[Show abstract][Hide abstract] ABSTRACT: In Venezuela, cucurbit viruses have been associated with important yield losses. Therefore, an extensive survey was conducted to determine the major cucurbit viruses in this country. Leaf samples from 284 cucurbit plants exhibiting virus-like symptoms were collected mainly in 2009–2010 from several states of Venezuela. They were assessed for viral infection by polymerase chain reaction (PCR) for Melon chlorotic mosaic virus (MeCMV) and reverse transcriptase (RT)-PCR for Papaya ringspot virus (PRSV), Zucchini yellow mosaic virus (ZYMV), Watermelon mosaic virus (WMV), Cucumber mosaic virus (CMV), Squash mosaic virus (SqMV) and Cucurbit aphid-borne yellows virus (CABYV). The most common virus in cucurbit fields, MeCMV, was present in 65·8% of samples. Its associated alphasatellite was found in 78% of samples positive for MeCMV. PRSV, ZYMV and WMV were found with different prevalence: 34·2, 32·4 and 1·1% respectively. CMV was also detected (6·7%) but SqMV and CABYV were not found. Single infections were more frequent than mixed infections (56·4 and 38·6%, respectively). For ZYMV, comparison and phylogenetic analyses of either polymerase and coat protein (NIb-CP) partial sequences or CP complete sequences revealed a low genetic diversity within Venezuelan isolates. Thirty-four ZYMV isolates were used for serological and biological analysis. Thirteen monoclonal antibodies showed a major group of isolates spread in several states and two groups located in Zulia only. Venezuelan ZYMV isolates showed biological variability on cucurbit cultivars susceptible, tolerant or resistant to ZYMV. Resistance to ZYMV in cucumber appears potentially durable, whereas resistance or tolerance in zucchini and melon may be easily overcome.
[Show abstract][Hide abstract] ABSTRACT: Zucchini yellow mosaic virus (ZYMV, genus Potyvirus) causes important crop losses in cucurbits worldwide. In France, ZYMV epidemics are sporadic but occasionally very severe. This contrasts with Watermelon mosaic virus (WMV, genus Potyvirus) which causes regular and early epidemics. Factors influencing ZYMV epidemiology are still poorly understood. In order to gain new insights on the ecology and epidemiology of this virus, a 5-year multilocation trial was conducted in which ZYMV spread and populations were studied in each of the 20 plot/year combinations and compared with WMV. Search for ZYMV alternative hosts was conducted by testing weeds growing naturally around one plot and also by checking ZYMV natural infections in selected ornamental species. Although similar ZYMV populations were observed occasionally in the same plot in two successive years suggesting the occurrence of overwintering hosts nearby, only two Lamium amplexicaule plants were found to be infected by ZYMV of 3459 weed samples that were tested. The scarcity of ZYMV reservoirs contrasts with the frequent detection of WMV in the same samples. Since ZYMV and WMV have many aphid vectors in common and are transmitted with similar efficiencies, the differences observed in ZYMV and WMV reservoir abundances could be a major explanatory factor for the differences observed in the typology of ZYMV and WMV epidemics in France. Other potential ZYMV alternative hosts have been identified in ornamental species including begonia. Although possible in a few cases, exchanges of populations between different plots located from 500m to 4km apart seem uncommon. Therefore, the potential dissemination range of ZYMV by its aphid vectors seems to be rather limited in a fragmented landscape.
[Show abstract][Hide abstract] ABSTRACT: Although the biological variability of Watermelon mosaic virus is limited, isolates from the three main molecular groups differ in their ability to infect systemically Chenopodium quinoa. Mutations were introduced in a motif of three or five amino acids located in the N-terminal part of the coat protein, and differing in isolates from group 1 (motif: lysine-glutamic acid-alanine (Lys-Glu-Ala) or KEA, systemic on C. quinoa), group 2 (Lys-Glu-Thr or KET, not systemic on C. quinoa) and group 3 (KEKET, not systemic on C. quinoa). Mutagenesis of KEKET in an isolate from group 3 to KEA or KEKEA was sufficient to make the virus systemic on C. quinoa, whereas mutagenesis to KET had no effect. Introduction of a KEA motif in Zucchini yellow mosaic virus coat protein also resulted in systemic infection on C. quinoa. These mutations had no obvious effect on the disorder profile or potential post-translational modifications of the coat protein as determined in silico.
