When a Palearctic bacterium meets a Nearctic insect vector: Genetic and ecological insights into the emergence of the grapevine Flavescence dorée epidemics in Europe

Insect vectors transmit viruses and bacteria that can cause severe diseases in plants and economic losses due to a decrease in crop production. Insect vectors, like all other organisms, are colonized by a community of various microorganisms, which can influence their physiology, ecology, evolution, and also their competence as vectors. The important ecological meaning of bacteriophages in various ecosystems and their role in microbial communities has emerged in the past decade. However, only a few phages have been described so far in insect microbiomes. The leafhopper Euscelidius variegatus is a laboratory vector of the phytoplasma causing Flavescence dorée, a severe grapevine disease that threatens viticulture in Europe. Here, the presence of a temperate bacteriophage in E. variegatus (named Euscelidius variegatus phage 1, EVP-1) was revealed through both insect transcriptome analyses and electron microscopic observations. The bacterial host was isolated in axenic culture and identified as the bacterial endosymbiont of E. variegatus (BEV), recently assigned to the genus Candidatus Symbiopectobacterium. BEV harbors multiple prophages that become active in culture, suggesting that different environments can trigger different mechanisms, finely regulating the interactions among phages. Understanding the complex relationships within insect vector microbiomes may help in revealing possible microbe influences on pathogen transmission, and it is a crucial step toward innovative sustainable strategies for disease management in agriculture.

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Genetic diversity of European phytoplasmas of the 16SrV taxonomic group and proposal of ‘Candidatus Phytoplasma rubi’

INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY ◽

10.1099/ijs.0.025411-0 ◽

2011 ◽

Vol 61 (9) ◽

pp. 2129-2134 ◽

Cited By ~ 65

Author(s):

Sylvie Malembic-Maher ◽

Pascal Salar ◽

Luisa Filippin ◽

Patricia Carle ◽

Elisa Angelini ◽

...

Keyword(s):

16S Rrna ◽

16S Rrna Gene ◽

Sequence Similarity ◽

Housekeeping Genes ◽

Taxonomic Group ◽

Rrna Gene ◽

Insect Vector ◽

Flavescence Dorée ◽

The 16S Rrna Gene ◽

Specific Sequences

In addition to the grapevine flavescence dorée phytoplasmas, other members of taxonomic group 16SrV phytoplasmas infect grapevines, alders and species of the genera Clematis and Rubus in Europe. In order to investigate which phytoplasmas constitute discrete, species-level taxa, several strains were analysed by comparing their 16S rRNA gene sequences and a set of five housekeeping genes. Whereas 16S rRNA gene sequence similarity values were >97.5 %, the proposed threshold to distinguish two ‘Candidatus Phytoplasma’ taxa, phylogenetic analysis of the combined sequences of the tuf, rplV-rpsC, rplF-rplR, map and uvrB-degV genetic loci showed that two discrete phylogenetic clusters could be clearly distinguished. The first cluster grouped flavescence dorée (FD) phytoplasmas, alder yellows (AldY) phytoplasmas, Clematis (CL) phytoplasmas and the Palatinate grapevine yellows (PGY) phytoplasmas. The second cluster comprised Rubus stunt (RS) phytoplasmas. In addition to the specificity of the insect vector, the Rubus stunt phytoplasma contained specific sequences in the 16S rRNA gene. Hence, the Rubus stunt phytoplasma 16S rRNA gene was sufficiently differentiated to represent a novel putative taxon: ‘Candidatus Phytoplasma rubi’.

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

Applied and Environmental Microbiology ◽

10.1128/aem.02487-17 ◽

2018 ◽

Vol 84 (8) ◽

pp. e02487-17 ◽

Cited By ~ 11

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.

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New Viral Sequences Identified in the Flavescence Dorée Phytoplasma Vector Scaphoideus titanus

Viruses ◽

10.3390/v12030287 ◽

2020 ◽

Vol 12 (3) ◽

pp. 287

Author(s):

Sara Ottati ◽

Marco Chiapello ◽

Luciana Galetto ◽

Domenico Bosco ◽

Cristina Marzachì ◽

...

