Aphids associated with shrubs, herbaceous plants and crops in the Maltese Archipelago (Hemiptera, Aphidoidea)

A survey of the aphids associated with Maltese shrubs, herbaceous plants and crops was carried out. Sixty six aphid species were recorded from more than 90 species of host plants. Forty eight aphids were recorded from the Maltese islands for the fi rst time bringing the total number of aphid species known from these islands to 99. New records include: Acyrthosiphon lactucae, A. pisum, Anoecia vagans, Aphis alienus, A. euphorbiae, A. hederae, A. lambersi, A. multifl orae, A. nasturtii, A. parietariae, A. picridicola, A. ruborum, A. sedi, Aulacorthum solani, Brachycaudus helichrysi, Capitophorus sp. nr. similis, Clypeoaphis suaedae, Cryptomyzus korschelti, Dysaphis apiifolia, D. foeniculus, D. pyri, D. tulipae, Hyadaphis coriandri, H. foeniculi, H. passerinii, Hyperomyzus lactucae, Idiopterus nephrelepidis, Macrosiphoniella absinthii, M. artemisiae, M. sanborni, Macrosiphum euphorbiae, Ma. rosae, Melanaphis donacis, Metopolophium dirhodum, Pterochloroides persicae, Rectinasus buxtoni, Rhopalosiphum maidis, R. padi, R. rufi abdominale, Schizaphis graminum, Semiaphis dauci, Sipha maydis, Sitobion avenae, S. fragariae, Therioaphis alatina, Uroleucon inulae, U. hypochoeridis and U. sonchi. Of these 99 aphid species, 58 are of economic importance and 16 are alien introductions. For 15 of the aphid species, a total of 22 new host-plant records are made. Ten species of ants were found attending 18 aphid species.peer-reviewe

Discovery of a Small Non-AUG-Initiated ORF in Poleroviruses and Luteoviruses That Is Required for Long-Distance Movement.

Viruses in the family Luteoviridae have positive-sense RNA genomes of around 5.2 to 6.3 kb, and they are limited to the phloem in infected plants. The Luteovirus and Polerovirus genera include all but one virus in the Luteoviridae. They share a common gene block, which encodes the coat protein (ORF3), a movement protein (ORF4), and a carboxy-terminal extension to the coat protein (ORF5). These three proteins all have been reported to participate in the phloem-specific movement of the virus in plants. All three are translated from one subgenomic RNA, sgRNA1. Here, we report the discovery of a novel short ORF, termed ORF3a, encoded near the 5' end of sgRNA1. Initially, this ORF was predicted by statistical analysis of sequence variation in large sets of aligned viral sequences. ORF3a is positioned upstream of ORF3 and its translation initiates at a non-AUG codon. Functional analysis of the ORF3a protein, P3a, was conducted with Turnip yellows virus (TuYV), a polerovirus, for which translation of ORF3a begins at an ACG codon. ORF3a was translated from a transcript corresponding to sgRNA1 in vitro, and immunodetection assays confirmed expression of P3a in infected protoplasts and in agroinoculated plants. Mutations that prevent expression of P3a, or which overexpress P3a, did not affect TuYV replication in protoplasts or inoculated Arabidopsis thaliana leaves, but prevented virus systemic infection (long-distance movement) in plants. Expression of P3a from a separate viral or plasmid vector complemented movement of a TuYV mutant lacking ORF3a. Subcellular localization studies with fluorescent protein fusions revealed that P3a is targeted to the Golgi apparatus and plasmodesmata, supporting an essential role for P3a in viral movement.ES and WAM were financed through a Gutenberg Chair (Région Alsace) grant awarded to WAM. Work in the AEF lab was funded by grants from the Wellcome Trust (088789) and the UK Biotechnology and Biological Research Council (BBSRC) (BB/J007072/1 and BB/J015652/1). WAM was also funded by a Fulbright Foundation Research Scholarship and grant number 5R01GM067104-09 from the NIH Institute of General Medical Sciences.This is the final version. It was first published by PLOS at http://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1004868#ack

