Cucumber Mosaic Virus Infected Plants Research Articles

Plant viruses induce plant volatiles that are detected by aphid parasitoids

Aphis gossypii (Sternorrhyncha: Aphididae) aphids are vectors of important plant viruses among which cucumber mosaic virus (CMV) and potato virus Y (PVY). Virus-infected plants attract aphid vectors and affect their behavior and growth performance either positively or negatively depending on mode of transmission. Viruses cause changes in the composition and the amount of volatile organic compounds (VOCs) released by the plant that attract aphids. The aphid parasitoid Aphidius colemani (Hymenoptera: Aphelinidae) has been shown to have higher parasitism and survival rates on aphids fed on virus-infected than aphids fed on non-infected plants. We hypothesized that parasitoids distinguish virus-infected plants and are attracted to them regardless of the presence of their aphid hosts. Herein, we examined the attraction of the A. colemani parasitoid to infected pepper plants with each of CMV or PVY without the presence of aphids. The dynamic headspace technique was used to collect VOCs from non-infected and CMV or PVY-infected pepper plants. Identification was performed with gas chromatography-mass spectrometry (GC–MS). The response of the parasitoids on virus-infected vs non-infected pepper plants was tested by Y-tube olfactometer assays. The results revealed that parasitoids displayed a preference to CMV and PVY infected plants compared to those that were not infected.

Induction of resistance to Myzus persicae-nicotianae in Cucumber mosaic virus infected tobacco plants using silencing of CMV-2b gene

Aphids such as tobacco aphid Myzus persicae-nicotianae, are among the most important plant viral vectors and plant viruses encode genes to interact with their vectors. Cucumber mosaic virus (CMV) encodes 2b protein as a suppressor of plant immune and it plays a vital role in CMV accumulation and susceptibility to aphid vectors. In this study, the resistance of tobacco plants (Nicotiana tabacum) to M. p. nicotianae was evaluated by silencing of 2b in CMV-infected plants. However, the pFGC-C.h silencing gene construct was transiently expressed using Agrobacterium tumefacience, LBA 4404 in tobacco leaves, and four days later, the plants were mechanically inoculated by CMV (Kurdistan isolate), and then, 15 days post-inoculation 1 nonviruliferous aphid was placed on each leaf for evaluation of resistance to M. p. nicotianae. To evaluate the tobacco plants resistance and susceptibility to M. p. nicotianae, the number of aphids existent per tobacco leaf, life table and, demographic parameters were recorded and used as a comparison indicator. The obtained results were analyzed using the age-stage, two-sex life table. The highest number of aphids was recorded on the control CMV-infected plants, while the lowest number on CMV infected leaves expressing CMV-2b silencing construct (pFGC-C.h). The obtained data revealed the lowest rate for all of intrinsic rate of natural increase (rm) (0.246/day), the rate of reproduction (r0) (17.04 females/generation), and finite rate of increase (λ) (1.279/day), on the pFGC-C.h treatment. The maximum generation time (T) (11.834 days) was observed on (V) treatment. However, the collected data revealed induction of resistance to tobacco aphids by silencing of CMV-2b in CMV infected plants.

Effects of Cucumber Mosaic Virus on Cellular Components, Host Physiology and Yield of Chilli

Alteration of cellular components and host physiology due to five biotypes of Cucumber mosaic virus (CMV) were investigated to know the effects on ultimate growth and yield of chilli. Severe reduction of cellular components like chlorophyll-a (59.31%), chlorophyll-b (68.40%), total chlorophyll (63.20%) and β-carotene (51.14%) were observed in plant infected by mosaic and stunting (MoS) as compared to healthy plant. The ratio of RNA to DNA was increased in the infected leaves. The reduction of photosynthesis rate was found 6.32 to 17.10% in CMV infected plants as compared to healthy plants. Stomatal conductance and inter cellular CO2 was found lower in CMV infected plats. Considerable yield reduction (28.80 to 78.11%.) was found infected with five symptomatic isolate of CMV. The present findings indicate that multiplication of virus particles in the infected cells alter the biochemical compounds of cells that disrupt the physiological process which affect the growth and yield of chilli.

Aphid-borne Viral Spread Is Enhanced by Virus-induced Accumulation of Plant Reactive Oxygen Species.

