Cucumber Mosaic Virus Infection Research Articles

Domains of the cucumber mosaic virus 2b silencing suppressor protein affecting inhibition of salicylic acid-induced resistance and priming of salicylic acid accumulation during infection

The cucumber mosaic virus (CMV) 2b silencing suppressor protein allows the virus to overcome resistance to replication and local movement in inoculated leaves of plants treated with salicylic acid (SA), a resistance-inducing plant hormone. In Arabidopsis thaliana plants systemically infected with CMV, the 2b protein also primes the induction of SA biosynthesis during this compatible interaction. We found that CMV infection of susceptible tobacco (Nicotiana tabacum) also induced SA accumulation. Utilization of mutant 2b proteins expressed during infection of tobacco showed that the N- and C-terminal domains, which had previously been implicated in regulation of symptom induction, were both required for subversion of SA-induced resistance, while all mutants tested except those affecting the putative phosphorylation domain had lost the ability to prime SA accumulation and expression of the SA-induced marker gene PR-1.

Biochemical and physiological mechanisms underlying effects of Cucumber mosaic virus on host‐plant traits that mediate transmission by aphid vectors

The transmission of insect-vectored diseases entails complex interactions among pathogens, hosts and vectors. Chemistry plays a key role in these interactions; yet, little work has addressed the chemical ecology of insect-vectored diseases, especially in plant pathosystems. Recently, we documented effects of Cucumber mosaic virus (CMV) on the phenotype of its host (Cucurbita pepo) that influence plant-aphid interactions and appear conducive to the non-persistent transmission of this virus. CMV reduces host-plant quality for aphids, causing rapid vector dispersal. Nevertheless, aphids are attracted to the elevated volatile emissions of CMV-infected plants. Here, we show that CMV infection (1) disrupts levels of carbohydrates and amino acids in leaf tissue (where aphids initially probe plants and acquire virions) and in the phloem (where long-term feeding occurs) in ways that reduce plant quality for aphids; (2) causes constitutive up-regulation of salicylic acid; (3) alters herbivore-induced jasmonic acid biosynthesis as well as the sensitivity of downstream defences to jasmonic acid; and (4) elevates ethylene emissions and free fatty acid precursors of volatiles. These findings are consistent with previously documented patterns of aphid performance and behaviour and provide a foundation for further exploration of the genetic mechanisms responsible for these effects and the evolutionary processes that shape them.

The First Report of Cucumber Mosaic Virus Infecting Water Chestnut in China.