Review on Barely Yellow Dwarf Viruses

Barley yellow dwarf virus (BYDV) is distributed worldwide, and infects most cereals and grasses. It is a phloem-restricted pathogen, causing yellowing, reddening, and brittleness of leaves, dwarfing, and reduction in size and number of ears and grains. BYDV is a luteovirus with small isometric particles containing an ssRNA genome, and is transmitted persistently by more than 20 aphid species. Five virus isolates have been distinguished and divided into two subgroups on the basis of cytopathology and serology. Recent serological evidence also indicates that BYDV isolates are related to other luteoviruses, suggesting that a continuous, over lapping range of viruses may be implicated in the barley yellow dwarf syndrome. Until future research clarifies this point, the term BYDV continues to be used to indicate the agent(s) involved. Perennial wild or cultivated grasses constitute a large and permanent virus pool. Primary and secondary virus spread depends on the aphid vector reproduction and flight which, in turn, are influenced by climatic conditions. Recent research on monitoring and control of aphid vectors and on development of resistant cereal cultivars has improved the prospect of minimizing losses from BYDV infections. Because of the economic importance of the BYDVs, more research is needed. The specific locations and timing of virus outbreaks, and the particular causal isolates, need to be monitored. This is will allow breeders to decide which BYDV isolate to target with transgenic resistance in a given locality. It will help growers decide whether to pay the extra premium for BYDV-resistant crops. Another area of applied research may be to engineer aphid-resistant crops. With the growing number of sequenced or partially sequenced isolates of BYDV and CYDV around the world, it’s important 1) to develop rapid means of nucleic acid-based detection (e.g., PCR), 2) to understand the epidemiology of BYDV/CYDV, and 3) to develop transgenic and other means of disease control. The better understanding of BYDV molecular mechanisms that ultimately lead to new means of controlling or mitigating the effects of the disease, and it sheds light on processes relevant to medically important viruses. In addition, further review is needed to identify all recovered BYDV and evaluation of promising treatments for use in integrated disease management strategy to manage not only BYDV but also other related viral diseases of plant. Keywords: Barley, Barley yellow dwarf virus (BYDV), and luteovirus

Purification, characterization and serological detection of virus-like particles associated with banana bunchy top disease in Australia

Isometric virus-like particles, 18 nm in diameter, have been isolated from banana (Musa spp.) affected by bunchy top disease in Australia. Banana bunchy top disease-associated virus-like particles (BBTV) banded as a single component with buoyant density of 1.28 to 1.29 g/ml in Cs2SO4 and sedimented at about 46S in isokinetic sucrose density gradients. The A 260/A 280 of purified preparations was about 1.33. A single coat protein of M r 20500 identified with antibodies to BBTV particles from Australia. Single-stranded DNA of about 1 kb as well as ssRNA smaller than 0.45 kb was also associated with the particles. A polyclonal antiserum to BBTV, suitable for use in ELISA, was prepared. Stability and antigenicity of purified BBTV was impaired by storage at pH ≥ 8.5 and freezing at -20 °C without protectants. BBTV was detected by double antibody sandwich-ELISA with monoclonal and polyclonal antibodies, in field-infected banana plants, single aphids from an infective colony, and in experimentally aphid-inoculated banana plants. After transmission of BBTV particles by aphids from a banana bunchy top disease-affected to an uninfected banana plant, the disease was induced and BBTV was detected by ELISA in symptomatic leaves only. BBTV isolates from Australia, Taiwan, People’s Republic of China, Tonga, Western Samoa and Hawaii were found to be serologically related, which suggests a common aetiology for the disease

The complete nucleotide sequence of the genome of Barley yellow dwarf virus-RMV reveals it to be a new Polerovirus distantly related to other yellow dwarf viruses

