Transmission Of Plant Viruses Research Articles

Aphid transmission of Cauliflower mosaic virus

Transmission of plant viruses is the result of interactions between a given virus, the host plant, and the vector. Most research has focused on molecular and cellular virus-vector interactions, and the host has only been regarded as a reservoir from which the virus is acquired by the vector more or less accidentally. However, a growing body of evidence suggests that the host can play a crucial role in transmission. Indeed, at least one virus, Cauliflower mosaic virus, exploits the host's cellular pathways to form specialized intracellular structures that optimize virus uptake by the vector and hence transmission.

Fungal transmission of plant viruses.

Fungal zoospores of Olpidium species transmit several viruses in the family Tombusviridae as well as in the Ophio- and Varicosavirus genera. This unit describes procedures for virus transmission by Olpidium sp. The method is useful for assessing fungal transmissibility of a given virus as well as for further studies on molecular and biological aspects of virus/vector interaction.

The effect of transmission route on plant virus epidemic development and disease control

A model for indirect vector transmission and epidemic development of plant viruses is extended to consider direct transmission through vector mating. A basic reproduction number is derived which is the sum of the R0 values specific for three transmission routes. We analyse the model to determine the effect of direct transmission on plant disease control directed against indirect transmission. Increasing the rate of horizontal sexual transmission means that vector control rate or indirect transmission rate must be increased/decreased substantially to maintain R0 at a value less than 1. By contrast, proportionately increasing the probability of transovarial transmission has little effect. Expressions are derived for the steady-state values of the viruliferous vector population. There is clear advantage for an insect virus in indirect transmission to plants, especially where the sexual and transovarial transmission rates are low; however information on virulence–transmissibility relationships is required to explain the evolution of a plant virus from an insect virus.

Behavioural aspects influencing plant virus transmission by homopteran insects

Homopterans including aphids, whiteflies and leafhoppers are the major vectors of viruses comprising more than 80% of insect-transmitted viruses which represents close to 400 virus species within 39 different genera. Host plant recognition by homopterans requires a series of steps that are linked to plant virus transmission, including host searching or pre-alighting behaviour, probing on superficial tissues, settlement and stylet penetration to the target feeding tissues and salivation and continuous sap ingestion from the preferred feeding site. This review considers how vector behaviour influences the transmission and spread of plant viruses depending on the type of virus-vector relationship. Most studies have concentrated on aphid-transmitted viruses and particular probing and feeding behavioural processes and activities leading to the transmission of cuticula-borne and circulative viruses have been identified. The review also focuses on which are the most likely retention sites within the insect's body of cuticula-borne viruses. Finally, the influences of virus infection on vector behaviour such as changes in the attractiveness, settlement or feeding preference together with changes on vector performance (development, fecundity, rate of population increase and survival) are discussed.

Aphid Transmission of Plant Viruses

A majority of plant viruses are transmitted between hosts by insect vectors, and it is often important to use insect transmission in the laboratory to maintain virus isolates or to study virus-vector-plant interactions. Although many of these viruses can also be mechanically transmitted in the laboratory using infected sap, maintenance by mechanical transmission can often lead to changes in the virus, either minor changes in gene sequences or, in some cases, major deletions of genome sequences. These can affect both virus-vector and virus-host interactions. This unit describes some simple and practical methods for conducting virus transmission experiments using sap-sucking insects.

Behavior of Bird Cherry-Oat Aphid and Green Peach Aphid in Relation to Potato Virus Y Transmission

Potato virus Y is transmitted to potato in a nonpersistent manner by many aphid species, some of which do not colonize this crop. The behavior of bird cherry-oat aphid, Rhopalosiphum padi (L.) on potato, Solanum tuberosum L., a plant species that is not colonized by this aphid, was described and compared with that of the potato-colonizing green peach aphid, Myzuspersicae (Sulzer). A higher proportion of winged morph of R. padi than M. persicae left the plant, but aphids that stayed in contact with the plant took the same mean time to initiate the first probe and it lasted the same mean time compared with M. persicae. Electronic penetration graph technique was used to study the probing behavior of the aphids during Potato virus Y (family Potyviridae, genus Potyvirus, PVY) transmission tests. Transmission rate decreased from 29 to 8% when the acquisition time increased from 5 min of continuous probing to 1 h with M. persicae, but it remained low (2 and 1%) with R. padi. Most of the difference in transmission rate between acquisition time with M. persicae and between aphid species was related to the change in the time and behavior taking place between the last cell puncture of the acquisition phase to the first cell puncture of the inoculation phase. Results presented here clearly demonstrated the importance of host plant selection and probing behavior in the transmission of nonpersistent plant viruses. They also stress the need to consider the behavior of the aphid in the design of laboratory tests of virus vector efficacy.

