Helper Component-Proteinase of Triticum Mosaic Virus Is a Viral Determinant of Wheat Curl Mite Transmission.

Triticum mosaic virus (TriMV; genus Poacevirus; family Potyviridae) is an economically important virus in the Great Plains region of the United States. TriMV is transmitted by the wheat curl mite (Aceria tosichella) Type 2 genotype but not by Type 1. Helper component-proteinase (HC-Pro) is a vector transmission determinant for several potyvirids, but the role of HC-Pro in TriMV transmission is unknown. In this study, we examined the requirement of the HC-Pro cistron of TriMV for wheat curl mite (Type 2) transmission through deletion and point mutations and constructing TriMV chimeras with heterologous HC-Pros from other potyvirids. TriMV with complete deletion of HC-Pro failed to be transmitted by wheat curl mites at detectable levels. Furthermore, TriMV chimeras with heterologous HC-Pros from aphid-transmitted turnip mosaic virus and tobacco etch virus, or wheat curl mite-transmitted wheat streak mosaic virus, failed to be transmitted by wheat curl mites. These data suggest that heterologous HC-Pros did not complement TriMV for wheat curl mite transmission. A decreasing series of progressive nested in-frame deletions at the N-terminal region of HC-Pro comprising amino acids 3 to 125, 3 to 50, 3 to 25, 3 to 15, 3 to 8, and 3 and 4 abolished TriMV transmission by wheat curl mites. Additionally, mutation of conserved His20, Cys49, or Cys52 to Ala in HC-Pro abolished TriMV transmissibility by wheat curl mites. These data suggest that the N-terminal region of HC-Pro is crucial for TriMV transmission by wheat curl mites. Collectively, these data demonstrate that the HC-Pro cistron of TriMV is a viral determinant for wheat curl mite transmission.

Survey of the citrus leprosis vector (Brevipalpus yothersi) and phytoseiids in spontaneous plants of an organic citrus orchard.

Citrus leprosis (CL) is one of the most important viral diseases in sweet orange orchards in Latin America. It is caused by members of at least five species of the so-called Brevipalpus-transmitted viruses (BTV), and the prevalent is Citrus leprosis virus C (CiLV-C). This virus has the broadest host range amongst all CL-associated viruses and is transmitted by Brevipalpus yothersi, a polyphagous mite that can colonize a large variety of host plants, including some spontaneous ground cover plants. But if, on one hand, spontaneous plants can host CL virus and vector, on the other hand, they can offer alternative food for predators, equally common in organic citrus orchards. Brevipalpus yothersi and predator mites were surveyed in 33 spontaneous plants of a Westin sweet orange orchard conducted under organic production system in Brazil, from June 2010 to April 2011. Predatory mites were identified as phytoseiids, and Iphiseiodes zuluagai was the prevalent species, representing 58% of all predators. Other phytoseiids were considered accidental species in the area. Ageratum conyzoides and Alternanthera tenella were the most represented plant host species to predators, comprising 28 and 10% of the total surveyed plants, respectively. Brevipalpus yothersi specimens were detected on various spontaneous species: A. conyzoides, A. tenella, Amaranthus deflexus, Bidens pilosa, Ipomoea quamoclit, I. cairica, Merremia cissoides, Solanum americanum, Panicum maximum, and, predominantly, Commelina benghalensis. The latter has been previously reported as host of CiLV-C as well and, therefore, it is recommended to eliminate this species from citrus orchards.

Reference genes for gene expression studies by RT-qPCR in Brevipalpus yothersi (Acari: Tenuipalpidae), the mite vector of citrus leprosis virus.

Quantitative reverse transcription PCR (RT-qPCR) is a high-throughput method to analyze the transcriptional expression of genes. Currently, no reference genes have been described for evaluating gene expression in Brevipalpus yothersi, the false spider mite, a polyphagous that act as vector of the citrus leprosis virus C (CiLV-C), an important citrus disease. This study aimed to identify the most stable reference genes in B. yothersi. The RT-qPCR expression data for selected genes were evaluated from three conditions: different developmental stages, plant hosts and acquisition of CiLV-C. To analyze the stability of the candidate reference genes we used ΔCq method, GeNorm, NormFinder, BestKeeper and RefFinder. Ubiq and GAPDH are best suited for normalizing gene expression data in viruliferous and non-viruliferous mites. Ubiq, EF1α and GAPDH are the most stable for different developmental stages. RPL13 and RPL32 are the best reference genes for approaches to B. yothersi in different host plants. Considering all the experimental conditions, Ubiq, EF1α, and GAPDH were the most stable genes. Here we developed an accurate and comprehensive RT-qPCR strategy for use in B. yothersi gene expression analysis. These results will improve the understanding of the biology of the false spider mites and their role as virus vectors.

