Vector Transmission of a Plant-Pathogenic Bacterium in the Arsenophonus Clade Sharing Ecological Traits with Facultative Insect Endosymbionts

The planthopper Pentastiridius leporinus (Hemiptera: Cixiidae) is the major vector of a nonculturable plant-pathogenic γ-3 proteobacterium associated with a disease of sugar beet called syndrome “basses richesses” (SBR). The bacterium, here called SBR bacterium, belongs to the Arsenophonous clade, which includes mostly insect-associated facultative symbionts. Assays using field-collected planthopper nymphs and adults were carried out to investigate the interaction of SBR bacterium with the insect vector and its transmission to sugar beet. Field-collected planthoppers showed a percentage of infection that averaged from 57% for early instar nymphs to near 100% for late instar nymphs and emerging adults. SBR bacterium was persistently transmitted by emerging adults. Root-feeding nymphs were able to inoculate SBR bacterium to sugar beet. The bacterium was transmitted vertically from infected parental females to their respective offspring with an average frequency of 30%. Real-time polymerase chain reaction assays on dissected planthopper internal organs revealed a high concentration of the bacterium within male and female reproductive organs and within female salivary glands. SBR-like bacteria were observed through transmission electron microscopy in the cytoplasm of different insect organs including ovaries, salivary glands, and guts with no evidence for cytological disorders. SBR bacterium seems to share common ecological traits of insect-transmitted plant pathogens and facultative insect endosymbionts suggesting it may have evolved primarily as an insect-associated bacterium.

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

Insects ◽

10.3390/insects12020093 ◽

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.

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Some notes on the relationship of plant viruses with vector and non-vector insects

Parasitology ◽

10.1017/s003118200002429x ◽

1941 ◽

Vol 33 (1) ◽

pp. 110-116 ◽

Cited By ~ 14

Author(s):

Kenneth M. Smith

Keyword(s):

Sugar Beet ◽

Experimental Evidence ◽

Plant Viruses ◽

Artificial Feeding ◽

The Body ◽

The Other ◽

Insect Vector ◽

Feeding Methods ◽

Relationship Of ◽

The Relationship

Extracts of caterpillars and other insects are shown to inhibit the infective power of tobacco mosaic and tobacco necrosis viruses. The inhibitor is not sedimented after spinning for 2½ hr. at 30,000 r.p.m. Experiments with non-vector insects such as caterpillars have shown that the virus of sugar-beet curly-top, of tobacco ringspot and other viruses, are destroyed within the body of the insect. On the other hand, tobacco mosaic virus passes through the body of the caterpillar unchanged though greatly reduced in concentration. By the use of the specific insect vector and artificial feeding methods it was possible to recover the virus of curly-top 24 hr. after it had been injected into the blood of the caterpillar but the viruses of tobacco mosaic and tobacco necrosis could not be so recovered. Experimental evidence is given to show that the virus of beet curly-top is present in the saliva of viruliferous insects.

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Chewing behaviour of Holstein steers fed diets containing different levels of non-forage fibre in a low forage diet

Proceedings of the British Society of Animal Science ◽

10.1017/s1752756200030003 ◽

2009 ◽

Vol 2009 ◽

pp. 161-161

Author(s):

M Mojtahedi ◽

M Danesh Mesgaran ◽

A Heravi Moussavi ◽

A Tahmasbi

Keyword(s):

Sugar Beet ◽

Barley Grain ◽

Sugar Beet Pulp ◽

Soluble Fiber ◽

High Concentration ◽

Beet Pulp ◽

Feeding Value ◽

Lactating Dairy Cattle ◽

Chewing Behaviour

Sugar beet pulp (SBP) is fed to ruminants as a non-forage ﬁbre source (NFFS) ingredient. Early work by Ronning and Bath (1962) demonstrated that SBP was similar in feeding value to barley grain for lactating dairy cattle, supporting classiﬁcation of beet pulp as an energy concentrate. Sugar beet pulp contains approximately 40% neutral detergent ﬁbre (NDF) and is unique in its high concentration of neutral detergent soluble ﬁber, especially pectic substances (~25% of dry matter (DM)). However, the effects of SBP when substituted with different feed sources in ration are variable that depend on chemical composition, types and physical characteristics. The time which cows spent eating and ruminating (total chewing time) is a measure of the physically effective fibre value of a feed. The objective of the present experiment was to evaluate the effect of substitution of barley grain with SBP as a NFFS on chewing activity of Holstein steers.