A key protein for transmission of plant viruses at the tip of the insect vector stylet

Auteur(s) : M Blanc1, M Uzest1, T Candresse2, M Drucker1, A Fereres3, D Gargani1, E Garzo3, E Hebrard4 1UMR BGPI, Inra-Cirad-AgroM, TA A54/K, Campus international de Baillarguet, 34398 Montpellier Cedex 05 2Inra, UMR Genomique, Villenave d’Ornon 3CSIC, CCMA, Madrid, Espagne 4IRD, Montpellier Du fait de l’immobilite de leurs hotes, l’immense majorite des virus de plante utilisent des vecteurs specifiques pour passer d’un hote a un autre. Ces « vehicules de transport » [...]

A key protein for transmission of plant viruses at the tip of the insect vector stylet

A key protein for transmission of plant viruses at the tip of the insect vector stylet

Molecular and morphological evaluation of the aphid genus Hyalopterus Koch (Insecta: Hemiptera: Aphididae), with a description of a new species

Aphids in the genus Hyalopterus Koch (Hemiptera: Aphididae) are pests of stone fruit trees in the genus Prunus globally, causing damage directly through feeding as well as transmission of plant viruses. Despite their status as cosmopolitan pests, the genus is poorly understood, with current taxonomy recognizing two, likely paraphyletic, species: Hyalopterus pruni (Koch) and Hyalopterus amygdali (Blanchard). Here we present a systematic study of Hyalopterus using a molecular phylogeny derived from mitochondrial, endosymbiont, and nuclear DNA sequences (1,320 bp) and analysis of 16 morphometric characters. The data provides strong evidence for three species within Hyalopterus, which confirms previous analyses of host plant usage patterns and suggests the need for revision of this genus. We describe a new species H. persikonus Miller, Lozier & Foottit n. sp., and present diagnostic identification keys for the genus.

Recent Problems on Bemisia tabaci Biotypes and their Transmission of Plant Viruses

Recent Problems on <I>Bemisia tabaci</I> Biotypes and their Transmission of Plant Viruses

Presença e impacto de Bemisia Tabaci (genn.) (homoptera: aleyrodidae) em culturas hortícolas em Portugal

In Portugal, Bemisia tabaci (Genn.) (Homoptera: Aleyrodidae) was first recorded in 1992, in horticultural crops. Since 1995, it has been an important pest in the Algarve, southern Portugal, where it is present the whole year round, in greenhouse crops, with high infestations during the summer. In 2006, it was installed in Alentejo and in part of Ribatejo e Oeste region. It is a serious problem to several vegetable crops, due to direct damages, but mainly by transmitting plant viruses. The most severely affected crops are greenhouse tomato and cucurbits. IPM is considered the best way to deal with the sustainable management of this problem, but the presence of viruses complicates the implementation of IPM programs. The work presented here gives an overview of the results obtained by the research activities carried out in Portugal concerning B. tabaci: geographical distribution, bioecology, biotypes identification, virus transmission, risk assessment, natural enemies’ survey and control methods. Future research work is suggested.

The P2 capsid protein of the nonenveloped rice dwarf phytoreovirus induces membrane fusion in insect host cells

Insect transmission is an essential process of infection for numerous plant and animal viruses. How an insect-transmissible plant virus enters an insect cell to initiate the infection cycle is poorly understood, especially for nonenveloped plant and animal viruses. The capsid protein P2 of rice dwarf virus (RDV), which is nonenveloped, is necessary for insect transmission. Here, we present evidence that P2 shares structural features with membrane-fusogenic proteins encoded by enveloped animal viruses. When RDV P2 was ectopically expressed and displayed on the surface of insect Spodoptera frugiperda cells, it induced membrane fusion characterized by syncytium formation at low pH. Mutational analyses identified the N-terminal and a heptad repeat as being critical for the membrane fusion-inducing activity. These results are corroborated with results from RDV-infected cells of the insect vector leafhopper. We propose that the RDV P2-induced membrane fusion plays a critical role in viral entry into insect cells. Our report that a plant viral protein can induce membrane fusion has broad significance in studying the mechanisms of virus entry into insect cells and insect transmission of nonenveloped plant and animal viruses.