Most known plant viruses are spread from plant to plant by insect vectors. There is strong evidence that nonpersistently transmitted viruses manipulate the release of plant volatiles to attract insect vectors, thereby promoting virus spread. The mechanisms whereby aphid settling and feeding is altered on plants infected with these viruses, however, are unclear. Here we employed loss-of-function mutations in cucumber mosaic virus (CMV) and one of its host plants, tobacco (Nicotiana tabacum), to elucidate such mechanisms. We show that, relative to a CMVΔ2b strain with a deletion of the viral suppressor of RNAi 2b protein in CMV, plants infected with wild-type CMV produce higher concentrations of the reactive oxygen species (ROS) H2O2 in plant tissues. Aphids on wild-type CMV-infected plants engage in shorter probes, less phloem feeding, and exhibit other changes, as detected by electrical penetration graphing technology, relative to CMVΔ2b-infected plants. Therefore, the frequency of virus acquisition and the virus load per aphid were greater on CMV-infected plants than on CMVΔ2b-infected plants. Aphids also moved away from initial feeding sites more frequently on wild-type CMV infected versus CMVΔ2b-infected plants. The role of H2O2 in eliciting these effects on aphids was corroborated using healthy plants infused with H2O2 Finally, H2O2 levels were not elevated, and aphid behavior was unchanged, on CMV-infected RbohD-silenced tobacco plants, which are deficient in the induction of ROS production. These results suggest that CMV uses its viral suppressor of RNAi protein to increase plant ROS levels, thereby enhancing its acquisition and transmission by vector insects.

Movement Protein of Cucumber Mosaic Virus Associates with Apoplastic Ascorbate Oxidase.

Plant viral movement proteins facilitate virion movement mainly through interaction with a number of factors from the host. We report the association of a cell wall localized ascorbate oxidase (CsAO4) from Cucumis sativus with the movement protein (MP) of Cucumber mosaic virus (CMV). This was identified first in a yeast two-hybrid screen and validated by in vivo pull down and bimolecular fluorescence complementation (BiFC) assays. The BiFC assay showed localization of the bimolecular complexes of these proteins around the cell wall periphery as punctate spots. The expression of CsAO4 was induced during the initial infection period (up to 72 h) in CMV infected Nicotiana benthamiana plants. To functionally validate its role in viral spread, we analyzed the virus accumulation in CsAO4 overexpressing Arabidopsis thaliana and transiently silenced N. benthamiana plants (through a Tobacco rattle virus vector). Overexpression had no evident effect on virus accumulation in upper non-inoculated leaves of transgenic lines in comparison to WT plants at 7 days post inoculation (dpi). However, knockdown resulted in reduced CMV accumulation in systemic (non-inoculated) leaves of NbΔAO-pTRV2 silenced plants as compared to TRV inoculated control plants at 5 dpi (up to 1.3 fold difference). In addition, functional validation supported the importance of AO in plant development. These findings suggest that AO and viral MP interaction helps in early viral movement; however, it had no major effect on viral accumulation after 7 dpi. This study suggests that initial induction of expression of AO on virus infection and its association with viral MP helps both towards targeting of the MP to the apoplast and disrupting formation of functional AO dimers for spread of virus to nearby cells, reducing the redox defense of the plant during initial stages of infection.

Paenibacillus lentimorbus Inoculation Enhances Tobacco Growth and Extenuates the Virulence of Cucumber mosaic virus.

Previous studies with Paenibacillus lentimorbus B-30488” (hereafter referred as B-30488), a plant growth promoting rhizobacteria (PGPR) isolated from cow’s milk, revealed its capabilities to improve plant quality under normal and stress conditions. Present study investigates its potential as a biocontrol agent against an economically important virus, Cucumber mosaic virus (CMV), in Nicotiana tabacum cv. White Burley plants and delineates the physical, biophysical, biochemical and molecular perturbations due to the trilateral interactions of PGPR-host-CMV. Soil inoculation of B-30488 enhanced the plant vigor while significantly decreased the virulence and virus RNA accumulation by ~12 fold (91%) in systemic leaves of CMV infected tobacco plants as compared to the control ones. Histology of these leaves revealed the improved tissue’s health and least aging signs in B-30488 inoculated tobacco plants, with or without CMV infection, and showed lesser intercellular spaces between collenchyma cells, reduced amount of xyloglucans and pectins in connecting primary cells, and higher polyphenol accumulation in hypodermis layer extending to collenchyma cells. B-30488 inoculation has favorably maneuvered the essential biophysical (ion leakage and photosynthetic efficiency) and biochemical (sugar, proline, chlorophyll, malondialdehyde, acid phosphatase and alkaline phosphatase) attributes of tobacco plants to positively regulate and release the virus stress. Moreover, activities of defense related enzymes (ascorbate peroxidase, guaiacol peroxidase, superoxide dismutase and catalase) induced due to CMV-infection were ameliorated with inoculation of B-30488, suggesting systemic induced resistance mediated protection against CMV in tobacco. The quantitative RT-PCR analyses of the genes related to normal plant development, stress and pathogenesis also corroborate well with the biochemical data and revealed the regulation (either up or down) of these genes in favor of plant to combat the CMV mediated stress. These improvements led tobacco plant to produce more flowers and seeds with no negative impact on plant health. The present study may advocate the applicability of B-30488 for crop yield improvement in virus infested areas.