The yellow dwarf viruses (YDVs) of the Luteoviridae family represent the most widespread group of cereal viruses worldwide. They include the Barley yellow dwarf viruses (BYDVs) of genus Luteovirus, the Cereal yellow dwarf viruses (CYDVs) and Wheat yellow dwarf virus (WYDV) of genus Polerovirus. All of these viruses are obligately aphid transmitted and phloem-limited. The first described YDVs (initially all called BYDV) were classified by their most efficient vector. One of these viruses, BYDV-RMV, is transmitted most efficiently by the corn leaf aphid, Rhopalosiphum maidis. Here we report the complete 5612 nucleotide sequence of the genomic RNA of a Montana isolate of BYDV-RMV (isolate RMV MTFE87, Genbank accession no. KC921392). The sequence revealed that BYDV-RMV is a polerovirus, but it is quite distantly related to the CYDVs or WYDV, which are very closely related to each other. Nor is BYDV-RMV closely related to any other particular polerovirus. Depending on the gene that is compared, different poleroviruses (none of them a YDV) share the most sequence similarity to BYDV-RMV. Because of its distant relationship to other YDVs, and because it commonly infects maize via its vector, R. maidis, we propose that BYDV-RMV be renamed Maize yellow dwarf virus-RMV (MYDV-RMV)

Molecular interactions between Pea enation mosaic virus and its pea aphid vector

Insect transmission of plant viruses results in tremendous economic loss within the agricultural sector worldwide. Aphids account for nearly half of insect-borne plant virus transmission. Viruses in the family Luteoviridae are transmitted by aphids in a persistent-circulative manner that requires specific molecular interactions between the aphid and virus. Ingested virions cross the aphid gut and salivary gland epithelial barriers using receptors that have not been identified. We assessed the binding of a model luteovirid, Pea enation mosaic virus (PEMV), to brush border membrane vesicles (BBMV) of the pea aphid, Acyrthosiphon pisum using a two-dimensional far-western blot method. Pea aphid membrane alanyl aminopeptidase N (APN) was identified by mass spectrometry following specific binding to PEMV virions and to a PEMV coat protein-eGFP fusion peptide (CP-P-eGFP). The binding of PEMV to APN was confirmed by multiple methods including a pull-down assay, surface plasmon resonance (SPR) analysis, and by increased binding of CP-P-eGFP to baculovirus-expressed pea aphid APN in Sf9 cells. We also show that a peptide (GBP3.1) that was previously shown to impede uptake of PEMV into the pea aphid also binds to APN. Based on these results, we conclude that APN is a putative gut receptor for PEMV in the pea aphid and if confirmed would be the first insect receptor identified for a plant virus. Interestingly, PEMV appears to bind to a different, as yet unidentified, receptor in a second vector, Myzus persicae, suggesting that different gut receptors may be used by luteoviruses in different vector species. Luteoviruses are acquired when aphids ingest the phloem sap of an infected plant. Phloem proteins have been shown to associate with luteovirus particles and facilitate aphid transmission in in vitro feeding assays. We showed an increase of virus in the hemocoel of aphids fed on artificial diet containing purified PEMV with bovine serum albumin (BSA) compared to aphids fed on virus in the absence of BSA. Interestingly, BSA reduced the amount of a mutant virus lacking the minor structural protein readthrough domain (RTD) detected in the aphid hemocoel. We also demonstrated that the PEMV RTD binds to multiple aphid proteins. SPR analysis indicated that the CP and RTD both bind to BSA. Based on these data, models are presented to account for the role of the RTD and mechanism by which BSA and plant proteins facilitate virus entry into the aphid hemocoel. Little is known about the role of glycans in mediating luteovirus-aphid interactions. We used the lectins Concanavalin A (ConA) and Galanthus nivalis agglutinin (GNA) for lectin blot analysis of BBMV and confirmed that pea aphid proteins are glycosylated with mannose and glucose moieties. APN, the PEMV gut receptor, is glycosylated with mannose residues. However, we did not detect any binding of PEMV to a synthesized tri-mannose glycan that is common in insects using both isothermal titration calorimetry or a carbohydrate microarray. These results suggest that mannose by itself is not involved in PEMV-APN binding. ConA bound to PEMV indicating that viral structural proteins are glycosylated. The potential role of virus glycosylation in aphid transmission of luteoviruses is discussed. Taken together, our increased understanding of luteovirus-aphid vector interaction will facilitate research into other plant virus-insect vector systems, and the development of mitigation strategies