[Show abstract][Hide abstract] ABSTRACT: In recent years, three new potyviruses have been described in the papaya ringspot virus (PRSV) cluster. In addition, two types of PRSV are recognized, type W, infecting cucurbit plants, and type P, infecting papaya and also cucurbits. A third type, PRSV-T, was also partially described in Guadeloupe. Complete genome sequencing of four PRSV-T isolates showed that this virus is a related virus that is distinct from PRSV, and the name zucchini tigré mosaic virus (ZTMV) is proposed, in reference to the typical symptoms observed in zucchini squash. Eleven other viral isolates from different geographic origins were confirmed as ZTMV isolates using the complete sequence of the cylindrical inclusion (CI) coding region, whereas pairwise sequence similarities in the coat protein (CP) coding region did not unambiguously distinguish ZTMV isolates from PRSV isolates. The use of the CI coding region for species demarcation appears more suitable than the CP coding region for closely related viruses. Principal coordinates analysis based on the biological behavior of the viral isolates studied clustered PRSV-P, PRSV-W and ZTMV isolates into three different groups. Therefore, ZTMV is different from PRSV in its molecular and biological properties.
Archives of Virology 08/2013; · 2.03 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Plant viruses are generally considered incapable of infecting vertebrates. Accordingly, they are not considered harmful for humans. However, a few studies questioned the certainty of this paradigm. Tobacco mosaic virus (TMV) RNA has been detected in human samples and TMV RNA translation has been described in animal cells. We sought to determine if TMV is detectable, persists, and remains viable in the lung tissues of mice following intratracheal inoculation, and we attempted to inoculate mouse macrophages with TMV. In the animal model, mice were intratracheally inoculated with 10(11) viral particles and were sacrificed at different time points. The virus was detected in the mouse lungs using immunohistochemistry, electron microscopy, real-time RT-PCR and sequencing, and its viability was studied with an infectivity assay on plants. In the cellular model, the culture medium of murine bone marrow derived macrophages (BMDM) was inoculated with different concentrations of TMV, and the virus was detected with real-time RT-PCR and immunofluorescence. In addition, anti-TMV antibodies were detected in mouse sera with ELISA. We showed that infectious TMV could enter and persist in mouse lungs via the intratracheal route. Over 14 days, the TMV RNA level decreased by 5 log(10) copies/ml in the mouse lungs and by 3.5 log(10) in macrophages recovered from bronchoalveolar lavage. TMV was localized to lung tissue, and its infectivity was observed on plants until 3 days after inoculation. In addition, anti-TMV antibody seroconversions were observed in the sera from mice 7 days after inoculation. In the cellular model, we observed that TMV persisted over 15 days after inoculation and it was visualized in the cytoplasm of the BMDM. This work shows that a plant virus, Tobacco mosaic virus, could persist and enter in cells in mammals, which raises questions about the potential interactions between TMV and human hosts.
PLoS ONE 01/2013; 8(1):e54993. · 3.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The availability of an infectious cDNA clone is a prerequisite for genetic studies on RNA viruses. However, despite important improvement in molecular biology techniques during the last decades, obtaining such clones often remains tedious, time-consuming and rather unpredictable. In the case of potyviruses, cDNA clones are frequently unstable due to the toxicity of some viral proteins for bacteria. The problem can be overcome by inserting introns into the viral sequence but this requires additional steps in the cloning process and depends on the availability of suitable restriction sites in the viral sequence or adjunction of such sites by mutagenesis. Homologous recombination in yeast rather than in vitro restriction and ligation can be used to build infectious clones or other viral constructs. This paper describes how, by using recombination in yeast and fusion PCR, infectious intron-containing clones were obtained within a few weeks for two strains of watermelon mosaic virus (WMV, Potyvirus), whereas previous attempts using "classical" cloning techniques had failed repeatedly. Using the same approach, intronless infectious clones of two other potyviruses, zucchini yellow mosaic virus (ZYMV) and papaya ringspot virus (PRSV), were obtained in less than two weeks.
Journal of virological methods 04/2012; 183(1):94-7. · 2.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Cucurbit crops may be affected by at least 28 different viruses in the Mediterranean basin. Some of these viruses are widely distributed and cause severe yield losses while others are restricted to limited areas or specific crops, and have only a negligible economic impact. A striking feature of cucurbit viruses in the Mediterranean basin is their always increasing diversity. Indeed, new viruses are regularly isolated and over the past 35 years one "new" cucurbit virus has been reported on average every 2 years. Among these "new" viruses some were already reported in other parts of the world, but others such as Zucchini yellow mosaic virus (ZYMV), one of the most severe cucurbit viruses and Cucurbit aphid-borne yellows virus (CABYV), one of the most prevalent cucurbit viruses, were first described in the Mediterranean area. Why this region may be a potential "hot-spot" for cucurbit virus diversity is not fully known. This could be related to the diversity of cropping practices, of cultivar types but also to the important commercial exchanges that always prevailed in this part of the world. This chapter describes the major cucurbit viruses occurring in the Mediterranean basin, discusses factors involved in their emergence and presents options for developing sustainable control strategies.