First Report of Cucumber mosaic virus in Taro Plants in China.

Taro (Colocasia esculenta L. Schott) is an important crop worldwide. In China, the growing area and productivity of taro increased greatly in recent years. During the 2010 to 2013 growing seasons (from May to July), the incidence of Cucumber mosaic virus (CMV) in taro was determined. Leaf samples from 91 taro plants, including 26 plants of cv. Hongyayu grown in Jiangxi Province in eastern China, 33 plants of cv. Eyu no.1 grown in Hubei Province in central China, and 32 plants of cv. Baiyu grown in Guangxi Province in southwest China were collected randomly and tested for the presence of CMV by reverse transcription (RT)-PCR. Some sampled plants of cv. Hongyayu and Eyu no.1 showed leaf chlorosis or chlorotic spots, and most of the plants of these three cultivars showed feather-like mosaic symptom on their leaves, which was confirmed to be associated with the infection of Dasheen mosaic virus (DsMV) in our previous studies (3). Total RNA was extracted from leaves using CTAB protocol reported by Li et al. (1). Primer set forward 5'-ATGGACAAATCTGAATCAACC-3'/reverse 5'-TAAGCTGGATGGACAACCCGT-3' (4) was used for the amplification of a 777-bp fragment, which contains the complete capsid protein (CP) gene of 657 bp. PCR products of the expected size were identified from 11 taro samples, including two samples of Hongyayu, three Eyu no.1, and six Baiyu plants. The result did not show any specific association between the symptoms observed and CMV infection. The obtained PCR products were cloned individually into the vector pMD18-T (TaKaRa, Dalian, China). Three independent clones derived from each product were sequenced by Genscript Corp., Nanjing, China. Pairwise comparison of CP gene sequences (Accession No. of one representation CP sequence: KF564789) showed 99.7 to 99.8% nucleotide (nt) and 99.1 to 99.5% deduced amino acid (aa) sequence identity among themselves, and 92.0 to 94.3% and 76.5 to 77.7% nt identities with corresponding sequences of CMV isolates in subgroup I and subgroup II (2), respectively. The maximum likelihood phylogenetic trees of nt and aa sequences generated by Clustal X v1.8 revealed that all these CMV isolates from taro in China fell into subgroup I. To further confirm the CMV infection, leaf saps of CMV infected taro plants of cv. Eyu no.1 were mechanically inoculated onto Pinellia ternate and Cucumis sativus. Plants of P. ternate showed local chlorotic lesions on the inoculated leaves and downward curl of newly grown leaves, and C. sativus showed local chlorotic lesions on the inoculated leaves and crinkle of newly grown leaves at 10 to 15 days post inoculation. The RT-PCR detection confirmed the CMV infection in those inoculated plants, and that the plants of P. ternate were also positive to DsMV, further complementing the results obtained above. To our knowledge, this is the first report of CMV occurrence in taro plants grown in China. Our results indicated that taro plants were widely infected by CMV isolates in subgroup I. This study provides important information for further evaluating the viral sanitary status of taro germplasm and improving the certification program of taro propagation materials in China.