Keyword(s):

Large Scale ◽

Control Measures ◽

Insect Vector ◽

Wine Production ◽

Flavescence Dorée ◽

Reverse Transcription Pcr ◽

Scaphoideus Titanus ◽

The Usa ◽

In The Wild ◽

Increasing Demand

(1) Background: The leafhopper Scaphoideus titanus is the primary vector of Flavescence dorée phytoplasma (FDp) in European vineyards. Flavescence dorée is one of the most severely damaging diseases of Vitis vinifera and, consequently, a major threat to grape and wine production in several European countries. Control measures are compulsory, but they mainly involve large-scale insecticide treatments, with detrimental impacts on the environment. One possible solution is to exploit the largely unexplored genetic diversity of viruses infecting S. titanus as highly specific and environmentally benign tools for biological control. (2) Methods: A metatranscriptomic approach was adopted to identify viruses that may infect individuals caught in the wild in both its native (United States) and invasive (Europe) areas. Reverse transcription PCR was used to confirm their presence in RNA pools and explore their prevalence. (3) Results: We described nine new RNA viruses, including members of “Picorna-Calici”, “Permutotetra”, “Bunya-Arena”, “Reo”, “Partiti-Picobirna”, “Luteo-Sobemo” and “Toti-Chryso” clades. A marked difference in the diversity and abundance of the viral species was observed between the USA population and the European ones. (4) Conclusions: This work represents the first survey to assess the viral community of a phytoplasma insect vector. The possibility to exploit these naturally occurring viruses as specific and targeted biocontrol agents of S. titanus could be the answer to increasing demand for a more sustainable viticulture.

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Interactions between the flavescence dorée phytoplasma and its insect vector indicate lectin-type adhesion mediated by the adhesin VmpA

Scientific Reports ◽

10.1038/s41598-021-90809-z ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Nathalie Arricau-Bouvery ◽

Sybille Duret ◽

Marie-Pierre Dubrana ◽

Delphine Desqué ◽

Sandrine Eveillard ◽

...

Keyword(s):

Salivary Glands ◽

Insect Cell ◽

Insect Cell Line ◽

Insect Vector ◽

Flavescence Dorée ◽

Salivary Gland Cells ◽

Scaphoideus Titanus ◽

Euscelidius Variegatus ◽

Natural Vector ◽

Insect Gut

AbstractThe flavescence dorée phytoplasma undergoes a propagative cycle in its insect vectors by first interacting with the insect cell surfaces, primarily in the midgut lumen and subsequently in the salivary glands. Adhesion of flavescence dorée phytoplasma to insect cells is mediated by the adhesin VmpA. We hypothesize that VmpA may have lectin-like activity, similar to several adhesins of bacteria that invade the insect gut. We first demonstrated that the luminal surface of the midgut and the basal surface of the salivary gland cells of the natural vector Scaphoideus titanus and those of the experimental vector Euscelidius variegatus were differentially glycosylated. Using ELISA, inhibition and competitive adhesion assays, and protein overlay assays in the Euva-6 insect cell line, we showed that the protein VmpA binds insect proteins in a lectin-like manner. In conclusion, the results of this study indicate that N-acetylglucosamine and mannose present on the surfaces of the midgut and salivary glands serve as recognition sites for the phytoplasma adhesin VmpA.