Advances in Virus Research 01/2012; 84:67-126. · 2.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Watermelon mosaic virus (WMV, genus Potyvirus, family Potyviridae) was reported for the first time in France in 1974, and it is now the most prevalent virus in cucurbit crops. In 2000, new strains referred as 'emerging' (EM) strains were detected in South-eastern France. EM strains are generally more severe and phylogenetically distinct from those previously reported in this country and referred as 'classic' (CL) strains. Since 2000, EM strains have been progressively replacing CL strains in several areas where they co-exist. In order to explain this rapid shift in virus populations, the biological properties of a set of 17 CL and EM WMV isolates were compared. No major differences were observed when comparing a limited host range including 48 different plant species or cultivars. Only two species were differential; Chenopodium quinoa was systemically infected by CL and not by EM isolates whereas Ranunculus sardous was systemically infected by EM and not by CL isolates. A considerable variability was observed in aphid transmission efficiencies but this could not be correlated to the CL or EM types. Two subsets of five isolates of each group were used to compare aphid transmission efficiencies from single and double (CL-EM) infections using six different cucurbit and non-cucurbit hosts. EM isolates were generally better transmitted from mixed CL-EM infections than CL isolates and CL transmission rates were significantly lower from double than from single infections. Cross-protection was only partial between CL and EM strains leading to frequent double infections, and only a slight asymmetry was observed in cross-protection efficiencies. Since double infections occur very commonly in fields, the preferential transmission of EM from mixed CL-EM infections could be one of the factors leading to the displacement of CL isolates by EM isolates.
Virus Research 05/2011; 159(2):115-23. · 2.75 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Since their introduction in south-eastern France around 1999, new, 'emerging' (EM) strains of watermelon mosaic virus (WMV) coexist with the 'classic' (CL) strains present for more than 40 years. This situation constitutes a unique opportunity to estimate the frequency of recombinants appearing in the few years following introduction of new strains of a plant RNA virus. Molecular analyses performed on more than 1000 isolates from epidemiological surveys (2004-2008) and from experimental plots (2009-2010), and targeting only recombinants that became predominant in at least one plant, revealed at least seven independent CL/EM or EM/EM recombination events. The frequency of recombinants involving at least one EM parent in the natural populations tested was on the order of 1 %. No new recombinant was detected for more than 1 year, and none but one in more than one location. In tests comparing host range and aphid transmissibility, the new recombinants did not display a better fitness than their 'parental' isolates. No recombinant was detected from artificial mixed infections of CL and EM isolates of various hosts after testing more than 1500 subcultures obtained after single-aphid transmission. These results constitute one of the first estimations of the frequency of recombinants in natural conditions for a plant RNA virus. This suggests that although viable recombinants of WMV are not rare, and although recombination may potentially lead to new highly damaging strains, the new recombinants observed so far had a lower fitness than the parental strains and did not emerge durably in the populations.
Journal of General Virology 04/2011; 92(Pt 8):1939-48. · 3.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: All viruses are obligatory parasites that must develop tight interactions with their hosts to complete their infectious cycle. Viruses infecting plants share many structural and functional similarities with those infecting other organisms, particularly animals and fungi. Quantitative data regarding their evolutionary mechanisms--generation of variability by mutation and recombination, changes in populations by selection and genetic drift have been obtained only recently, and appear rather similar to those measured for animal viruses.This review presents an update of our knowledge of the phylogenetic and evolutionary characteristics of plant viruses and their relation to their plant hosts, in comparison with viruses infecting other organisms.
Infection, genetics and evolution: journal of molecular epidemiology and evolutionary genetics in infectious diseases 03/2011; 11(5):812-24. · 3.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We present here the first comprehensive genetic characterization of melon landraces from the humid tropics of southern India.