Behavior of RNAi suppressor protein 2b of Cucumber mosaic virus in planta in presence and absence of virus

The 2b protein encoded by Cucumber mosaic virus (CMV) has been shown as a virus counter defense factor that interferes with the RNAi pathway. The 2b gene from CMV-banana, New Delhi isolate (CMV-NDLS) was amplified from CMV infected cucumber plants to generate the sense and antisense binary vector constructs for 2b expression and repression in planta. Constitutive expression of 2b gene in healthy Nicotiana tabacum caused phenotypic aberrations during somatic embryogenesis, which were not observed when expressed in CMV infected N. tabacum. Further, the established virus population in CMV infected N. tabacum was not affected by constitutive expression and repression of 2b gene. Thus, indicating its role in initiation of gene silencing, at the early stage of viral infection. This is the first demonstration of differential behavior of 2b suppressor protein in host development in the absence and presence of virus.

Viral Suppression in Transgenic Plants Expressing Chimeric Transgene from Tomato Leaf Curl Virus and Cucumber Mosaic Virus

The genes CMV-cp and ToLCV-cons-rep from the isolates of cucumber mosaic virus (CMV) and tomato leaf curl virus (ToLCV) were transcriptionally fused under the control of CaMV 35 S promotor. This construct was used to transform tobacco and tomato using Agrobacterium. We show transforming ToLCV and CMV infected plants with the homologous chimeric gene construct, that produces RNAs, capable of duplex formation, confers gene silencing. We proposed that the antisense suppression in ToLCV infected plants provides a threshold level of dsRNA needed to induce gene silencing where as sense suppression in CMV infected plants may be operating through cosuppression, leading to delayed and attenuated symptoms.

Complementary DNA Hybridization Analysis of Double‐stranded RNAs Associated with Cucumber Mosaic Virus‐As Strain

AbstractVirus‐specific double‐stranded (ds) RNAs were isolated from leaves of Nicotiana tabacum cv. Xanthi‐nc infected with the As or Y strains of cucumber mosaic virus (CMV). These dsRNAs on agarose gels produced 5 bands corresponding, respectively to three genomic RNAs (dsRNAI, −2, −3), the subgenomic mRNA for coat protein (dsRNA4). and satellite dsRNA (dsRNA5) with estimated molecular weights of respectively, 2.5, 2.4, 1.45, 0.69 and 0.28 × 103 kD. In northern‐blot analysis, a 1 kbp complementary DNA (cDNA) to CMV‐As RNA4 hybridized strongly with dsRNA3 and dsRNA4 extracted from CMV‐As infected tobacco, but did not hybridize with dsRNAI, dsRNA2, or satellite dsRNA (dsRNA5). In slot‐blot analysis, the cDNA hybridized strongly with virus‐,specific dsRNAs isolated from CMV infected plants, but not with dsRNAs of TMV‐Korean common, potato virus Y‐VN, or total RNA of healthy tobacco plants.

Bright yellow chlorosis by cucumber mosaic virus Y satellite RNA is specifically induced without severe chloroplast damage

We have analysed morphological and physiological changes of the chloroplasts in tobacco plants infected with cucumber mosaic virus (CMV) Y satellite RNA (Y-satRNA). The infected tissues were bright yellow. Although the chlorophyll content of the tobacco plants infected with CMV-O + Y-satRNA was reduced to one-third to one-quarter of that of CMV infected and healthy tobacco plants, the chloroplasts in the Y-satRNA-infected leaves were ultrastructurally similar to those in the plants infected with only CMV-O. There were no significant differences in lipid content or composition of the chloroplast membrane between Y-satRNA-infected and CMV-O infected leaves. While the levels of all the stroma proteins were equivalent, the overall thylakoid proteins were decreased in the Y-satRNA-infected tissue compared with the CMV infected tissue. Chlorosis induced by Y-satRNA appears to result in the reduction of the chlorophyll-binding proteins. However, the photosynthetic ability of the chloroplasts from Y-satRNA infected leaves was greater than that of chloroplasts from CMV-O infected leaves. The possibility that chlorosis induced by Y-satRNA may be due to specific inhibition of chlorophyll accumulation rather than to chloroplast degradation is discussed in this paper.

Effects of Certain Systemic Insecticides on Gladiolus Growth and Spike Production1

Data were collected to determine effects of certain systemic insecticides on gladiolus growth. No significant differences were detected in plant emergence or height 17 and 23 days, respectively, after planting. At peak bloom, granular soil treatments of aldicarb, oxamyl, and disulfoton showed significant positive effects on gladiolus growth, as indicated by plant heights, flowerhead lengths, and bud numbers. Cucumber mosaic virus-infected plants in aldicarb and disulfoton-treated plots also showed growth benefits. No significant differences in corm weights were detected between treatments.