scholarly journals Factors Affecting the Initial Adhesion and Retention of the Plant Pathogen Xylella fastidiosa in the Foregut of an Insect Vector

2013 ◽  
Vol 80 (1) ◽  
pp. 420-426 ◽  
Author(s):  
Nabil Killiny ◽  
Rodrigo P. P. Almeida
Keyword(s):  
Galacturonic Acid ◽  
Artificial Diet ◽  
Plant Pathogens ◽  
Xylella Fastidiosa ◽  
Insect Vector ◽  
Vector Transmission ◽  
Content Type ◽  
Factors Affecting ◽  
Regulatory Systems ◽  
Initial Adhesion

ABSTRACTVector transmission of bacterial plant pathogens involves three steps: pathogen acquisition from an infected host, retention within the vector, and inoculation of cells into susceptible tissue of an uninfected plant. In this study, a combination of plant and artificial diet systems were used to determine the importance of several genes on the initial adhesion and retention of the bacteriumXylella fastidiosato an efficient insect vector. Mutant strains included fimbrial (fimAandpilB) and afimbrial (hxfAandhxfB) adhesins and three loci involved in regulatory systems (rpfF,rpfC, andcgsA). Transmission assays with variable retention time indicated that HxfA and HxfB were primarily important for early adhesion to vectors, while FimA was necessary for both adhesion and retention. The long pilus protein PilB was not deficient in initial adhesion but may be important for retention. Genes upregulated under the control ofrpfFare important for both initial adhesion and retention, as transmission rates of this mutant strain were initially low and decreased over time, while disruption ofrpfCandcgsAyielded trends similar to that shown by the wild-type control. Because induction of anX. fastidiosatransmissible state requires pectin, a series of experiments were used to test the roles of a polygalacturonase (pglA) and the pectin and galacturonic acid carbohydrates on the transmission ofX. fastidiosa. Results show that galacturonic acid, or PglA activity breaking pectin into its major subunit (galacturonic acid), is required forX. fastidiosavector transmission using an artificial diet system. This study shows that early adhesion and retention ofX. fastidiosaare mediated by different factors. It also illustrates that the interpretation of results of vector transmission experiments, in the context of vector-pathogen interaction studies, is highly dependent on experimental design.

scholarly journals O Antigen Modulates Insect Vector Acquisition of the Bacterial Plant Pathogen Xylella fastidiosa

2015 ◽  
Vol 81 (23) ◽  
pp. 8145-8154 ◽  
Author(s):  
Jeannette N. Rapicavoli ◽  
Nichola Kinsinger ◽  
Thomas M. Perring ◽  
Elaine A. Backus ◽  
Holly J. Shugart ◽  
...  
Keyword(s):  
Cell Surface ◽  
Plant Pathogen ◽  
Pathogenic Bacteria ◽  
Plant Pathogens ◽  
Xylella Fastidiosa ◽  
Insect Vector ◽  
Physiochemical Properties ◽  
Content Type ◽  
O Antigen ◽  
Bacterial Plant Pathogen

ABSTRACTHemipteran insect vectors transmit the majority of plant pathogens. Acquisition of pathogenic bacteria by these piercing/sucking insects requires intimate associations between the bacterial cells and insect surfaces. Lipopolysaccharide (LPS) is the predominant macromolecule displayed on the cell surface of Gram-negative bacteria and thus mediates bacterial interactions with the environment and potential hosts. We hypothesized that bacterial cell surface properties mediated by LPS would be important in modulating vector-pathogen interactions required for acquisition of the bacterial plant pathogenXylella fastidiosa, the causative agent of Pierce's disease of grapevines. Utilizing a mutant that produces truncated O antigen (the terminal portion of the LPS molecule), we present results that link this LPS structural alteration to a significant decrease in the attachment ofX. fastidiosato blue-green sharpshooter foreguts. Scanning electron microscopy confirmed that this defect in initial attachment compromised subsequent biofilm formation within vector foreguts, thus impairing pathogen acquisition. We also establish a relationship between O antigen truncation and significant changes in the physiochemical properties of the cell, which in turn affect the dynamics ofX. fastidiosaadhesion to the vector foregut. Lastly, we couple measurements of the physiochemical properties of the cell with hydrodynamic fluid shear rates to produce a Comsol model that predicts primary areas of bacterial colonization within blue-green sharpshooter foreguts, and we present experimental data that support the model. These results demonstrate that, in addition to reported protein adhesin-ligand interactions, O antigen is crucial for vector-pathogen interactions, specifically in the acquisition of this destructive agricultural pathogen.