Genomic resources for Myzus persicae: EST sequencing, SNP identification, and microarray design

BackgroundThe green peach aphid, Myzus persicae (Sulzer), is a world-wide insect pest capable of infesting more than 40 plant families, including many crop species. However, despite the significant damage inflicted by M. persicae in agricultural systems through direct feeding damage and by its ability to transmit plant viruses, limited genomic information is available for this species.ResultsSequencing of 16 M. persicae cDNA libraries generated 26,669 expressed sequence tags (ESTs). Aphids for library construction were raised on Arabidopsis thaliana, Nicotiana benthamiana, Brassica oleracea, B. napus, and Physalis floridana (with and without Potato leafroll virus infection). The M. persicae cDNA libraries include ones made from sexual and asexual whole aphids, guts, heads, and salivary glands. In silico comparison of cDNA libraries identified aphid genes with tissue-specific expression patterns, and gene expression that is induced by feeding on Nicotiana benthamiana. Furthermore, 2423 genes that are novel to science and potentially aphid-specific were identified. Comparison of cDNA data from three aphid lineages identified single nucleotide polymorphisms that can be used as genetic markers and, in some cases, may represent functional differences in the protein products. In particular, non-conservative amino acid substitutions in a highly expressed gut protease may be of adaptive significance for M. persicae feeding on different host plants. The Agilent eArray platform was used to design an M. persicae oligonucleotide microarray representing over 10,000 unique genes.ConclusionNew genomic resources have been developed for M. persicae, an agriculturally important insect pest. These include previously unknown sequence data, a collection of expressed genes, molecular markers, and a DNA microarray that can be used to study aphid gene expression. These resources will help elucidate the adaptations that allow M. persicae to develop compatible interactions with its host plants, complementing ongoing work illuminating plant molecular responses to phloem-feeding insects.

Plant virus transmission from the insect point of view

Although much is known about the proteins and processes within the plant cell required for efficient virus transmission, up to now, little was known about the requirements and mechanisms from the insect point of view. In this issue of PNAS, Uzest et al. (1) tackle that problem and trace the receptor for the cauliflower mosaic virus (CaMV) movement protein to a protein imbedded into the chitin matrix at the tip of the stylet of the aphid vector. In terms of epidemiology, insects are the most important factors in plant virus disease. Approximately 80% of the plant viruses depend on insect vectors for transmission (other vectors can be nematodes and fungi), and the plant virus vector interactions are very specific. Thus, the recent spreading of begomoviruses throughout America might be caused by the introduction of the old world vector Bemisia tabaci . This spreading might have provided the opportunity of preexisting viruses to be transmitted to a variety of crop plants (2). Plant viruses can be transmitted by insects in various ways. These have been classified as nonpersistent, semipersistent, and persistent, depending on the length of the … *E-mail: hohn{at}fmi.ch

A protein key to plant virus transmission at the tip of the insect vector stylet

Hundreds of species of plant viruses, many of them economically important, are transmitted by noncirculative vector transmission (acquisition by attachment of virions to vector mouthparts and inoculation by subsequent release), but virus receptors within the vector remain elusive. Here we report evidence for the existence, precise location, and chemical nature of the first receptor for a noncirculative virus, cauliflower mosaic virus, in its insect vector. Electron microscopy revealed virus-like particles in a previously undescribed anatomical zone at the extreme tip of the aphid maxillary stylets. A novel in vitro interaction assay characterized binding of cauliflower mosaic virus protein P2 (which mediates virus-vector interaction) to dissected aphid stylets. A P2-GFP fusion exclusively labeled a tiny cuticular domain located in the bottom-bed of the common food/salivary duct. No binding to stylets of a non-vector species was observed, and a point mutation abolishing P2 transmission activity correlated with impaired stylet binding. The novel receptor appears to be a nonglycosylated protein deeply embedded in the chitin matrix. Insight into such insect receptor molecules will begin to open the major black box of this scientific field and might lead to new strategies to combat viral spread.

Nepovirus transmission by longidorid nematodes

Transmission of plant viruses in nature often involves vectors which are usually plant pests. A class of soil borne invertebrates acts in this way. Ectoparasitic nematodes belonging to the Longidoridae family are responsible for the transmission of viruses from the Nepovirus genus using a semipersistant, non circulative mechanism. This passive transmission occurs during the feeding process of the nematodes on actively growing roots. However, only a few longidorid nematodes are able to acquire and subsequently transmit 12 of the 32 known Nepovirus. This singularity reflects a highly specific and strong association between the virus and the vector likely via a putative receptor on the cuticular lining of the oesophageal tract. Using a reverse genetics approach, investigations on the Grapevine fanleaf virus/Xiphinema index virus-vector association showed that the transmission specificity is solely determined by the coat protein.