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A scanning electron microscopic study of the eggs of Culicoides variipennis (Diptera: Ceratopogonidae)

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100128705 ◽

1987 ◽

Vol 45 ◽

pp. 884-885 ◽

Cited By ~ 1

Author(s):

R. A. Nunamaker ◽

C. E. Nunamaker ◽

B. C. Wick

Keyword(s):

Distinct Species ◽

Hemorrhagic Disease ◽

Insect Vector ◽

Electron Microscopic ◽

Important Species ◽

Scanning Electron Microscopic Study ◽

Laboratory Colony ◽

Culicoides Variipennis ◽

Morphological Differences ◽

Scanning Electron

Culicoides variipennis (Coquillett) is probably the most economically important species of biting midge in the U.S. due to its involvement in the transmission of bluetongue (BT) disease of sheep, cattle and ruminant wildlife, and epizootic hemorrhagic disease (EHD) of deer. Proposals have been made to recognize the eastern and western populations of this insect vector as distinct species. Others recommend use of the term “variipennis complex” until such time that the necessary biosystematic studies have been made to determine the genetic nature and/or minute morphological differences within the population structure over the entire geographic range of the species. Increasingly, students of ootaxonomy are relying on scanning electron microscopy (SEM) to assess chorionic features. This study was undertaken to provide comparative chorionic data for the C. variipennis complex.Culicoides variipennis eggs were collected from a laboratory colony maintained in Laramie, Wyoming.

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Scent Sensors Are New Target for Repellents To Curb Insect Vector-Borne Diseases

Microbe Magazine ◽

10.1128/microbe.4.312.1 ◽

2009 ◽

Vol 4 (7) ◽

pp. 312-312

Keyword(s):

Insect Vector ◽

Vector Borne Diseases ◽

Vector Borne

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Metabolic reprogramming during the Trypanosoma brucei life cycle

F1000Research ◽

10.12688/f1000research.10342.2 ◽

2017 ◽

Vol 6 ◽

pp. 683 ◽

Cited By ~ 31

Author(s):

Terry K. Smith ◽

Frédéric Bringaud ◽

Derek P. Nolan ◽

Luisa M. Figueiredo

Keyword(s):

Life Cycle ◽

Trypanosoma Brucei ◽

Model Organism ◽

Protozoan Parasite ◽

Tsetse Fly ◽

Metabolic Reprogramming ◽

Mammalian Host ◽

Insect Vector ◽

Environmental Signals ◽

Cellular Metabolic Activity

Cellular metabolic activity is a highly complex, dynamic, regulated process that is influenced by numerous factors, including extracellular environmental signals, nutrient availability and the physiological and developmental status of the cell. The causative agent of sleeping sickness, Trypanosoma brucei, is an exclusively extracellular protozoan parasite that encounters very different extracellular environments during its life cycle within the mammalian host and tsetse fly insect vector. In order to meet these challenges, there are significant alterations in the major energetic and metabolic pathways of these highly adaptable parasites. This review highlights some of these metabolic changes in this early divergent eukaryotic model organism.

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Sequential production of gametes during meiosis in trypanosomes

Communications Biology ◽

10.1038/s42003-021-02058-5 ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Lori Peacock ◽

Chris Kay ◽

Chloe Farren ◽

Mick Bailey ◽

Mark Carrington ◽

...

Keyword(s):

Salivary Glands ◽

Nuclear Dna ◽

Nuclear Dna Content ◽

Cell Types ◽

Tsetse Fly ◽

Binucleate Cell ◽

Insect Vector ◽

Content Ratio ◽

Different Cell Types ◽

Meiosis I

AbstractMeiosis is a core feature of eukaryotes that occurs in all major groups, including the early diverging excavates. In this group, meiosis and production of haploid gametes have been described in the pathogenic protist, Trypanosoma brucei, and mating occurs in the salivary glands of the insect vector, the tsetse fly. Here, we searched for intermediate meiotic stages among trypanosomes from tsetse salivary glands. Many different cell types were recovered, including trypanosomes in Meiosis I and gametes. Significantly, we found trypanosomes containing three nuclei with a 1:2:1 ratio of DNA contents. Some of these cells were undergoing cytokinesis, yielding a mononucleate gamete and a binucleate cell with a nuclear DNA content ratio of 1:2. This cell subsequently produced three more gametes in two further rounds of division. Expression of the cell fusion protein HAP2 (GCS1) was not confined to gametes, but also extended to meiotic intermediates. We propose a model whereby the two nuclei resulting from Meiosis I undergo asynchronous Meiosis II divisions with sequential production of haploid gametes.

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