Molecular detection of avian pathogens in poultry red mite (Dermanyssus gallinae) collected in chicken farms.

Poultry red mite (PRM, Dermanyssus gallinae) is a blood-sucking ectoparasite as well as a possible vector of several avian pathogens. In this study, to define the role of PRM in the prevalence of avian infectious agents, we used polymerase chain reaction (PCR) to check for the presence of seven pathogens: Avipox virus (APV), Fowl Adenovirus (FAdV), Marek's disease virus (MDV), Erysipelothrix rhusiopathiae (ER), Salmonella enterica (SE), Mycoplasma synoviae (MS) and Mycoplasma gallisepticum (MG). A total of 159 PRM samples collected between 2004 and 2012 from 142 chicken farms in 38 prefectures in Japan were examined. APV DNA was detected in 22 samples (13.8%), 19 of which were wild-type APV. 16S ribosomal RNA (16S rRNA) of MS was detected in 15 samples (9.4%), and the mgc2 gene of MG was detected in 2 samples (1.3%). Eight of 15 MS 16S rRNA sequences differed from the vaccine sequence, indicating they were wild-type strains, while both of the MG mgc2 gene sequences detected were identical to the vaccine sequences. Of these avian pathogen-positive mite samples, three were positive for both wild-types of APV and MS. On the other hand, the DNAs of ER, SE, FAdV and MDV were not detected in any samples. These findings indicated that PRM can harbor the wild-type pathogens and might play a role as a vector in spreading these diseases in farms.

A novel virus of the genus Cilevirus causing symptoms similar to citrus leprosis.

Citrus leprosis in Colombia was previously shown to be caused by cytoplasmic Citrus leprosis virus (CiLV-C). In 2011, enzyme-linked immunosorbent assay and reverse-transcription polymerase chain reaction (RT-PCR)-based diagnostic methods failed to identify CiLV-C from citrus samples with symptoms similar to citrus leprosis; however, virions similar to CiLV-C were observed in the cytoplasm of the symptomatic leaves by transmission electron microscopy. Furthermore, the causal organism was transmitted by the false spider mite, Brevipalpus phoenicis, to healthy citrus seedlings. A library of small RNAs was constructed from symptomatic leaves and used as the template for Illumina high-throughput parallel sequencing. The complete genome sequence and structure of a new bipartite RNA virus was determined. RNA1 (8,717 nucleotides [nt]) contained two open reading frames (ORFs). ORF1 encoded the replication module, consisting of five domains: namely, methyltransferase (MTR), cysteine protease-like, FtsJ-MTR, helicase (Hel), and RNA-dependent RNA polymerase (RdRp); whereas ORF2 encoded the putative coat protein. RNA2 (4,989 nt) contained five ORFs that encode the movement protein (MP) and four hypothetical proteins (p7, p15, p24, and p61). The structure of this virus genome resembled that of CiLV-C except that it contained a long 3' untranslated terminal region and an extra ORF (p7) in RNA2. Both the RNA1 and RNA2 of the new virus had only 58 and 50% nucleotide identities, respectively, with known CiLV-C sequences and, thus, it appears to be a novel virus infecting citrus. Phylogenetic analyses of the MTR, Hel, RdRp, and MP domains also indicated that the new virus was closely related to CiLV-C. We suggest that the virus be called Citrus leprosis virus cytoplasmic type 2 (CiLV-C2) and it should be unambiguously classified as a definitive member of the genus Cilevirus. A pair of CiLV-C2 genome-specific RT-PCR primers was designed and validated to detect its presence in citrus leprosis samples collected from the Casanare and Meta states in Colombia.

Population genetics of the wheat curl mite (Aceria tosichella Keifer) in Australia: implications for the management of wheat pathogens.