scholarly journals Variable Membrane Protein A of Flavescence Dorée Phytoplasma Binds the Midgut Perimicrovillar Membrane ofEuscelidius variegatusand Promotes Adhesion to Its Epithelial Cells

2018 ◽  
Vol 84 (8) ◽  
pp. e02487-17 ◽  
Author(s):  
Nathalie Arricau-Bouvery ◽  
Sybille Duret ◽  
Marie-Pierre Dubrana ◽  
Brigitte Batailler ◽  
Delphine Desqué ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Salivary Glands ◽  
Plant Pathogens ◽  
Insect Cells ◽  
Wild Plants ◽  
Insect Vector ◽  
Plant Host ◽  
Content Type ◽  
Flavescence Dorée ◽  
Fluorescent Beads

ABSTRACTPhytoplasmas are uncultivated plant pathogens and cell wall-less bacteria and are transmitted from plant to plant by hemipteran insects. The phytoplasma's circulative propagative cycle in insects requires the crossing of the midgut and salivary glands, and primary adhesion to cells is an initial step toward the invasion process. The flavescence dorée (FD) phytoplasma possesses a set of variable membrane proteins (Vmps) exposed on its surface, and this pathogen is suspected to interact with insect cells. The results showed that VmpA is expressed by the flavescence dorée phytoplasma present in the midgut and salivary glands. Phytoplasmas cannot be cultivated at present, and no mutant can be produced to investigate the putative role of Vmps in the adhesion of phytoplasma to insect cells. To overcome this difficulty, we engineered theSpiroplasma citrimutant G/6, which lacks the ScARP adhesins, for VmpA expression and used VmpA-coated fluorescent beads to determine if VmpA acts as an adhesin inex vivoadhesion assays andin vivoingestion assays. VmpA specifically interacted withEuscelidiusvariegatusinsect cells in culture and promoted the retention of VmpA-coated beads to the midgut ofE. variegatus. In this latest case, VmpA-coated fluorescent beads were localized and embedded in the perimicrovillar membrane of the insect midgut. Thus, VmpA functions as an adhesin that could be essential in the colonization of the insect by the FD phytoplasmas.IMPORTANCEPhytoplasmas infect a wide variety of plants, ranging from wild plants to cultivated species, and are transmitted by different leafhoppers, planthoppers, and psyllids. The specificity of the phytoplasma-insect vector interaction has a major impact on the phytoplasma plant host range. As entry into insect cells is an obligate process for phytoplasma transmission, the bacterial adhesion to insect cells is a key step. Thus, studying surface-exposed proteins of phytoplasma will help to identify the adhesins implicated in the specific recognition of insect vectors. In this study, it is shown that the membrane protein VmpA of the flavescence dorée (FD) phytoplasma acts as an adhesin that is able to interact with cells ofEuscelidiusvariegatus, the experimental vector of the FD phytoplasma.

scholarly journals Semi-Automatic Method for Early Detection of Xylella fastidiosa in Olive Trees Using UAV Multispectral Imagery and Geostatistical-Discriminant Analysis

2020 ◽  
Vol 13 (1) ◽  
pp. 14
Author(s):  
Annamaria Castrignanò ◽  
Antonella Belmonte ◽  
Ilaria Antelmi ◽  
Ruggiero Quarto ◽  
Francesco Quarto ◽  
...  
Keyword(s):  
Discriminant Analysis ◽  
Early Detection ◽  
Plant Pathogens ◽  
Early Stage ◽  
Xylella Fastidiosa ◽  
Mediterranean Countries ◽  
Parametric Classification ◽  
Aerial Vehicle ◽  
Olive Groves ◽  
Olive Trees