Water chestnut (Eleocharis dulcis), which is cultivated worldwide today, first originated in India and China. It is a popular seasonal aquatic vegetable valuable to people for its sweet crisp taste and rich nutrition. In October 2012, field-grown water chestnut seedlings (E. dulcis) showing mosaic, chlorotic, dwarfing, and malformed symptoms were observed in Fanggaoping Town, Tuanfeng County, Hubei Province, China. Sap from leaf-like stems of two symptomatic seedlings (BQ6 and BQ7) were mechanically inoculated onto Nicotiana glutinosa plants using 0.01 M phosphate buffer (pH 7.4) to investigate whether viral etiology was responsible for the disease. Typical symptoms of chlorosis and systemic mosaic similar to that inflicted by Cucumber mosaic virus (CMV) were observed on inoculated N. glutinosa leaves 13 days post inoculation, whereas mock inoculated seedlings remained symptomless. Three naturally field-grown symptomatic water chestnut and the inoculated N. glutinosa seedlings, together with a healthy water chestnut plant as negative control, were sampled. Double-antibody sandwich (DAS)-ELISA with antisera against CMV using commercial kits (Agdia, Elkhart, IN) was carried out to detect and confirm the presence of CMV. The symptomic water chestnut and inoculated N. glutinosa seedlings tested positive for CMV. Total RNAs were extracted using the SDS column isolation method from leaves of the inoculated N. glutinosa and stems of 13 field-grown symptomatic water chestnuts. The extracted RNAs were subjected to reverse transcription. The first-round PCR was carried out using the obtained cDNAs as template with the CMV specific primer set CMV-3F (5'-GCGATGYCGTGTTGAGAAG-3') and CMV-3R (5'-TTTAGCCGTAAGCTGGATGGA-3') targeting a 983-bp fragment covering 657 nt of the whole CP and partial flanking sequence within RNA3 referred as 'Fny' strain in GenBank (Accession No. D10538). The resulting amplicons were diluted 1:20 and further amplified with the nested-primer set CMV-P1 (5'-ATGGACAAATCTGAATCAACC-3') and CMV-P2 (5'-TAAGCTGGATGGACAACCCGT-3') targeting a fragment of 777 bp corresponding to the complete CP followed by part of 3'-UTRs of RNA3 (1). The amplicons of the expected size of ~777-bp were consistently amplified from 13 naturally infected water chestnuts and inoculated N. glutinosa. The PCR product derived from BQ6 isolate was cloned and three clones sequenced in both directions. The sequence (GenBank Accession No. KF268463) was analyzed by MEGA5 software (3). Sequence comparison of the complete CP gene of BQ6 isolate showed 98% nt and 99% amino acid (aa) identity with CMV isolate RP6 from South Korea (GenBank Accession No. KC527735) in subgroup I and had low similarities of 76% nt and 80% aa to that of CMV isolate infecting Trifolium from Hungary (GenBank Accession No. L15336) belonging to subgroup II of CMV. Phylogenetic analysis showed BQ6 isolate was more closely related to the isolates belonging to IB subgroup of CMV (GenBank Accession Nos. EF153739, DQ302715, and KC576805) (2). To our knowledge, this is the first report of CMV infecting water chestnut (E. dulcis) in China. CMV infection may pose a significant threat to water chestnut production. This result provide information to the producer that the CMV-free seedlings should be chosen for cultivation of water chestnut.

APUM5, encoding a Pumilio RNA binding protein, negatively regulates abiotic stress responsive gene expression

BackgroundA mutant screening was carried out previously to look for new genes related to the Cucumber mosaic virus infection response in Arabidopsis. A Pumilio RNA binding protein-coding gene, Arabidopsis Pumilio RNA binding protein 5 (APUM5), was obtained from this screening.ResultsAPUM5 transcriptional profiling was carried out using a bioinformatics tool. We found that APUM5 was associated with both biotic and abiotic stress responses. However, bacterial and fungal pathogen infection susceptibility was not changed in APUM5 transgenic plants compared to that in wild type plants although APUM5 expression was induced upon pathogen infection. In contrast, APUM5 was involved in the abiotic stress response. 35S-APUM5 transgenic plants showed hypersensitive phenotypes under salt and drought stresses during germination, primary root elongation at the seedling stage, and at the vegetative stage in soil. We also showed that some abiotic stress-responsive genes were negatively regulated in 35S-APUM5 transgenic plants. The APUM5-Pumilio homology domain (PHD) protein bound to the 3′ untranslated region (UTR) of the abiotic stress-responsive genes which contained putative Pumilio RNA binding motifs at the 3′ UTR.ConclusionsThese results suggest that APUM5 may be a new post-transcriptional regulator of the abiotic stress response by direct binding of target genes 3′ UTRs.

Production of cocktail of polyclonal antibodies using bacterial expressed recombinant protein for multiple virus detection