The wheat curl mite (WCM), Aceria tosichella Keifer, is a polyphagous eriophyoid mite and the primary vector of wheat streak mosaic virus (WSMV) and five other viral pathogens in cereals. Previous research using molecular markers and a series of laboratory experiments found A. tosichella in Australia to consist of two genetically distinct lineages, which have broad overlapping distributions and differ in their ability to transmit WSMV under controlled conditions. This pattern of transmission also appears to be apparent in the field, whereby a strong association between WSMV detection and a single WCM lineage has been detected. In this study, we conduct a population genetic analysis and provide information on the genetic structure of the Australian viruliferous WCM lineage. We assessed genetic differentiation of 16 WCM populations using nine microsatellite markers. Strong evidence for extensive gene flow and low genetic structuring throughout the Australian wheatbelt was evident, with an exception for Western Australian and far north Queensland populations that appear to be genetically isolated. The data also indicate genetic patterns consistent with an arrhenotokous parthenogenetic mode of reproduction. Implications of these findings are discussed with reference to the management of WCM and associated cereal pathogens in Australia and overseas.

The complete genome sequence of Triticum mosaic virus, a new wheat-infecting virus of the High Plains.

The genome of Triticum mosaic virus (TriMV), a recently discovered mite-transmitted wheat potyvirus, was sequenced, characterized, and compared to other members of the family Potyviridae. TriMV has a single mRNA strand of 10,266 nucleotides with a predicted polyprotein consisting of 3,112 peptides. Protein alignments of the coat protein demonstrate that TriMV has 45.9% identity to Sugarcane streak mosaic virus strain AP (SCSMV-AP), but shares only 23.2% identity to Wheat streak mosaic virus. Although TriMV is mite-transmitted and could be placed in the genus Tritimovirus, it is significantly divergent and should be placed in the newly proposed genus Susmovirus.

Structure of the mite-transmitted Blackcurrant reversion nepovirus using electron cryo-microscopy.

Blackcurrant reversion nepovirus (BRV; genus Nepovirus) has a single-stranded, bipartite RNA genome surrounded by 60 copies of a single capsid protein (CP). BRV is the most important mite-transmitted viral pathogen of the Ribes species. It is the causal agent of blackcurrant reversion disease. We determined the structure of BRV to 1.7 nm resolution using electron cryo- microscopy (cryoEM) and image reconstruction. The reconstruction reveals a pseudo T=3 viral capsid similar to that of tobacco ringspot virus (TRSV). We modelled the BRV capsid protein to that of TRSV and fitted it into the cryoEM reconstruction. The fit indicated that the extended C-terminus of BRV-CP is located on the capsid surface and the N-terminus on the interior. We generated peptide antibodies to two putatively exposed C-terminal sequences and these reacted with the virus. Hence homology modelling may be useful for defining epitopes for antibody generation for diagnostic testing of BRV in commercial crops.

Substitution of conserved cysteine residues in wheat streak mosaic virus HC-Pro abolishes virus transmission by the wheat curl mite.

Substitutions in the amino-proximal region of wheat streak mosaic virus (WSMV) HC-Pro were evaluated for effects on transmission by the wheat curl mite (Aceria tosichella Keifer). Alanine substitution at cysteine residues 16, 46 and 49 abolished vector transmission. Although alanine substitution at Cys(20) had no effect, substitution with arginine reduced vector transmission efficiency. Random substitutions at other positions (Lys(7) to Asn, Asn(19) to Ile, and Arg(45) to Lys) did not affect vector transmission. These results suggest that a zinc-finger-like motif (His(13)-X2-Cys(16)-X29-Cys(46)-X2-Cys(49)) in WSMV HC-Pro is essential for vector transmission.

Inclusion body disease in snakes: a review and description of three cases in boa constrictors in Belgium.

Inclusion body disease, a fatal disorder in Boidae, is reviewed, and three cases in boa constrictors, the first reported cases in Belgium, are described. The snakes showed nervous signs, and numerous eosinophilic intracytoplasmic inclusions, which are considered to be characteristic of the disease, were found in the liver and pancreas. The disease is suspected to be caused by a retrovirus, but transmission electron microscopic examinations of several tissues from one of the snakes did not reveal particles with a typical retroviral morphology.

Nested deletion analysis of Wheat streak mosaic virus HC-Pro: Mapping of domains affecting polyprotein processing and eriophyid mite transmission.

