptoms or bacterial spread. All eight strains had a unique host range, including two pairs of strains with the same multilocus sequence typing sequence type, providing strong evidence of extensive plant-host specialization. There was little evidence that host relatedness was driving host specificity.

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Conjugative Plasmid Transfer in Xylella fastidiosa Is Dependent on tra and trb Operon Functions

Journal of Bacteriology ◽

10.1128/jb.00388-17 ◽

2017 ◽

Vol 199 (21) ◽

Cited By ~ 5

Author(s):

Lindsey P. Burbank ◽

Christopher R. Van Horn

Keyword(s):

Gene Transfer ◽

Plant Pathogen ◽

Natural Transformation ◽

Xylella Fastidiosa ◽

Plasmid Transfer ◽

Conjugative Plasmid ◽

Broad Host Range ◽

Donor Strain ◽

Content Type ◽

Wide Range

ABSTRACT The insect-transmitted plant pathogen Xylella fastidiosa is capable of efficient horizontal gene transfer (HGT) and recombination. Natural transformation occurs at high rates in X. fastidiosa, but there also is evidence that certain strains of X. fastidiosa carry native plasmids equipped with transfer and mobilization genes, suggesting conjugation as an additional mechanism of HGT in some instances. Two operons, tra and trb, putatively encoding a conjugative type IV secretion system, are found in some but not all X. fastidiosa isolates, often on native plasmids. X. fastidiosa strains that carry the conjugative transfer genes can belong to different subspecies and frequently differ in host ranges. Using X. fastidiosa strain M23 (X. fastidiosa subsp. fastidiosa) or Dixon (X. fastidiosa subsp. multiplex) as the donor strain and Temecula (X. fastidiosa subsp. fastidiosa) as the recipient strain, plasmid transfer was characterized using the mobilizable broad-host-range vector pBBR5pemIK. Transfer of plasmid pBBR5pemIK was observed under in vitro conditions with both donor strains and was dependent on both tra and trb operon functions. A conjugative mechanism likely contributes to gene transfer between diverse strains of X. fastidiosa, possibly facilitating adaptation to new environments or different hosts. IMPORTANCE Xylella fastidiosa is an important plant pathogen worldwide, infecting a wide range of different plant species. The emergence of new diseases caused by X. fastidiosa, or host switching of existing strains, is thought to be primarily due to the high frequency of HGT and recombination in this pathogen. Transfer of plasmids by a conjugative mechanism enables movement of larger amounts of genetic material at one time, compared with other routes of gene transfer such as natural transformation. Establishing the prevalence and functionality of this mechanism in X. fastidiosa contributes to a better understanding of HGT, adaptation, and disease emergence in this diverse pathogen.

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Natural Competence and Recombination in the Plant Pathogen Xylella fastidiosa

Applied and Environmental Microbiology ◽

10.1128/aem.00730-11 ◽

2011 ◽

Vol 77 (15) ◽

pp. 5278-5284 ◽

Cited By ~ 41

Author(s):

Stephanie H. Kung ◽

Rodrigo P. P. Almeida

Keyword(s):

Plant Pathogen ◽

Xylella Fastidiosa ◽

Genetic Material ◽

Plant Diseases ◽

Exogenous Dna ◽

Content Type ◽

Genomic Studies ◽

Different Strains ◽

Exogenous Plasmid

ABSTRACTHomologous recombination is one of many forces contributing to the diversity, adaptation, and emergence of pathogens. For naturally competent bacteria, transformation is one possible route for the acquisition of novel genetic material. This study demonstrates thatXylella fastidiosa, a generalist bacterial plant pathogen responsible for many emerging plant diseases, is naturally competent and able to homologously recombine exogenous DNA into its genome. Several factors that affect transformation and recombination efficiencies, such as nutrient availability, growth stage, and methylation of transforming DNA, were identified. Recombination was observed in at least one out of every 106cells when exogenous plasmid DNA was supplied and one out of every 107cells when different strains were grown togetherin vitro. Based on previous genomic studies and experimental data presented here, there is mounting evidence that recombination can occur at relatively high rates and could play a large role in shaping the genetic diversity ofX. fastidiosa.

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The Iron Stimulon of Xylella fastidiosa Includes Genes for Type IV Pilus and Colicin V-Like Bacteriocins

Journal of Bacteriology ◽

10.1128/jb.01495-07 ◽

2008 ◽

Vol 190 (7) ◽

pp. 2368-2378 ◽

Cited By ~ 30

Author(s):

Paulo A. Zaini ◽

Andréa C. Fogaça ◽

Fernanda G. N. Lupo ◽

Helder I. Nakaya ◽

Ricardo Z. N. Vêncio ◽

...