Cocktail of polyclonal antibodies (PAb) were produced that will help in multiple virus detection and overcome the limitation of individual virus purification, protein expression and purification as well as immunization in multiple rabbits. A dual fusion construct was developed using conserved coat protein (CP) sequences of Cucumber mosaic virus (CMV) and Papaya ringspot virus (PRSV) in an expression vector, pET-28a(+). The fusion protein (∼40kDa) was expressed in Escherichia coli and purified. Likewise, a triple fusion construct was developed by fusing conserved CP sequences of CMV and PRSV with conserved nucleocapsid protein (N) sequence of Groundnut bud necrosis virus (GBNV) and expressed as a fusion protein (∼50kDa) in pET-28a(+). PAb made separately to each of these three viruses recognized the double and triple fusion proteins in Western blot indicating retention of desired epitopes for binding with target antibodies. The fusion proteins (∼40kDa and ∼50kDa) were used to produce cocktail of PAb by immunizing rabbits, which simultaneously detected natural infection of CMV and PRSV or CMV, PRSV and GBNV in Cucurbitaceous, Solanaceous and other hosts in DAC-ELISA. This is the first report on production of a cocktail of PAb to recombinant fusion protein of two or three distinct viruses.

Alarming increase in the incidence of Cucumber mosaic virus in cowpea (Vigna unguiculata (L.) Walp.) in northern Nigeria

Cowpea plays a key nutritional role in the diet of the Nigerian people. Viral diseases are a major limitation to cowpea production worldwide, and thus, constant viral surveillance is crucial for monitoring and management purposes. In this study, cowpea leaf samples from fields in three northern Nigeria states, Kano, Kaduna and Niger, were tested to determine the status of six common viruses previously reported in these cowpea-producing states following the release of virus-resistant varieties. Cowpea aphid-borne mosaic virus (CABMV), Blackeye cowpea mosaic virus (BICMV), Cowpea mottle virus, Southern bean mosaic virus and Cucumber mosaic virus (CMV) were detected. Cowpea yellow mosaic virus, which was previously reported in all three states, was not detected in any of the samples tested, while CMV that was previously regarded as unimportant to cowpea production in Nigeria had the highest incidence in all three states, and the overall highest incidence of 58.8%, while CABMV had the lowest incidence (7.5%). CMV was also present in seven of the ten mixed infection combinations detected. Dual infection of CMV and BICMV, which often results in cowpea stunt, the most devastating cowpea disease in the USA, was the most frequently detected mixed infection (28.1%) and was detected in all three states. This observed elevation in CMV infection in cowpea must be closely monitored and swiftly managed to avert possible devastating crop yield losses.

Serological diagnosis and host range studies of important viral diseases of a few cucurbitaceous crops in Maharashtra, India

Around 39 well characterised viruses affect cucurbits crops in developing countries and their viral diversity may be the consequence for genetic and ecological diversity of their hosts. Indeed, cucurbits are grown in variety of climatic, environmental and agricultural conditions, and this may provide more or less favourable conditions for the specific viruses or their hosts. The presence of various viral diseases caused by different viruses in Maharashtra was studied from the infected samples collected from cucurbits and melons during the survey conducted in 2009–2010 in different locations. The virus isolates collected from various cucurbitaceous crops were established and their host ranges were studied by sap transmission. The study revealed Cucumber Mosaic Virus (CMV), Zucchini yellow mosaic virus (ZYMV), Watermelon mosaic virus (WMV) and Cucumber green mottle mosaic virus infections predominately found in Nashik region, and Watermelon bud necrosis virus (WBNV), CMV, ZYMV, WMV and Watermelon silver mottle virus (WSMoV) infections in Aurangabad and Paithan regions. In Sangamner region, the crop was mostly affected by WBNV, ZYMV and WSMoV, and CMV was found only in Sillod region. The protocols for performing sap transmission tests in assay hosts were standardised for ZYMV, CMV and WBNV. Using direct antigen-coating enzyme-linked immunosorbent assay, of all the plant parts, young leaves were found to have high concentration of virus and suitable for virus detection in screening programmes. CMV and ZYMV was found to have high concentration of virus and suitable for virus detection in screening programmes.