A series of in-frame and nested deletion mutations which progressively removed 5'-proximal sequences of the Wheat streak mosaic virus (WSMV) HC-Pro coding region (1152 nucleotides) was constructed and evaluated for pathogenicity to wheat. WSMV HC-Pro mutants with 5'-proximal deletions of 12 to 720 nucleotides systemically infected wheat. Boundary sequences flanking the deletions were stable and unaltered by passage through plants for all deletion mutants except HCD12 (lacking HC-Pro codons 3-6) that exhibited strong bias for G to A substitution at nucleotide 1190 in HC-Pro codon 2 (aspartic acid to asparagine). HC-Pro mutants with 5'-proximal deletions of up to 720 nucleotides retained autoproteolytic activity in vitro. In contrast, 5'-proximal deletion of 852 nucleotides of the HC-Pro coding region (HCD852) abolished both infectivity and in vitro proteolytic activity, confirming that the proteolytic domain of WSMV HC-Pro resides within the carboxy-terminal third of the protein and includes the cysteine proteinase motif (GYCY) conserved among four genera of the family Potyviridae. Inoculation of wheat with HC-Pro deletion mutants also bearing the GUS reporter gene revealed that HCD852 was unable to establish primary infection foci in inoculated leaves, indicating that processing of the P3 amino-terminus was essential. Deletion of as few as 24 nucleotides of HC-Pro (codons 3-10) eliminated transmission by the eriophyid mite vector Aceria tosichella Keifer. Collectively, these results demonstrated similar organization of proteinase and vector transmission functional domains among divergent HC-Pro homologues encoded by potyviruses and tritimoviruses.

Plant virus HC-Pro is a determinant of eriophyid mite transmission.

The eriophyid mite transmitted Wheat streak mosaic virus (WSMV; genus Tritimovirus, family Potyviridae) shares a common genome organization with aphid transmitted species of the genus Potyvirus. Although both tritimoviruses and potyviruses encode helper component-proteinase (HC-Pro) homologues (required for nonpersistent aphid transmission of potyviruses), sequence conservation is low (amino acid identity, approximately 16%), and a role for HC-Pro in semipersistent transmission of WSMV by the wheat curl mite (Aceria tosichella [Keifer]) has not been investigated. Wheat curl mite transmissibility was abolished by replacement of WSMV HC-Pro with homologues of an aphid transmitted potyvirus (Turnip mosaic virus), a rymovirus (Agropyron mosaic virus) vectored by a different eriophyid mite, or a closely related tritimovirus (Oat necrotic mottle virus; ONMV) with no known vector. In contrast, both WSMV-Sidney 81 and a chimeric WSMV genome bearing HC-Pro of a divergent strain (WSMV-El Batán 3; 86% amino acid sequence identity) were efficiently transmitted by A. tosichella. Replacing portions of WSMV-Sidney 81 HC-Pro with the corresponding regions from ONMV showed that determinants of wheat curl mite transmission map to the 5'-proximal half of HC-Pro. WSMV genomes bearing HC-Pro of heterologous species retained the ability to form virions, indicating that loss of vector transmissibility was not a result of failure to encapsidate. Although titer in systemically infected leaves was reduced for all chimeric genomes relative to WSMV-Sidney 81, titer was not correlated with loss of vector transmissibility. Collectively, these results demonstrate for the first time that HC-Pro is required for virus transmission by a vector other than aphids.

Complete sequence of a picorna-like virus of the genus Iflavirus replicating in the mite Varroa destructor.

Aggregations of 27 nm virus-like particles were observed in electron microscopy images of sectioned Varroa destructor mite tissue. The scattered occurrence of individual particles and accumulation of the virions in lattices in the cytoplasm gave an apparent indication that the virus replicates in the mite. Sequence analysis of the RNA of the purified virus revealed a genome organization with high similarity to that of members of the genus Iflavirus. Phylogenetic analysis of the polymerase showed that the virus was related most closely to Deformed wing virus (DWV) and Kakugo virus (KV) of bees. The virus has a genome of 10 112 nt without the poly(A) tail, with an overall RNA genome identity of 84 % to those of DWV and KV and has one large ORF, translated into a 2893 aa polyprotein with an amino acid identity of 95 % to those of DWV and KV. The first 1455 nt of the ORF encoding the lower molecular mass structural proteins shows the greatest diversion from those of DWV and KV, with an RNA identity of 79 %, and translates to a polypeptide of 485 aa with an identity of 90 %. The name proposed for this virus is Varroa destructor virus 1 (VDV-1). To determine whether VDV-1 replicates in mites, a selective RT-PCR was done to detect the presence of the negative-sense RNA strand. The virus isolate and the closely related DWV could be discriminated by two primer sets, each specific to one virus. Both viruses replicated in the population of the mite species studied.

Brevipalpus-transmitted plant virus and virus-like diseases: cytopathology and some recent cases.