Xylella fastidiosa subsp. pauca (Xfp) is one of the most dangerous plant pathogens in the world. Identified in 2013 in olive trees in south–eastern Italy, it is spreading to the Mediterranean countries. The bacterium is transmitted by insects that feed on sap, and causes rapid wilting in olive trees. The paper explores the use of Unmanned Aerial Vehicle (UAV) in combination with a multispectral radiometer for early detection of infection. The study was carried out in three olive groves in the Apulia region (Italy) and involved four drone flights from 2017 to 2019. To classify Xfp severity level in olive trees at an early stage, a combined method of geostatistics and discriminant analysis was implemented. The results of cross-validation for the non-parametric classification method were of overall accuracy = 0.69, mean error rate = 0.31, and for the early detection class of accuracy 0.77 and misclassification probability 0.23. The results are promising and encourage the application of UAV technology for the early detection of Xfp infection.

scholarly journals Skipping the Insect Vector: Plant Stolon Transmission of the Phytopathogen ‘Ca. Phlomobacter fragariae’ from the Arsenophonus Clade of Insect Endosymbionts

Insects ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 93
Author(s):  
Jessica Dittmer ◽  
Thierry Lusseau ◽  
Xavier Foissac ◽  
Franco Faoro
Keyword(s):  
Plant Pathogens ◽  
Model Systems ◽  
Insect Vector ◽  
Evolutionary Perspective ◽  
Evolutionary Transition ◽  
Strawberry Plant ◽  
Disease Symptoms ◽  
Transmission Electron ◽  
Nutrient Provisioning ◽  
Early Growth Phase

The genus Arsenophonus represents one of the most widespread clades of insect endosymbionts, including reproductive manipulators and bacteriocyte-associated primary endosymbionts. Two strains belonging to the Arsenophonus clade have been identified as insect-vectored plant pathogens of strawberry and sugar beet. The bacteria accumulate in the phloem of infected plants, ultimately causing leaf yellows and necrosis. These symbionts therefore represent excellent model systems to investigate the evolutionary transition from a purely insect-associated endosymbiont towards an insect-vectored phytopathogen. Using quantitative PCR and transmission electron microscopy, we demonstrate that ‘Candidatus Phlomobacter fragariae’, bacterial symbiont of the planthopper Cixius wagneri and the causative agent of Strawberry Marginal Chlorosis disease, can be transmitted from an infected strawberry plant to multiple daughter plants through stolons. Stolons are horizontally growing stems enabling the nutrient provisioning of daughter plants during their early growth phase. Our results show that Phlomobacter was abundant in the phloem sieve elements of stolons and was efficiently transmitted to daughter plants, which rapidly developed disease symptoms. From an evolutionary perspective, Phlomobacter is, therefore, not only able to survive within the plant after transmission by the insect vector, but can even be transmitted to new plant generations, independently from its ancestral insect host.

scholarly journals Understanding employee turnover in humanitarian organizations

2016 ◽  
Vol 48 (4) ◽  
pp. 208-214 ◽  
Author(s):  
Rameshwar Dubey ◽  
Angappa Gunasekaran ◽  
Nezih Altay ◽  
Stephen J Childe ◽  
Thanos Papadopoulos
Keyword(s):  
Employee Turnover ◽  
Factor Loading ◽  
Personal Factors ◽  
Related Factors ◽  
Content Type ◽  
Factors Affecting ◽  
Work Related ◽  
Humanitarian Organizations ◽  
Using Data ◽  
High Level

Purpose – At a time when the number and seriousness of disasters seems to be increasing, humanitarian organizations find that besides their challenging work they are faced with problems caused by a high level of turnover of staff. The paper aims to discuss these issues. Design/methodology/approach – Based on the 24 variables leading to employee turnover identified by Cotton and Tuttle (1986) the authors analyse the work-related, external and personal factors affecting employee turnover in humanitarian organizations, using a survey of members of the Indian National Institute of Disaster Management. Findings – Results indicated that the three factors are present. Of the external factors, only employment perception had a factor loading over 0.7; of the work-related factors, all were significant; of the personal factors, biographical information, marital status, number of dependants, aptitude and ability and intelligence had the highest loadings. It was also shown that behavioural intentions and net expectation were not significant. Originality/value – Only a few studies reported on employee turnover and its reasons are not well understood in the context of humanitarian organizations. To address this need, the aim of this paper is to explore the personal reasons impacting employee turnover in humanitarian organizations. In the study the authors have adopted 24 variables used in Cotton and Tuttle (1986) and classified into constructs to explain turnover, and further tested the model using data gathered from humanitarian organizations.