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Asian citrus psyllid adults inoculate huanglongbing bacterium more efficiently than nymphs when this bacterium is acquired by early instar nymphs

Scientific Reports ◽

10.1038/s41598-020-75249-5 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

El-Desouky Ammar ◽

Justin George ◽

Kasie Sturgeon ◽

Lukasz L. Stelinski ◽

Robert G. Shatters

Keyword(s):

Latent Period ◽

Salivary Glands ◽

Emerging Adults ◽

Citrus Greening ◽

Asian Citrus Psyllid ◽

Diaphorina Citri ◽

Citrus Greening Disease ◽

Early Instar ◽

Liberibacter Asiaticus ◽

Greening Disease

Abstract The Asian citrus psyllid (Diaphorina citri) transmits the bacterium ‘Candidatus Liberibacter asiaticus’ (CLas), which causes huanglongbing (citrus greening) disease, in a circulative-propagative manner. We compared CLas inoculation efficiency of D. citri nymphs and adults into healthy (uninfected) citron leaves when both vector stages were reared from eggs on infected plants. The proportion of CLas-positive leaves was 2.5% for nymphs and 36.3% for adults. CLas acquisition by early instar nymphs followed by dissections of adults and 4th instar nymphs revealed that CLas bacterium had moved into the head-thorax section (containing the salivary glands) in 26.7–30.0% of nymphs and 37–45% of adults. Mean Ct values in these sections were 31.6–32.9 and 26.8–27.0 for nymphs and adults, respectively. Therefore, CLas incidence and titer were higher in the head-thorax of adults than in nymphs. Our results suggest that following acquisition of CLas by early instar D. citri nymphs, emerging adults inoculate the bacteria into citrus more efficiently than nymphs because adults are afforded a longer latent period necessary for multiplication and/or translocation of CLas into the salivary glands of the vector. We propose that CLas uses D. citri nymphs mainly for pathogen acquisition and multiplication, and their adults mainly for pathogen inoculation and spread.

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A plant DNA virus replicates in the salivary glands of its insect vector via recruitment of host DNA synthesis machinery

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1820132117 ◽

2020 ◽

Vol 117 (29) ◽

pp. 16928-16937 ◽

Cited By ~ 8

Author(s):

Ya-Zhou He ◽

Yu-Meng Wang ◽

Tian-Yan Yin ◽

Elvira Fiallo-Olivé ◽

Yin-Quan Liu ◽

...

Keyword(s):

Dna Synthesis ◽

Salivary Glands ◽

Large Family ◽

Plant Viruses ◽

Nuclear Antigen ◽

Insect Vector ◽

Dna Virus ◽

Dna Viruses ◽

Plant Dna ◽

Leaf Curl

Whereas most of the arthropod-borne animal viruses replicate in their vectors, this is less common for plant viruses. So far, only some plant RNA viruses have been demonstrated to replicate in insect vectors and plant hosts. How plant viruses evolved to replicate in the animal kingdom remains largely unknown. Geminiviruses comprise a large family of plant-infecting, single-stranded DNA viruses that cause serious crop losses worldwide. Here, we report evidence and insight into the replication of the geminivirus tomato yellow leaf curl virus (TYLCV) in the whitefly (Bemisia tabaci) vector and that replication is mainly in the salivary glands. We found that TYLCV induces DNA synthesis machinery, proliferating cell nuclear antigen (PCNA) and DNA polymerase δ (Polδ), to establish a replication-competent environment in whiteflies. TYLCV replication-associated protein (Rep) interacts with whitefly PCNA, which recruits DNA Polδ for virus replication. In contrast, another geminivirus, papaya leaf curl China virus (PaLCuCNV), does not replicate in the whitefly vector. PaLCuCNV does not induce DNA-synthesis machinery, and the Rep does not interact with whitefly PCNA. Our findings reveal important mechanisms by which a plant DNA virus replicates across the kingdom barrier in an insect and may help to explain the global spread of this devastating pathogen.

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Digital PCR Technology for Detection of Palm-Infecting Phytoplasmas Belonging to Group 16SrIV that Occur in Florida

Plant Disease ◽

10.1094/pdis-06-17-0787-re ◽

2018 ◽

Vol 102 (5) ◽

pp. 1008-1014 ◽

Cited By ~ 12

Author(s):

Brian W. Bahder ◽

Ericka E. Helmick ◽

De-Fen Mou ◽

Nigel A. Harrison ◽

Robert Davis

Keyword(s):

Real Time ◽

Real Time Pcr ◽

Nested Pcr ◽

Plant Pathogens ◽

Rapid Determination ◽

Disease Spread ◽

Taqman Assay ◽

Insect Vector ◽

Palm Trees ◽

Pcr Assays

Phytoplasmas are an economically important group of plant pathogens that negatively impact a wide variety of plants in agricultural and natural ecosystems. In Florida, palm trees are essential elements in the nursery and landscaping industries that suffer from diseases caused by phytoplasmas that are related to each other but are classified in two different subgroups, 16SrIV-A and 16SrIV-D. In this study, a TaqMan assay was developed for digital polymerase chain reaction (dPCR) to detect both palm-infecting phytoplasmas found in Florida. When compared with real-time PCR assays and nested PCR assays, dPCR was capable of detecting the phytoplasmas at much lower concentrations than was possible by using real-time PCR and nested PCR. Additionally, the assay was capable of detecting 16SrIV-B phytoplasma as well as isolates representing the 16SrI and 16SrIII phytoplasma groups. Due to sequence identity of primer annealing regions across diverse phytoplasmas, the assay is likely to be successful for detection of a wide variety of phytoplasmas. The increased sensitivity of this dPCR assay over real-time PCR will allow for earlier detection of phytoplasma infection in palm trees, as well as for screening of salivary glands of candidate insect vector species. These advantages should aid timely management decisions to reduce disease spread and rapid determination of phytoplasma transmission by vectors.

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