An increasing number of diseases transmitted by Brevipalpus mite species (Acari: Tenuipalpidae) is being identified that affect economically important plants such as citrus, coffee, passion fruit, orchids, and several ornamentals. All of these diseases are characterized by localized lesions (chlorotic, green spots, or ringspots) on leaves, stems, and fruits. Virus or virus-like agents are considered to be the causal agents, possibly transmitted in a circulative-propagative manner by Brevipalpus mites. The virus or virus-like particles are short, rod-like, or bacilliform, that induce two characteristic types of cell alteration: (1) 'Nuclear type'--nuclei of parenchyma and epidermal cells in the lesions often contain a large electron lucent inclusion. Short, naked, rod-like (40-50 nm x 100-110 nm) particles may be seen in the viroplasm or nucleoplasm and in the cytoplasm. These particles are commonly arranged perpendicularly on the membranes of the nuclear envelope or endoplasmic reticulum (ER). In a very few instances, they were found to be membrane-bound, within the ER cavities. (2) 'Cytoplasmic type'--short bacilliform particles (60-70 nm x 110-120 nm) are present within the cisternae of the ER and often have electron dense viroplasm of varied shapes present in the cytoplasm. Bacilliform particles may be seen budding into the ER lumen near the viroplasm. These particles resemble those of members of the Rhabdoviridae, but are shorter. The only sequenced virus of this group, orchid fleck virus (OFV), has a negative sense (bipartite) type ssRNA genome, but its organization is similar to known rhabdoviruses, which are monopartite. Both types of cytopathological effects have been found associated with citrus leprosis. In orchids, OFV has a 'nuclear type' of cytopathology, but in some species the 'cytoplasmic type' has been found associated with ringspot symptoms. In Hibiscus and Clerodendron, green spot symptoms have been associated with the cytoplasmic type of cell alteration, while chlorotic spots, in the same species, are associated with the nuclear type. In a few cases, both types of cytopathological effects have been found in the same tissue and cell.

Multiple interactions among proteins encoded by the mite-transmitted wheat streak mosaic tritimovirus.

The genome organization of the mite-transmitted wheat streak mosaic virus (WSMV) appears to parallel that of members of the Potyviridae with monopartite genomes, but there are substantial amino acid dissimilarities with other potyviral polyproteins. To initiate studies on the functions of WSMV-encoded proteins, a protein interaction map was generated using a yeast two-hybrid system. Because the pathway of proteolytic maturation of the WSMV polyprotein has not been experimentally determined, random libraries of WSMV cDNA were made both in DNA-binding domain and activation domain plasmid vectors and introduced into yeast. Sequence analysis of multiple interacting pairs revealed that interactions largely occurred between domains within two groups of proteins. The first involved interactions among nuclear inclusion protein a, nuclear inclusion protein b, and coat protein (CP), and the second involved helper component-proteinase (HC-Pro) and cylindrical inclusion protein (CI). Further immunoblot and deletion mapping analyses of the interactions suggest that subdomains of CI, HC-Pro, and P1 interact with one another. The two-hybrid assay was then performed using full-length genes of CI, HC-Pro, P1, P3, and CP, but no heterologous interactions were detected. In vitro binding assay using glutathione-S-transferase fusion proteins and in vitro translation products, however, revealed mutual interactions among CI, HC-Pro, P1, and P3. The failure to detect interactions between full-length proteins by the two-hybrid assay might be due to adverse effects of expression of viral proteins in yeast cells. The capacity to participate in multiple homomeric and heteromeric molecular interactions is consistent with the pleiotropic nature of many potyviral gene mutants and suggests mechanisms for regulation of various viral processes via a network of viral protein complexes.

Black currant reversion disease--the probable causal agent, eriophyid mite vectors, epidemiology and prospects for control.

Black currant reversion disease and the vector of its causal agent, the black currant gall mite Cecidophyopsis ribis, have been recognised for at least 100 years and are the two most damaging organisms of black currant crops world-wide. However, the molecular characterisation of these two organisms has begun to be determined in only the last few years. The probable causal agent of reversion disease, Black currant reversion associated virus (BRAV), belongs to the genus Nepovirus, has isometric particles c. 28 nm in diameter that contain a single major polypeptide of c. 55 KDa and two polyadenylated ssRNA species of 7700 nt and 6400 nt. Some particle preparations also contain a satellite ssRNA species of 1432 nt. Using immuno-capture RT-PCR and primers based on the genomic RNA of BRAV, this virus was shown to be closely associated with reversion disease. Analysis of Cecidophyopsis mite rDNA, identified rapidly and unambiguously the three known species on Ribes and distinguished four new ones. Resistance to the reversion agent and to the gall mite vector has been introduced into black currant and has given effective control of these respective organisms in the field. These findings and their significance for the ecology, epidemiology and control of variants of these two organisms are reviewed and discussed.