Cucumber mosaic virus in globe artichoke in Turkey

A survey was conducted to identify viruses infecting globe artichoke (Cynara cardunculus L. subsp. scolymus (L.) Hayek) in the most important globe artichoke-producing areas of Turkey. A total of 120 globe artichoke samples were collected from three provinces of the Aegean region in western Turkey. Samples were tested by DAS-ELISA, RT-PCR and mechanical inoculation onto indicator plants. Cucumber mosaic virus (CMV) was detected in five of the samples tested. Tomato spotted wilt virus (TSWV) and Tobacco mosaic virus (TMV) were not detected in the remaining 115 samples. In RT-PCR, amplicons of the expected size (about 540 bp) were obtained from symptomatic plants that were CMV-positive in DAS-ELISA. The sequenced 5 PCR products covering the partial CP gene revealed 99% identities at the nucleotide level with those CMV isolates. When inoculated with sap from symptomatic artichoke leaves, selected test plants developed the symptoms that are typical of CMV infection. This is the first record of CMV infecting globe artichoke in Turkey.

First Report of Cucumber mosaic virus Infecting Peperomia tuisana in Serbia.

Peperomia tuisana C.DC. ex Pittier (family Piperaceae) is an attractive succulent grown as an ornamental. Despite its tropical origins, it can be successfully grown indoors in any climate. In March 2012, three samples of P. tuisana showing virus-like symptoms were collected from a commercial greenhouse in Zemun (District of Belgrade, Serbia) in which estimated disease incidence was 80%. Infected plants showed symptoms including necrotic ringspots and line patterns that enlarged and caused necrosis of leaves. A serious leaf drop led to growth reduction and even death of the plant. Leaves from three symptomatic P. tuisana plants were sampled and analyzed by double-antibody sandwich (DAS)-ELISA using commercial diagnostic kits (Bioreba AG, Reinach, Switzerland) against the most common viral pathogens of ornamentals: Cucumber mosaic virus (CMV), Tomato spotted wilt virus (TSWV), and Impatiens necrotic spot virus (INSV) (1,2). Commercial positive and negative controls were included in each ELISA. Serological analyses showed that all plants were positive for CMV and negative for TSWV and INSV. The ELISA-positive sample (isolate 1-12) was mechanically inoculated onto five plants each of three test species as well as of healthy young P. tuisana using 0.01 M phosphate buffer (pH 7). Chlorotic local lesions on Chenopodium quinoa and severe mosaic and leaf malformations were observed on all inoculated Nicotiana tabacum 'Samsun' and N. glutinosa. Also, the virus was successfully mechanically transmitted to P. tuisana that reacted with symptoms identical to those observed on the original host plants. All mechanically inoculated plants were positive for CMV in DAS-ELISA. For further confirmation of CMV infection, reverse transcription (RT)-PCR was performed on extracts made from symptomatic P. tuisana, N. tabacum 'Samsun,' and N. glutinosa leaf materials. Total RNAs were extracted with the RNeasy Plant Mini Kit (Qiagen, Hilden, Germany) and RT-PCR was carried out using One-Step RT-PCR Kit (Qiagen). A CMV-specific primer pair, CMVCPfwd and CMVCPrev (3), which amplifies an 871-bp fragment of the entire coat protein (CP) gene and part of 3'- and 5'-UTRs, were used for both amplification and sequencing. Total RNAs obtained from the Serbian CMV isolate (HM065510) and healthy P. tuisana were used as positive and negative controls, respectively. A product of the correct predicted size was obtained in all naturally and mechanically infected plants, as well as positive control. No amplicon was recorded in the healthy control. The amplified product derived from isolate 1-12 was purified (QIAquick PCR Purification Kit, Qiagen), directly sequenced in both directions, deposited in GenBank (KC505441), and analyzed by MEGA5 software (4). Sequence comparison of the complete CP gene (657 nt) revealed that the Serbian isolate 1-12 shared the highest nucleotide identity of 99.1% (99.5% amino acid identity) with the Japanese isolate (AB006813). To our knowledge, this is the first report on the occurrence of CMV in P. tuisana in Serbia. This is also an important discovery since P. tuisana is commonly grown together with other ornamental hosts of CMV, and thus could represent a serious threat for future expansion of CMV in the greenhouse floriculture industry in Serbia.