Keyword(s):

Large Scale ◽

Xylella Fastidiosa ◽

Cell Structure ◽

Iron Concentration ◽

Etiologic Agent ◽

Plant Diseases ◽

Mobility Shift ◽

Wide Range ◽

Colicin V ◽

Strain 9A5c

ABSTRACTXylella fastidiosais the etiologic agent of a wide range of plant diseases, including citrus variegated chlorosis (CVC), a major threat to citrus industry. The genomes of several strains of this phytopathogen were completely sequenced, enabling large-scale functional studies. DNA microarrays representing 2,608 (91.6%) coding sequences (CDS) ofX. fastidiosaCVC strain 9a5c were used to investigate transcript levels during growth with different iron availabilities. When treated with the iron chelator 2,2′-dipyridyl, 193 CDS were considered up-regulated and 216 were considered down-regulated. Upon incubation with 100 μM ferric pyrophosphate, 218 and 256 CDS were considered up- and down-regulated, respectively. Differential expression for a subset of 44 CDS was further evaluated by reverse transcription-quantitative PCR. Several CDS involved with regulatory functions, pathogenicity, and cell structure were modulated under both conditions assayed, suggesting that major changes in cell architecture and metabolism occur whenX. fastidiosacells are exposed to extreme variations in iron concentration. Interestingly, the modulated CDS include those related to colicin V-like bacteriocin synthesis and secretion and to functions of pili/fimbriae. We also investigated the contribution of the ferric uptake regulator Fur to the iron stimulon ofX. fastidiosa. The promoter regions of the strain 9a5c genome were screened for putative Fur boxes, and candidates were analyzed by electrophoretic mobility shift assays. Taken together, our data support the hypothesis that Fur is not solely responsible for the modulation of the iron stimulon ofX. fastidiosa, and they present novel evidence for iron regulation of pathogenicity determinants.

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Tickets for the Inclusive Museum

The Oxford Handbook of Deaf Studies in Learning and Cognition ◽

10.1093/oxfordhb/9780190054045.013.23 ◽

2020 ◽

pp. 390-406

Author(s):

Magda Nikolaraizi ◽

Charikleia Kanari ◽

Marc Marschark

Keyword(s):

Hard Of Hearing ◽

Learning Experiences ◽

Learning Needs ◽

Participatory Learning ◽

Maximum Benefit ◽

Wide Range ◽

The Right ◽

Physical Features ◽

And Behavior

In recent years, museums of various kinds have broadened their mission and made systematic efforts to develop a dynamic role in learning by offering a wide range of less formal experiences for individuals with diverse characteristics, including individuals who are deaf or hard-of-hearing (DHH). Despite the worthwhile efforts, in the case of DHH individuals, museums frequently neglect to consider their unique communication, cognitive, cultural, and learning characteristics, thus limiting their access and opportunities for fully experiencing what museums have to offer. This chapter examines the potential for creating accessible museum environments and methods that reflect an understanding of the diverse communication, cognitive, cultural, and learning needs of DHH visitors, all of which enhance their access and participation in the museum activities. The role of the physical features of museum spaces for the access and behavior of DHH visitors is emphasized, together with attention to exhibition methods and the communication and cognitive challenges that need to be considered so DHH visitors can get the maximum benefit. The chapter emphasizes the right of individuals who are DHH to nonformal learning and analyzes how museums could become more accessible to DHH individuals by designing, from the beginning, participatory learning experiences that address their diverse needs.

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Fitness of Herbicide-Resistant Weeds: Current Knowledge and Implications for Management

Plants ◽

10.3390/plants8110469 ◽

2019 ◽

Vol 8 (11) ◽

pp. 469 ◽

Cited By ~ 5

Author(s):

Vila-Aiub

Keyword(s):

Life History ◽

Herbicide Resistance ◽

Management Practices ◽

Current Knowledge ◽

Resistance Management ◽

Fitness Cost ◽

Plant Fitness ◽

Resistance Mutations ◽

Fitness Costs ◽

Wide Range

Herbicide resistance is the ultimate evidence of the extraordinary capacity of weeds to evolve under stressful conditions. Despite the extraordinary plant fitness advantage endowed by herbicide resistance mutations in agroecosystems under herbicide selection, resistance mutations are predicted to exhibit an adaptation cost (i.e., fitness cost), relative to the susceptible wild-type, in herbicide untreated conditions. Fitness costs associated with herbicide resistance mutations are not universal and their expression depends on the particular mutation, genetic background, dominance of the fitness cost, and environmental conditions. The detrimental effects of herbicide resistance mutations on plant fitness may arise as a direct impact on fitness-related traits and/or coevolution with changes in other life history traits that ultimately may lead to fitness costs under particular ecological conditions. This brings the idea that a “lower adaptive value” of herbicide resistance mutations represents an opportunity for the design of resistance management practices that could minimize the evolution of herbicide resistance. It is evident that the challenge for weed management practices aiming to control, minimize, or even reverse the frequency of resistance mutations in the agricultural landscape is to “create” those agroecological conditions that could expose, exploit, and exacerbate those life history and/or fitness traits affecting the evolution of herbicide resistance mutations. Ideally, resistance management should implement a wide range of cultural practices leading to environmentally mediated fitness costs associated with herbicide resistance mutations.