The genetic diversity among 50 melon landraces collected from 3 agro-ecological regions of southern India (6 agro-ecological
sub-regions) was assessed by variation at 17 SSR loci, morphological traits of plant habit and fruit, 2 yield-associated traits,
pest and disease resistance, biochemical composition (ascorbic acid, carotenoids, titrable acidity) and mineral content (P,
K, Fe, Zn). Differences among accessions were observed in plant and fruit traits. Melon germplasm with high titrable acidity,
higher than average amounts of mineral content and resistance to Cucumber mosaic virus, Zucchini yellow mosaic virus, powdery
mildew (races 1, 2, 3, 5), Fusarium wilt (races 1, 2), Aphis gossypii and leafminer was recorded in the collection. A high level of genetic variability in melon germplasm was suggested by the
SSR analysis. Comparative analysis using SSRs of the genetic variability between Indian melons from north, south, and east
regions and reference accessions of melon from Spain, France, Japan, Korea, Iraq, Zambia showed regional differentiation between
Indian melon accessions and that Indian germplasm was weakly related to the melon accessions from other parts of the world,
suggesting that an important portion of the genetic variability found within this melon collection has not been used yet for
the development of new cultivars. Additional collections of acidulus melon germplasm should be made in southern India and adequate management of this important genetic resource is clearly a
–Fungi–Genetic variation–Insect–Landraces–Microsatellite–Resistance–Taxonomic relationships–Virus
[Show abstract][Hide abstract] ABSTRACT: Since 1999, "emerging" (EM) strains of Watermelon mosaic virus (WMV) have been detected in cucurbit crops of southeastern France, probably as a result of recent introductions. Population genetic approaches were used to study the structure of EM isolates in southeastern France and to identify factors involved in their spatial distribution. A population clustering method (SAMOVA) and a maximum-difference algorithm (Monmonier's algorithm) were combined to visualize and quantify barriers to gene flow between populations. Both methods yielded similar results and two main barriers were identified. A North/South oriented barrier may be related to physical obstacles to gene flow (Rhône River, presence of an area with few cucurbit crops). Although the barrier was very strong, some "crossing" events were detected. A second barrier, oriented Northwest to Southeast, was not correlated with obvious geographical features. The two methods used here are complementary and confirm the limited spread of WMV-EM isolates. This approach can be useful in epidemiology studies to characterize the structure of viral populations and identify barriers to gene flow.
[Show abstract][Hide abstract] ABSTRACT: Disentangling the role of epidemiological factors in plant pathogen emergences is a prerequisite to identify the most likely future invaders. An example of emergence was recently observed in France: in 10 years, "classic" (CL) strains of Watermelon mosaic virus (WMV) were displaced at a regional scale by newly introduced "emerging" (EM) strains. Here we analyse a 3 years dataset describing the co-dynamics of CL and EM strains at field scale using state-space models estimating jointly: (i) probabilities of primary and secondary infection and (ii) probabilities of over-infecting with a CL [EM] strain a plant already infected with an EM [CL] strain. Results especially indicate that it is more than 3 times less probable for a CL strain to over-infect an EM infected plant than for an EM strain to over-infect a CL infected plant. To investigate if these asymmetric interactions can explain the CL/EM shift observed at regional scale, an exploratory model describing WMV epidemiology over several years in a landscape composed of a reservoir and a cultivated compartment is introduced. In most simulations a shift is observed and both strains do coexist in the landscape, reaching an equilibrium that depends on the probabilities of over-infection.
Journal of Theoretical Biology 05/2010; 265(3):377-88. · 2.35 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A natural mild isolate of Zucchini yellow mosaic virus was found to contain a mutation in the helper component (HC-Pro) within a conserved motif, "CDNQLD", located 12 residues downstream from the "FRNK" motif involved in symptom severity. Introducing the mutation in an infectious cDNA clone of ZYMV resulted in an almost complete absence of symptoms, although viral accumulation was only partially reduced. The FRNK(X)(12)CDNQLD sequence might be part of a larger motif that is conserved in potyviruses and plays a role in symptomatology and/or silencing inhibition.
Archives of Virology 03/2010; 155(3):397-401. · 2.03 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Recently, metagenomic studies have identified viable Pepper mild mottle virus (PMMoV), a plant virus, in the stool of healthy subjects. However, its source and role as pathogen have not been determined.