Natural Infection of Maize by Cucumber Mosaic Virus in China

In July 2012, symptoms of irregular mosaic stripe and mottle were observed on maize leaves in field in Beijing, China. The causal pathogen was identified to be Cucumber mosaic virus (CMV) based upon reverse transcription-PCR, enzyme-linked immunosorbent assay, Western blotting and fulfilment of Koch's postulates. The isolate was named ZMBJ-CMV. Full sequence of ZMBJ-CMV RNA3 was determined, and it had the highest identity to that of strain K-CMV (95.03%) and SD-CMV (94.96%). Phylogenetic analysis revealed ZMBJ-CMV clustered with K-CMV and SD-CMV in subgroup IB. To our knowledge, this is the first report on the natural infection and phylogenetic analysis of CMV on maize in China.

Alteration of tomato microRNAs expression during fruit development upon Cucumber mosaic virus and Tomato aspermy virus infection

The economic importance of Solanaceae plant species is well documented, and tomato has become a model for fleshy fruit development and ripening studies. Plant microRNAs (miRNAs) are small endogenous RNAs that are involved in a variety of activities including plant development, signal transduction and protein degradation, as well as response to environment stress and pathogen invasion. Here in this study, we aimed at quantifying the expression alterations of nine miRNAs and target mRNAs in tomato flower and fruit development upon Cucumber mosaic virus (CMV) and Tomato aspermy virus infections. Three different CMV strains CMV-Fny, CMV-FnyΔ2b and CMV-Fny-satT1 were used in our investigation, and the miRNA/mRNA expression alterations were analyzed by real-time quantitative RT-PCR. The results shown the levels of several miRNA/mRNA pairs were increased upon virus infections. However, the increased level of individual miRNA differed for different virus strains, reflecting differences in severity of symptom phenotypes. The altered expression patterns of these miRNA/mRNA pairs and their predicted functions indicate the possible roles in flower and fruit development, and provide experimental data for understanding the miRNA-mediated phenotype alterations in tomato fruit.

ArabidopsisPumilio protein APUM5 suppressesCucumber mosaic virusinfection via direct binding of viral RNAs

Posttranscriptional/translational regulation of gene expression is mediated by diverse RNA binding proteins and plays an important role in development and defense processes. Among the RNA-binding proteins, the mammalian Pumilio RNA-binding family (Puf) acts as posttranscriptional and translational repressors. An Arabidopsis Puf mutant, apum5-D, was isolated during a T-DNA insertional mutant screen for mutants with reduced susceptibility to Cucumber mosaic virus (CMV) infection. Interestingly, CMV RNA contained putative Pumilio-homology domain binding motifs in its 3' untranslated region (UTR) and internal places in its genome. APUM5 directly bound to the 3' UTR motifs and some internal binding motifs in CMV RNAs in vitro and in vivo. We showed that APUM5 acts as a translational repressor that regulates the 3' UTR of CMV and affects CMV replication. This study uncovered a unique defense system that Arabidopsis APUM5 specifically regulates CMV infection by the direct binding of CMV RNAs.

Improved Resistance to Cucumber mosaic virus in Petunia Transformed with Non‐Cytotoxic Pokeweed Antiviral Protein Gene

AbstractPetunia hybrida is an important ornamental plant that can be seriously affected by cucumber mosaic virus (CMV). Pokeweed antiviral protein (PAP), a ribosome‐inactivating protein, has been recognized as a broad spectrum virus inhibitory agent. Mutant PAP efficiently inhibited viral gene expression at both the translational and transcriptional levels without causing host cell toxicity. We have transferred the non‐cytotoxic pokeweed antiviral protein (mutant PAP) gene into petunia cells with Agrobacterium tumefaciens. Forty‐two putative transgenic regenerated lines were obtained from the selected explants. Fifty‐six plants immune to CMV infection were recovered from nine transgenic lines. Another 51 plants tolerant to CMV were obtained from 10 transgenic regenerated lines. Successful integration of the mutant PAP gene into the genome of transgenic petunia was confirmed by PCR and Southern blot analysis. Expression of the PAP gene was further confirmed by RT‐PCR and Western blot analysis. These results were consistent with the assay of resistance to CMV.