Sensibilizaçäo atópica em escolares e adultos de Curitiba, Paraná / Atopic sensitization among schoolchildren and adults in Curitiba, Paraná

Objetivo: Determinar a freqüência de sensibilizaçäo atópica à Dermatophagoides pteronyssinus (DP) e Lolium multiflorum ( Lolium ) em escolares e adultos residentes em Curitiba, Paraná. Casuística e método: Foram avaliados 3271 escolares (13 e 14 anos), provenientes de 43 escolas de Curitiba e 3041 adultos (idade > 20anos) funcionários, médicos do Hospital de Clínicas e adultos da UFPR. Realizou-se teste cutâneo alérgico por puntura (TCA) com dois extratos alergênicos: DP 5000 AU/mL e Lolium 1:30 peso/volume (Bayer Corporation, USA). A leitura foi feita após 15 minutos e considerada reaçäo positiva aquela com pápula igual ou superior a 3 mm de diâmetro. Resultados: Observou-se uma freqüência de TCA positivo para DP em 31,3 por cento das crianças e 38,9 por cento dos adultos e para Lolium 4,7 por cento das crianças e 15,4 por cento dos adultos. A sensibilizaçäo exclusiva ao DP em crianças foi de 28,1 por cento, ao Lolium 1,5 por cento e a ambos 3,2 por cento. Em adultos, os valores foram de 26,8 por cento de sensibilidade exclusiva ao DP e 3,3 por cento ao Lolium e para ambos de 12,1 por cento. Conclusäo: Os resultados revelam a alta freqüência de sensibilizaçäo aos ácaros da poeira domiciliar na populaçäo geral e maior freqüência de reaçäo ao pólen de gramíneas em adulto do que em crianças.

Characterization of the coat protein gene of mite-transmitted blackcurrant reversion associated nepovirus.

The nucleotide sequence of the 3' terminal 3105 nucleotides (nt) of RNA2 of blackcurrant reversion associated virus (BRAV), the first mite-transmitted member of the nepovirus group, has been determined. The sequence contains an open reading frame of 1744 nt in the virus-sense strand, a 3' untranslated region of 1360 nt and a 3' poly(A) tail. Analysis of the amino-terminal residues of purified coat protein (CP) suggests that the CP gene is located between nts 1361 and 2959 (from the 3' terminus) in the RNA2, and that Asp/Ser is the proteolytic cleavage site of CP in the RNA2 encoded polyprotein. The predicted translation product from the CP gene is a polypeptide of 533 amino acids with a calculated Mr of 57 561. The amino acid sequence of BRAV CP showed highest similarity to blueberry leaf mottle virus (BLMV), and tomato ringspot virus (ToRSV), two members of the proposed sub-group three of nepoviruses possessing large RNA2 components. Nucleic and amino acid sequence comparisons between BRAV CP and the CPs of other nepoviruses indicate that specific conserved nepovirus CP domains occur in the BRAV CP thus confirming that BRAV is a member of the subgroup three of nepoviruses. reserved.

The complete nucleotide sequence and genome organization of the mite-transmitted brome streak mosaic rymovirus in comparison with those of potyviruses.

A virus isolate, designated as 11-Cal, originating from southern France has been identified as an isolate of the mite-transmitted brome streak mosaic rymovirus (BrSMV) by serological and morphological properties. BrSMV is a member of the genus Rymovirus of the family Potyviridae. The complete nucleotide sequence of the RNA genome of BrSMV has been determined. The assembled RNA is 9672 nucleotides in length, excluding a 3'-terminal poly(A)sequence. The RNA contains one open reading frame (ORF) of 9282 nucleotides coding for a polyprotein of 3093 amino acids. A comparison with typical potyvirus showed that BrSMV has a similar genome organization. The predicted cleavage sites of the polyprotein of BrSMV are similar to those of potyviruses. Nevertheless, unusual dipeptides are proposed in two cases. Based on the proposed location of the cleavage sites nine mature proteins are predicted. Specific motifs, described for potyviral polyproteins, are almost all present in the polyprotein of BrSMV, too. However, only an incomplete zinc-finger motif is present in the potential helper component and the motif for aphid transmission in the coat protein is not found. Several alignments of amino acid sequences showed less similarity between BrSMV and potyviruses than between different potyviruses.