scholarly journals Understanding consumer loyalty to technology-based self-services with credence qualities

2015 ◽  
Vol 29 (6/7) ◽  
pp. 522-532 ◽  
Author(s):  
Lisa Schuster ◽  
Judy Proudfoot ◽  
Judy Drennan
Keyword(s):  
Professional Services ◽  
Content Type ◽  
Consumer Responses ◽  
Factors Affecting ◽  
Behavioral Loyalty ◽  
Behavioral Domain ◽  
Continued Use ◽  
Self Service ◽  
The Impact ◽  
Goal Directed Behavior

Purpose – This paper aims to use the Model of Goal-Directed Behavior (MGB) to examine the factors affecting consumers’ continued use of emerging technology-based self-services (TBSSs) with credence qualities. Professional services, which traditionally require specialized knowledge and high levels of interpersonal interaction to produce owing to their credence qualities, are increasingly delivered via self-service technologies. Health services delivered via mobile devices, for example, facilitate self-care without direct involvement from health professionals. Design/methodology/approach – A mental health service delivered via the Internet and mobile phone, myCompass, was selected as the research context. Twenty interviews were conducted with users of myCompass and the data were thematically analyzed. Findings – The findings of the study showcase the unique determinants of consumers’ continued use of TBSSs with credence qualities relative to the more routine services which have been the focus of extant research. The findings further provide support for the utility of the MGB in explaining service continuance, although the importance of distinguishing between extrinsic and intrinsic motivational components of behavioral desire and capturing the impact of social influence beyond subjective norms is also highlighted. Originality/value – This study contributes to recent research examining differences in consumer responses across TBSSs and behavioral loyalty to these services. It also provides empirical evidence for broadening and deepening the MGB within this behavioral domain.

Quality of life in breast cancer sufferers

2016 ◽  
Vol 29 (7) ◽  
pp. 721-732 ◽  
Author(s):  
Ahmed Essmat Shouman ◽  
Nahla Fawzy Abou El Ezz ◽  
Nivine Gado ◽  
Amal Mahmoud Ibrahim Goda
Keyword(s):  
Breast Cancer ◽  
Quality Of Life ◽  
Family Income ◽  
Early Stage ◽  
Functional Domain ◽  
Related Factors ◽  
Specific Patient ◽  
Content Type ◽  
Factors Affecting

Purpose – The purpose of this paper is to measure health-related quality of life (QOL) among patients with early stage cancer breast under curative treatment at department of oncology and nuclear medicine at Ain Shams University Hospitals. Identify factors affecting QOL among these patients. Design/methodology/approach – A cross-sectional study measured QOL among early stage female breast cancer (BC) patients and determined the main factors affecting their QOL. Three interviewer administered questionnaires were used. Findings – The physical domain mostly affected in BC patients and the functional domain least. Socio-demographic factors that significantly affected BC patients QOL scores were patient age, education, having children and family income. Specific patient characteristics include caregiver presence – a factor that affected different QOL scores. Age at diagnosis, affection in the side of the predominant hand, post-operative chemotherapy and difficulty in obtaining the medication were the disease-related factors that affected QOL scores. Originality/value – The final model predicting QOL for early stage female BC patients included age, education and difficulty in obtaining the medication as determinants for total QOL score. Carer presence was the specific patient characteristic that affected different QOL scores.