A Tobacco CBL-Interacting Protein Kinase Homolog Is Involved in Phosphorylation of the N-Terminal Domain of the Cucumber Mosaic Virus Polymerase 2a Protein

The replication and transcription of cucumber mosaic virus (CMV) are catalyzed by multi-protein complex RNA-dependent RNA polymerase (RdRp), which is composed of the viral-encoded 1a and 2a proteins with host factors. We have reported that the N-terminal region of the polymerase 2a protein, composed of 126 amino acids, is required for interaction with the helicase 1a protein, and that the phosphorylation of the region abrogated interaction with the 1a protein, suggesting a mechanism of resistance in host plants against viral infection. Here, we found that three protein 2a kinases, of 60, 55, and 38 kDa, co-purified with the tobacco membrane fraction in an in-gel kinase assay. By yeast two-hybrid library screening using the N-terminal 126 amino acids of 2a as a bait, we identified CBL-interacting protein kinase 12 (NtCIPK12) corresponding to 55 kDa protein 2a kinase. The bacterially expressed protein kinase showed protein 2a kinase (t2aK) activity in vitro. We found that NtCIPK12 stabilized upon CMV infection at the post-translational level, and accumulated more heavily to the membrane than in the cytosol.

Effects of Cucumber mosaic virus on the yield and yield components of peanut.

In Argentina, peanut (Arachis hypogaea) is naturally infected by Cucumber mosaic virus (CMV), subgroup II. The study involved the evaluation of the effects on yield and yield components in response to CMV infection at different growth stages: 4-6 developed nodes on the main axis (V4-6), 12-16 developed nodes on the main axis (V12-16) and onset of bloom (R1). The results showed that CMV infection significantly reduces peanut seed yield, mainly due to a severe decrease in seed average weight which declined approximately by 30%, 20% and 11% when the virus was inoculated at V4-6, V12- 16 and R1, respectively. The number of pods, seeds, and seeds per pod were affected only when the virus was inoculated at V4-6. The percentage of confectionery peanut was also significantly affected when CMV was inoculated at vegetative crop stages. In addition, seed size and weight/volume ratio were greatly affected by the virus since the infected plants produced a higher proportion of small seeds. Larger seeds decreased when the plants were infected at earlier growth stages. Finally, infected plants produced a significantly greater number of immature pods than the healthy ones.

First Report of Cucumber mosaic virus Infecting Watermelon in Serbia.