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Transfer of Plasmid DNA to Clinical Coagulase-Negative Staphylococcal Pathogens by Using a Unique Bacteriophage

Applied and Environmental Microbiology ◽

10.1128/aem.04190-14 ◽

2015 ◽

Vol 81 (7) ◽

pp. 2481-2488 ◽

Cited By ~ 19

Author(s):

Volker Winstel ◽

Petra Kühner ◽

Bernhard Krismer ◽

Andreas Peschel ◽

Holger Rohde

Keyword(s):

Plasmid Dna ◽

Genetic Manipulation ◽

Current Knowledge ◽

Virulence Determinants ◽

Coagulase Negative Staphylococci ◽

Reliable Technique ◽

Content Type ◽

Research Activities ◽

Wide Range ◽

Genetic Barriers

ABSTRACTGenetic manipulation of emerging bacterial pathogens, such as coagulase-negative staphylococci (CoNS), is a major hurdle in clinical and basic microbiological research. Strong genetic barriers, such as restriction modification systems or clustered regularly interspaced short palindromic repeats (CRISPR), usually interfere with available techniques for DNA transformation and therefore complicate manipulation of CoNS or render it impossible. Thus, current knowledge of pathogenicity and virulence determinants of CoNS is very limited. Here, a rapid, efficient, and highly reliable technique is presented to transfer plasmid DNA essential for genetic engineering to important CoNS pathogens from a uniqueStaphylococcus aureusstrain via a specificS. aureusbacteriophage, Φ187. Even strains refractory to electroporation can be transduced by this technique once donor and recipient strains share similar Φ187 receptor properties. As a proof of principle, this technique was used to delete the alternative transcription factor sigma B (SigB) via allelic replacement in nasal and clinicalStaphylococcus epidermidisisolates at high efficiencies. The described approach will allow the genetic manipulation of a wide range of CoNS pathogens and might inspire research activities to manipulate other important pathogens in a similar fashion.

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Drivers of Infectious Disease Seasonality: Potential Implications for COVID-19

Journal of Biological Rhythms ◽

10.1177/0748730420987322 ◽

2021 ◽

pp. 074873042098732

Author(s):

N. Kronfeld-Schor ◽

T. J. Stevenson ◽

S. Nickbakhsh ◽

E. S. Schernhammer ◽

X. C. Dopico ◽

...

Keyword(s):

Infectious Disease ◽

Infectious Diseases ◽

Multidisciplinary Approach ◽

Preliminary Assessment ◽

Epidemiological Evidence ◽

Wide Range ◽

Human Coronaviruses ◽

Induced Changes ◽

And Behavior ◽

Timing Phase

Not 1 year has passed since the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19). Since its emergence, great uncertainty has surrounded the potential for COVID-19 to establish as a seasonally recurrent disease. Many infectious diseases, including endemic human coronaviruses, vary across the year. They show a wide range of seasonal waveforms, timing (phase), and amplitudes, which differ depending on the geographical region. Drivers of such patterns are predominantly studied from an epidemiological perspective with a focus on weather and behavior, but complementary insights emerge from physiological studies of seasonality in animals, including humans. Thus, we take a multidisciplinary approach to integrate knowledge from usually distinct fields. First, we review epidemiological evidence of environmental and behavioral drivers of infectious disease seasonality. Subsequently, we take a chronobiological perspective and discuss within-host changes that may affect susceptibility, morbidity, and mortality from infectious diseases. Based on photoperiodic, circannual, and comparative human data, we not only identify promising future avenues but also highlight the need for further studies in animal models. Our preliminary assessment is that host immune seasonality warrants evaluation alongside weather and human behavior as factors that may contribute to COVID-19 seasonality, and that the relative importance of these drivers requires further investigation. A major challenge to predicting seasonality of infectious diseases are rapid, human-induced changes in the hitherto predictable seasonality of our planet, whose influence we review in a final outlook section. We conclude that a proactive multidisciplinary approach is warranted to predict, mitigate, and prevent seasonal infectious diseases in our complex, changing human-earth system.

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