Factors affecting coagulation: fibrinolysis in chronic subdural fluid collections

1983 ◽  
Vol 58 (2) ◽  
pp. 242-245 ◽  
Author(s):  
Bryce Weir ◽  
Philip Gordon
Keyword(s):  
Degradation Products ◽  
Hemoglobin Content ◽  
Fibrin Degradation Product ◽  
Content Type ◽  
Factors Affecting ◽  
Fibrin Degradation Products ◽  
Subdural Hematomas ◽  
Increased Risk ◽  
Fluid Collections ◽  
Fine Print

✓ Plasminogen, alpha2-antiplasmin, fibrinogen, fibrin degradation products (FDP's), and hemoglobin were measured in the supernatant fluid of 25 chronic subdural hematomas and five chronic subdural hygromas. The 30 patients underwent pre- and postoperative computerized tomography. The hematomas were characterized by low fibrinogen and high fibrin degradation product concentrations. The hemoglobin content varied directly with the alpha2-antiplasmin, and inversely with the plasminogen. Four patients underwent reoperation for recurrences. The initial fluid from these cases was characterized by relatively high plasminogen and low alpha2-antiplasmin. The hygromas had no hemoglobin, and low fibrinogen, high FDP's, low alpha2-antiplasmin, and variable plasminogen levels. It is possible that those cases having the greatest capacity to produce plasmin (high plasminogen and low alpha2-antiplasmin) can produce more FDP's which in turn causes more rebleeding and an increased risk of reaccumulation of chronic subdural hematomas.

Increasing revenue and attendance in Canadian Baptist churches

2015 ◽  
Vol 42 (12) ◽  
pp. 1071-1089
Author(s):  
Alan Chan ◽  
Bruce G. Fawcett ◽  
Shu-Kam Lee
Keyword(s):  
Church Health ◽  
Eastern Canada ◽  
Data Set ◽  
Content Type ◽  
Factors Affecting ◽  
Scarce Resources ◽  
Baptist Churches ◽  
And Performance ◽  
The Impact ◽  
Simulation Exercises

Purpose – Church giving and attendance are two important indicators of church health and performance. In the literature, they are usually understood to be simultaneously determined. The purpose of this paper is to estimate if there a sustainable church congregation size using Wintrobe’s (1998) dictatorship model. The authors want to examine the impact of youth and adult ministry as well. Design/methodology/approach – Using the data collected from among Canadian Baptist churches in Eastern Canada, this study investigates the factors affecting the level of the two indicators by the panel-instrumental variable technique. Applying Wintrobe’s (1998) political economy model on dictatorship, the equilibrium level of worship attendance and giving is predicted. Findings – Through various simulation exercises, the actual church congregation sizes is approximately 50 percent of the predicted value, implying inefficiency and misallocation of church resources. The paper concludes with insights on effective ways church leaders can allocate scarce resources to promote growth within churches. Originality/value – The authors are the only researchers getting the permission from the Atlantic Canada Baptist Convention to use their mega data set on church giving and congregation sizes as per the authors’ knowledge. The authors are also applying a theoretical model on dictatorship to religious/not for profits organizations.

Policy and institutions facilitating entrepreneurial spin-offs: USA, Asia and Europe

2014 ◽  
Vol 3 (2) ◽  
pp. 186-196 ◽  
Author(s):  
Rosa Caiazza ◽  
David Audretsch ◽  
Tiziana Volpe ◽  
Julie Debra Singer
Keyword(s):  
Institutional Setting ◽  
Policy Debate ◽  
Content Type ◽  
Factors Affecting ◽  
Institutional Settings ◽  
The Usa ◽  
New Perspective ◽  
National Analysis ◽  
The Impact ◽  
Cross National

Purpose – Existing work documents the role that institutional setting plays in the process of spin-off creation. However, despite decades of studies, scholars have not clearly explained why some regions are more involved in spin-off activity than others. Drawing from institutional theory, the purpose of this paper is to compare different institutional settings identifying factors affecting the general environment capability to support spin-off activity of a specific region. Design/methodology/approach – The authors utilize a cross-national analysis of American, Asian, and European areas identifying factors affecting their different rate of spin-off activity. This study contributes to the policy debate concerning entrepreneurship and how best to spur spin-off activities. Findings – In this paper, the authors identify the general and specific factors that explain the cross-national diversity in spin-off creation. The authors then perform an analysis of the impact of these factors in various regions of the USA, Asia, and Europe, providing evidence for the necessity of specific combinations of these factors. Originality/value – The paper offers a new perspective on the causes of spin-offs through a cross-national analysis of many areas around the world.

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