In June 2012, field-grown watermelon plants (Citrullus lanatus L.) with virus-like symptoms were observed in Silbaš locality, South Backa District of Serbia. Plants infected early in the growing season showed severe symptoms including stunting, mosaic, mottling, blistering, and leaf curling with reduced leaf size, while those infected at later stages exhibited only a mild mosaic. Affected plants were spread across the field and disease incidence was estimated at 40%. Thirteen symptomatic watermelon plants were sampled and analyzed by double-antibody sandwich (DAS)-ELISA using a commercial diagnostic kit (Bioreba AG, Reinach, Switzerland) against the most important watermelon viruses: Cucumber mosaic virus (CMV), Watermelon mosaic virus (WMV), Zucchini yellow mosaic virus (ZYMV), Papaya ringspot virus (PRSV), and Squash mosaic virus (SqMV) (1). Commercial positive and negative controls and an extract from healthy watermelon tissue were included in each ELISA. Serological analyses showed that all plants were positive for CMV and negative for ZYMV, WMV, PRSV, and SqMV. The virus was mechanically transmitted from an ELISA-positive sample (449-12) to five plants of each Citrullus lanatus 'Creamson sweet' and Chenopodium amaranticolor using 0.01 M phosphate buffer (pH 7) with Serbian CMV isolate from Cucurbita pepo 'Olinka' (GenBank Accession No. HM065510) and healthy watermelon plants as positive and negative controls, respectively. Small necrotic lesions on C. amaranticolor and mild mosaic with dark green vein banding on watermelon leaves were observed on all inoculated plants 5 and 14 days post-inoculation, respectively. For further confirmation of CMV infection, reverse transcription (RT)-PCR was performed with the One-Step RT-PCR Kit (Qiagen, Hilden, Germany) using specific primers CMVCPfwd (5'-TGCTTCTCCRCGARWTTGCGT-3') and CMVCPrev (5'-CGTAGCTGGATGGACAACCCG-3'), designed to amplify an 871-bp fragment of the RNA3 including the whole CP gene. Total RNA from 12 naturally infected and five mechanically infected watermelon plants was extracted with the RNease Plant Mini Kit (Qiagen). Total RNA obtained from the Serbian CMV isolate (HM065510) and healthy watermelon plants were used as positive and negative controls, respectively. The expected size of RT-PCR products were amplified from all naturally and mechanically infected watermelon plants but not from healthy tissues. The PCR product derived from isolate 449-12 was purified and directly sequenced using the same primer pair as in RT-PCR (JX280942) and analyzed by MEGA5 software (3). Sequence comparison of the complete CP gene (657 nt) revealed that the Serbian isolate 449-12 shared the highest nucleotide identity of 98.9% (99.1% amino acid identity) with the Spanish melon isolate (AJ829777) and Syrian tomato isolate (AB448696). To our knowledge, this is the first report of CMV on watermelon in Serbia. CMV is widely distributed within the Mediterranean basin where it has a substantial impact on many agricultural crops (2) and is often found to be prevalent during pumpkin and squash surveys in Serbia (4). The presence of CMV on watermelon could therefore represent a serious threat to this valuable crop in Serbia.

A viralRNAsilencing suppressor interferes with abscisic acid‐mediated signalling and induces drought tolerance inArabidopsis thaliana

Cucumber mosaic virus (CMV) encodes the 2b protein, which plays a role in local and systemic virus movement, symptom induction and suppression of RNA silencing. It also disrupts signalling regulated by salicylic acid and jasmonic acid. CMV induced an increase in tolerance to drought in Arabidopsis thaliana. This was caused by the 2b protein, as transgenic plants expressing this viral factor showed increased drought tolerance, but plants infected with CMVΔ2b, a viral mutant lacking the 2b gene, did not. The silencing effector ARGONAUTE1 (AGO1) controls a microRNA-mediated drought tolerance mechanism and, in this study, we noted that plants (dcl2/3/4 triple mutants) lacking functional short-interfering RNA-mediated silencing were also drought tolerant. However, drought tolerance engendered by CMV may be independent of the silencing suppressor activity of the 2b protein. Although CMV infection did not alter the accumulation of the drought response hormone abscisic acid (ABA), 2b-transgenic and ago1-mutant seeds were hypersensitive to ABA-mediated inhibition of germination. However, the induction of ABA-regulated genes in 2b-transgenic and CMV-infected plants was inhibited more strongly than in ago1-mutant plants. The virus engenders drought tolerance by altering the characteristics of the roots and not of the aerial tissues as, compared with the leaves of silencing mutants, leaves excised from CMV-infected or 2b-transgenic plants showed greater stomatal permeability and lost water more rapidly. This further indicates that CMV-induced drought tolerance is not mediated via a change in the silencing-regulated drought response mechanism. Under natural conditions, virus-induced drought tolerance may serve viruses by aiding susceptible hosts to survive periods of environmental stress.