Review on Barely Yellow Dwarf Viruses

Barley yellow dwarf virus (BYDV) is distributed worldwide, and infects most cereals and grasses. It is a phloem-restricted pathogen, causing yellowing, reddening, and brittleness of leaves, dwarfing, and reduction in size and number of ears and grains. BYDV is a luteovirus with small isometric particles containing an ssRNA genome, and is transmitted persistently by more than 20 aphid species. Five virus isolates have been distinguished and divided into two subgroups on the basis of cytopathology and serology. Recent serological evidence also indicates that BYDV isolates are related to other luteoviruses, suggesting that a continuous, over lapping range of viruses may be implicated in the barley yellow dwarf syndrome. Until future research clarifies this point, the term BYDV continues to be used to indicate the agent(s) involved. Perennial wild or cultivated grasses constitute a large and permanent virus pool. Primary and secondary virus spread depends on the aphid vector reproduction and flight which, in turn, are influenced by climatic conditions. Recent research on monitoring and control of aphid vectors and on development of resistant cereal cultivars has improved the prospect of minimizing losses from BYDV infections. Because of the economic importance of the BYDVs, more research is needed. The specific locations and timing of virus outbreaks, and the particular causal isolates, need to be monitored. This is will allow breeders to decide which BYDV isolate to target with transgenic resistance in a given locality. It will help growers decide whether to pay the extra premium for BYDV-resistant crops. Another area of applied research may be to engineer aphid-resistant crops. With the growing number of sequenced or partially sequenced isolates of BYDV and CYDV around the world, it’s important 1) to develop rapid means of nucleic acid-based detection (e.g., PCR), 2) to understand the epidemiology of BYDV/CYDV, and 3) to develop transgenic and other means of disease control. The better understanding of BYDV molecular mechanisms that ultimately lead to new means of controlling or mitigating the effects of the disease, and it sheds light on processes relevant to medically important viruses. In addition, further review is needed to identify all recovered BYDV and evaluation of promising treatments for use in integrated disease management strategy to manage not only BYDV but also other related viral diseases of plant. Keywords: Barley, Barley yellow dwarf virus (BYDV), and luteovirus

Replication of barley yellow dwarf luteovirus-PAV RNA

Barley yellow dwarf luteovirus (BYDV)-PAV serotype, an economically important virus of small grain cereals, has a positive-sense RNA genome encoding at least six open reading frames (ORFs). The goal of the research was to determine the genes and sequences involved in the viral replication and to design efficient antiviral strategies to BYDV-PAV. Genetically engineered resistance is essential for BYDV as the natural resistance is inadequate. Antiviral constructs such as sense RNA, antisense RNA and viral polymerase gene were tested for their ability to reduce virus titre in oat protoplasts as monitored by enzyme-linked immunosorbent assay. All antiviral constructs yielded low levels of viral antigen. However, none of the above constructs showed decrease in viral RNA accumulation in Northern blot analysis. Deletion and mutation analyses were performed to determine genes and cis-acting signals involved in translation, replication and encapsidation of BYDV-PAV. ORFs 1 and 2, which encode the putative polymerase gene, were required for replication. Deletion of the coat protein (CP) gene reduced the accumulation of genomic RNA. The carboxy-terminally extended form of the CP was not necessary for replication or encapsidation. Cis-acting RNA signals in and around ORF6 were essential for viral replication. BYDV-PAV replication may be coupled to translation because defective RNAs containing various deletions were not replicated in trans by the co-inoculated wild-type helper genome. Site-directed mutagenesis was used to map the subgenomic RNA1 (sgRNA1) promoter because subgenomic promoters are putative hotspots of viral recombination and putative replication origin. Mutating the sgRNA1 transcription initiation base, G at 2670, or the nucleotides immediately flanking it, reduced sgRNA1 accumulation. Computer-predicted secondary structures in the putative sgRNA1 promoter regions of many members of subgroup I luteovirus has revealed a conserved stem-loop structure near the sgRNA1 start site. Altering the conserved ACAAA motif reduced both the genomic RNA and sgRNA1 accumulation. A premature stop codon introduced at base 2650, 90 bases from the 3\u27 end of the polymerase gene, abolished BYDV-PAV replication in oat protoplasts