21 commercialized food products containing peppers, 357 stool samples from 304 adults and 208 stool samples from 137 children were tested for PMMoV using real-time PCR, sequencing, and electron microscopy. Anti-PMMoV IgM antibody testing was concurrently performed. A case-control study tested the association of biological and clinical symptoms with the presence of PMMoV in the stool. Twelve (57%) food products were positive for PMMoV RNA sequencing. Stool samples from twenty-two (7.2%) adults and one child (0.7%) were positive for PMMoV by real-time PCR. Positive cases were significantly more likely to have been sampled in Dermatology Units (p<10(-6)), to be seropositive for anti-PMMoV IgM antibodies (p = 0.026) and to be patients who exhibited fever, abdominal pains, and pruritus (p = 0.045, 0.038 and 0.046, respectively).
Our study identified a local source of PMMoV and linked the presence of PMMoV RNA in stool with a specific immune response and clinical symptoms. Although clinical symptoms may be imputable to another cofactor, including spicy food, our data suggest the possibility of a direct or indirect pathogenic role of plant viruses in humans.
PLoS ONE 01/2010; 5(4):e10041. · 3.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Tomato chlorosis virus (ToCV) and Tomato infectious chlorosis virus (TICV) are two criniviruses that are emerging worldwide, and induce similar yellowing diseases in tomato crops. While TICV is transmitted only by Trialeurodes vaporariorum, ToCV is transmitted by three whitefly species in two genera Trialeurodes vaporariorum, T. abutilonea and Bemisia tabaci. The efficiency of transmission by T. vaporariorum from plants infected by one virus or by both was compared, and the probability of virus transmission by a single whitefly was derived from group testing experiments. The estimated transmission probabilities ranged from 0·01 to 0·13, and were not significantly different between ToCV and TICV, or between single and mixed infections. Experiments using B. tabaci as a vector and source plants infected by TICV and ToCV did not reveal any functional trans-complementation for transmission of TICV by ToCV, suggesting that if this phenomenon occurs in nature, it is at a very low frequency. Possible reasons why TICV did not establish in southern France while ToCV is now endemic are discussed.
[Show abstract][Hide abstract] ABSTRACT: Cucurbit viruses are involved in complex and changing pathosystems in France, with new virus strains or species regularly reported. Zucchini yellow mosaic virus (ZYMV) is an archetypal emerging virus that was reported in France in 1979. It has since caused sporadic but occasionally very severe economic losses and its epidemiology still remains poorly understood. Partial sequencing of the viral genome has been used to characterize ZYMV isolates that occurred over a 29-year period in experimental plots at Montfavet, France (n=227), or that were received through a national survey for cucurbit viruses conducted in France from 2004 to 2007 (n=198). A total of 34 haplotypes were differentiated belonging to five molecular groups, three including isolates already described in France and two corresponding to isolates that emerged in France within the last 5 years. Comparison of haplotypes found at one location during successive years revealed contrasting situations. When they were either the same or closely related haplotypes, this suggested the availability of overwintering hosts, whereas when they belonged to different molecular groups this indicated shifts in viral populations with possible new introductions. The contribution of molecular epidemiology in tracing the origin of ZYMV in the French West Indies is also reviewed.
Virus Research 02/2009; 141(2):190-200. · 2.75 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Severe symptoms caused by Watermelon mosaic virus (WMV) in zucchini squash leaves and fruits have been observed since 1999 in South-eastern (SE) France. Their appearance correlates with the introduction of new, "emerging" (EM) isolates distant at the molecular level from the "classic" (CL) isolates present for more than 30 years. To understand the origin and spread of EM isolates, a survey was performed between 2004 and 2007. WMV isolates collected were characterized by sequencing part of the polymerase and coat protein coding regions. This revealed the presence of EM isolates in SE France only, whereas CL isolates were widespread throughout the country. Besides, four subgroups of EM isolates were observed in SE France, suggesting multiple introductions. Recombinants between CL and EM groups, which probably arose locally, were observed during the survey. A strong geographic structure that remained stable during the 4 years was observed between different EM isolates. Our results showed that EM isolates did not spread over long distances, but rapidly replaced the pre-existing CL isolates in all sites where both groups occurred.
Virus Research 02/2009; 141(2):201-8. · 2.75 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A potyvirus was isolated from a naturally infected squash plant in Algeria in 1986. Biological and serological data have revealed that the virus, initially described as H4, is related to other cucurbit-infecting potyviruses, particularly Moroccan watermelon mosaic virus (MWMV) and Papaya ringspot virus (PRSV). To establish unequivocally the taxonomic status of H4, its full-length genome sequence was established. H4 shared identities of 70% and 65% at the amino acid level with MWMV and PRSV, respectively, indicating that H4 is a distinct species of the PRSV cluster. The name Algerian watermelon mosaic virus (AWMV) is proposed for this new potyvirus species.