Serological detection of Cucumber mosaic virus on some important host crops in the north region of Iran

Plant virus diseases cause major losses in agricultural and horticultural products, especially in tropical and subtropical regions. The first step to manage these diseases is detecting, identifying and determining the pathogen characteristics. Cucumber mosaic disease is one of the most prevalent and damaging plant diseases in the world which is caused by Cucumber mosaic virus (CMV). Each year, this virus causes yield decreasing and substantial economic damages in its host plants worldwide including the north of Iran. In order to study and identify CMV, 935 leaf samples were collected based on typical symptoms from 10 crops (tomato, pea, tobacco, soybean, watermelon, broad bean, squash, cucumber, eggplant and lettuce) in different regions of Golestan and Mazandaran provinces (north of Iran) during 2009–2010. Suspicious samples were analysed by DAS-ELISA and polyclonal antibodies. The results showed that 275 samples (29.4%) were infected by CMV. Between these hosts, the highest and the lowest CMV infection was associated to watermelon (62.44%) and lettuce (0%), respectively. Among sampling locations, Behshahr (100%) and Minoodasht (3.47%) showed the maximum and minimum infection, respectively.

Odontonema cuspidatum and Psychotria punctata, Two New Hosts of Cucumber mosaic virus in the United States.

Cucumber mosaic virus (CMV) has a reported host range of 750 to 1,200 species (2,3) that includes weeds, wild plants, crops, and ornamentals. Two new CMV hosts were recently identified in Florida. In July 2011, leaves of Odontonema cuspidatum (firespike), a member of the Acanthaceae, with virus-like symptoms were sent to FDACS-DPI. Firespike is an ornamental shrub native to Mexico with evergreen ovate leaves tapering to a pointed tip. Leaf symptoms included severe leaf distortion with some subtle yellowing or mosaic on younger leaves. Pink-red crystals were seen in leaf strips stained with the nucleic acid stain Azure A, indicating a viral infection. In January 2012, leaves of Psychotria punctata (dotted wild coffee), a member of the Rubiaceae, with virus-like symptoms were sent to FDACS-DPI. Dotted wild coffee is a small exotic tropical tree found in south Florida with many tiny leaf nodules inhabited by endosymbiotic bacteria. In addition to the nodules, these leaves had many large dark green ringspots surrounded with a yellow halo. Both samples were positive for CMV when tested with ImmunoStrips and/or by conventional ELISA using CMV antiserum (Agdia, Elkhart, IN). To confirm CMV infection, reverse transcriptase (RT)-PCR on total RNA from a leaf sample of each plant species was used with previously published cucumovirus primers (1). An expected ~940 bp product was amplified from each sample and cloned into pGEM-T (Promega, Madison, WI). Ten clones from each plant species were sequenced in both directions. After removal of primer sequences, the 906 bp products were 96.3% identical with each other and showed 96.8 to 98.9% nucleotide identity with CMV sequences from Hungary, the United States, and Austria (GenBank Accession Nos. AF517802, U20668, and HQ916354, respectively). Identification of CMV infection in these two species expands the known host range and therefore the reservoir of this plant virus. This has implications for the ornamental industry in general and Florida farmers in particular.

Characterization of a Novel Cucumber mosaic virus Isolated from Petunia hybrida

Petunia hybrida is commonly used in landscapes and interiors for its attractive flower. Virus-like foliar symptoms, including a mosaic with dark green islands surrounding the veins and chlorosis on the leaf margins, were observed on a petunia plant from Icheon, Gyeonggido, Korea. Cucumber mosaic virus (CMV) was identified in the symptomatic petunia by serological testing for the presence of CMV coat protein (CP) with a direct antibody-sandwich-enzyme-linked immunosorbent assay. An agent was mechanically transmitted to indicator plant species including Chenopodium quinoa. Examination of the inoculated plant leaves by RT-PCR analysis and electron microscopy revealed the presence of specifically amplified CP products and spherical virions of approximately 28 nm in diameter, respectively, providing confirmation of a CMV infection. Analysis of CP sequences showed that CMV petunia isolate (CMVYJC) shared 82.5-100% amino acid sequence identity with CPs of representative CMV strains. Phylogenetic analysis of CPs supports that CMV-YJC is a member of CMV subgroup IA (CMV-IA) and has biological properties of CMV-IA on host species. To our knowledge, this is the first report of CMV from P. hybrida in Korea.