Observing and recording copulation events of whiteflies on plants using a video camera

The whitefly Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) is a genetically diverse group (Frohlich et al., 1999; De Barro et al., 2000; De Barro, 2005). More than 20 biotypes have been named from populations of this species complex (Perring, 2001), and more recently the populations known have been grouped into six races plus an unsolved Asian group (De Barro et al., 2005). Some of the genetic groups of B. tabaci have been shown to differ in biological characteristics, such as host range, the ability to transmit viruses, the capacity to induce specific phytotoxic response, and feeding and mating behaviour (e.g., Bedford et al., 1994; Brown et al., 1995; Jiang et al., 1999; Perring & Symmes, 2006; Zang et al., 2006). One of the major recent events associated with the B. tabaci species complex has been the widespread invasion by the B and Q biotypes around the world in the past 20 years (Brown et al., 1995; Perring, 2001; Chu et al., 2006). These invasive biotypes have been causing enormous damage to a range of crops through phloem feeding, transmission of plant viruses, induction of phototoxic disorders, and excretion of honeydew. Circumstantial evidence has indicated that in many regions the alien B biotype has been displacing indigenous biotypes in the process of invasion (Perring, 1996; McKenzie et al., 2004; Zang et al., 2005a; 2006). It has been suggested that the mating interactions between the B and other biotypes may have played a role in the invasion of the B biotype (Perring et al., 1993; Perring, 1996; De Barro & Hart, 2000; Zang et al., 2005a; De Barro et al., 2006). However, no detailed observation on the mating behaviour of B. tabaci on plants has been made, apparently due to the lack of a feasible method for conducting large numbers of observations on behaviour on plants, although sophisticated techniques have been available for observing and recording behaviour of B. tabaci placed in a minute arena using a stereomicroscope (Li et al., 1989; Perring & Symmes, 2006). The objective of this study was to develop a cost-effective, efficient, and reliable method for observing and recording the behaviour of whitefly on live plants.

Transmission of two viruses that cause Barley Yellow Dwarf is controlled by different loci in the aphid, Schizaphis graminum.

Clonal populations of the aphid, Schizaphis graminum, have been separated into biotypes based on host preference and their ability to overcome resistance genes in wheat. Recently, several biotypes were found to differ in their ability to transmit one or more of the viruses that cause barley yellow dwarf disease in grain crops, and vector competence was linked to host preference. The genetics of host preference has been studied in S. graminum, but how this may relate to the transmission of plant viruses is unknown. Sexual morphs of a vector and nonvector S. graminum genotype were induced from parthenogenetic females and reciprocal crosses made. Eighty-nine hybrids were generated and maintained by parthenogenesis. Each hybrid was evaluated for its ability to transmit Barley yellow dwarf virus-PAV and Cereal yellow dwarf virus-RPV, and for its ability to colonize two wheat genotypes each expressing a different gene that confers resistance to S. graminum. The F1 genotypes were genetically variable for their ability to transmit virus and to colonize the aphid resistant wheat, but these traits were not genetically correlated. Individual F1 genotypes ranged in transmission efficiency from 0–100% for both viruses, although the overall mean transmission efficiency was similar to the transmission competent parent, indicating directional dominance. The direction of the cross did not significantly affect the vector competency for either virus, suggesting that maternally inherited cytoplasmic factors, or bacterial endosymbionts, did not contribute significantly to the inheritance of vector competency in S. graminum. Importantly, there was no genetic correlation between the ability to transmit Barley yellow dwarf virus and Cereal yellow dwarf virus-RPV in the F1 genotypes. These results taken together indicate that multiple loci are involved in the circulative transmission, and that the successful transmission of these closely related viruses is regulated by different sets of aphid genes.

The role of aphid salivation in the transmission of plant viruses

The role of aphid salivation in the transmission of plant viruses

Virus-Vector Interactions Mediating Nonpersistent and Semipersistent Transmission of Plant Viruses

Most plant viruses are absolutely dependent on a vector for plant-to-plant spread. Although a number of different types of organisms are vectors for different plant viruses, phloem-feeding Hemipterans are the most common and transmit the great majority of plant viruses. The complex and specific interactions between Hemipteran vectors and the viruses they transmit have been studied intensely, and two general strategies, the capsid and helper strategies, are recognized. Both strategies are found for plant viruses that are transmitted by aphids in a nonpersistent manner. Evidence suggests that these strategies are found also for viruses transmitted in a semipersistent manner. Recent applications of molecular and cell biology techniques have helped to elucidate the mechanisms underlying the vector transmission of several plant viruses. This review examines the fundamental contributions and recent developments in this area.