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Na-sheng Lin - One of the best experts on this subject based on the ideXlab platform.

  • Phylogeography and Coevolution of Bamboo Mosaic Virus and Its Associated Satellite RNA
    Frontiers Media S.A., 2017
    Co-Authors: Ingnang Wang, Wen-bin Yeh, Na-sheng Lin
    Abstract:

    Bamboo mosaic virus (BaMV), a plant potexvirus, has been found only in infected bamboo species. It is frequently associated with a large, linear single-stranded Satellite RNA (satBaMV) that encodes a non-structural protein. Decades of collecting across a wide geographic area in Asia have accumulated a sizable number of BaMV and satBaMV isolates. In this study, we reconstructed the BaMV phylogeny and satBaMV phylogeny with partial coat protein gene sequences and partial genomic sequences, respectively. The evolutionary relationships allowed us to infer the phylogeography of BaMV and satBaMV on the Asian continent and its outlying islands. The BaMV phylogeny suggests that the BaMV isolates from Taiwan, unsurprisingly, are most likely derived from China. Interestingly, the newly available satBaMV isolates from China were found to be most closely related to the previously established Clade III, which is found in India. The general pattern of clustering along the China/India and Taiwan divide led us to hypothesize that the Taiwan Strait has been a physical barrier to gene flow in the past evolutionary history of both BaMV and satBaMV. Lastly, cophylogeny analyses revealed a complex association pattern between BaMV and satBaMV isolates from China. In general, closely related BaMV sequences tend to carry closely related satBaMV sequences as well; but instances of mismatching with distantly related satBaMV isolates were also found. We hypothesize plausible scenarios of infection and superinfection of bamboo hosts that may be responsible for the observed association pattern. However, a more systematic sampling throughout the geographic distribution of various bamboo species is needed to unambiguously establish the origin, movement, and evolution of BaMV and satBaMV

  • transgenic resistance to bamboo mosaic virus by expression of interfering Satellite RNA
    Molecular Plant Pathology, 2013
    Co-Authors: Na-sheng Lin, Yau-heiu Hsu, Kuanyu Lin, Hsinchuan Chen
    Abstract:

    Summary Plant genetic engineering has broadened the options for plant virus resistance and is mostly based on pathogen-derived resistance. Previously, we have shown that interfering Satellite RNA (satRNA) of Bamboo mosaic virus (satBaMV) greatly reduces Bamboo mosaic virus (BaMV) accumulation and BaMV-induced symptoms in co-inoculated plants. Here, we generated a nonviral source of virus-resistant transgenic Nicotiana benthamiana and Arabidopsis thaliana by introducing interfering satBaMV. Asymptomatic transgenic N. benthamiana lines were highly resistant to BaMV virion and viral RNA infection, and the expression of the transgene BSL6 was higher in asymptomatic than mildly symptomatic lines. In addition, BaMV- and satBaMV-specific small RNAs were detectable only after BaMV challenge, and their levels were associated with genomic viral RNA or satRNA levels. By transcriptomic analysis, the salicylic acid (SA) signalling pathway was not induced in satBaMV transgenic A. thaliana in mock conditions, suggesting that two major antiviral mechanisms, RNA silencing and SA-mediated resistance, are not involved directly in transgenic satBaMV-mediated BaMV interference. In contrast, resistance is associated with the level of the interfering satBaMV transgene. We propose satBaMV-mediated BaMV interference in transgenic plants by competition for replicase with BaMV.

  • hsp90 interacts specifically with viral RNA and differentially regulates replication initiation of bamboo mosaic virus and associated Satellite RNA
    PLOS Pathogens, 2012
    Co-Authors: Ying-wen Huang, Chinghsiu Tsai, Menghsiao Meng, Na-sheng Lin, Banyang Chang, Mingru Liou, Yau-heiu Hsu
    Abstract:

    Host factors play crucial roles in the replication of plus-strand RNA viruses. In this report, a heat shock protein 90 homologue of Nicotiana benthamiana, NbHsp90, was identified in association with partially purified replicase complexes from BaMV-infected tissue, and shown to specifically interact with the 3′ untranslated region (3′ UTR) of BaMV genomic RNA, but not with the 3′ UTR of BaMV-associated Satellite RNA (satBaMV RNA) or that of genomic RNA of other viruses, such as Potato virus X (PVX) or Cucumber mosaic virus (CMV). Mutational analyses revealed that the interaction occurs between the middle domain of NbHsp90 and domain E of the BaMV 3′ UTR. The knockdown or inhibition of NbHsp90 suppressed BaMV infectivity, but not that of satBaMV RNA, PVX, or CMV in N. benthamiana. Time-course analysis further revealed that the inhibitory effect of 17-AAG is significant only during the immediate early stages of BaMV replication. Moreover, yeast two-hybrid and GST pull-down assays demonstrated the existence of an interaction between NbHsp90 and the BaMV RNA-dependent RNA polymerase. These results reveal a novel role for NbHsp90 in the selective enhancement of BaMV replication, most likely through direct interaction with the 3′ UTR of BaMV RNA during the initiation of BaMV RNA replication.

  • phosphorylation of bamboo mosaic virus Satellite RNA satbamv encoded protein p20 downregulates the formation of satbamv p20 ribonucleoprotein complex
    Nucleic Acids Research, 2012
    Co-Authors: Paramasivan Vijayapalani, Yau-heiu Hsu, Hsinchuan Chen, Mingru Liou, Jeff C F Chen, Na-sheng Lin
    Abstract:

    Bamboo mosaic virus (BaMV) Satellite RNA (satBaMV) depends on BaMV for its replication and encapsidation. SatBaMV-encoded P20 protein is an RNA-binding protein that facilitates satBaMV systemic movement in co-infected plants. Here, we examined phosphorylation of P20 and its regulatory functions. Recombinant P20 (rP20) was phosphorylated by host cellular kinase(s) in vitro, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and mutational analyses revealed Ser-11 as the phosphorylation site. The phosphor-mimic rP20 protein interactions with satBaMV-translated mutant P20 were affected. In overlay assay, the Asp mutation at S11 (S11D) completely abolished the self-interaction of rP20 and significantly inhibited the interaction with both the WT and S11A rP20. In chemical cross-linking assays, S11D failed to oligomerize. Electrophoretic mobility shift assay and subsequent Hill transformation analysis revealed a low affinity of the phospho-mimicking rP20 for satBaMV RNA. Substantial modulation of satBaMV RNA conformation upon interaction with nonphospho-mimic rP20 in circular dichroism analysis indicated formation of stable satBaMV ribonucleoprotein complexes. The dissimilar satBaMV translation regulation of the nonphospho- and phospho-mimic rP20 suggests that phosphorylation of P20 in the ribonucleoprotein complex converts the translation-incompetent satBaMV RNA to messenger RNA. The phospho-deficient or phospho-mimicking P20 mutant of satBaMV delayed the systemic spread of satBaMV in co-infected Nicotiana benthamiana with BaMV. Thus, satBaMV likely regulates the formation of satBaMV RNP complex during co-infection in planta.

  • structural and functional analyses of the 3 untranslated region of bamboo mosaic virus Satellite RNA
    Virology, 2009
    Co-Authors: Ying-wen Huang, Chinghsiu Tsai, Na-sheng Lin, Chihan Lin, Yuping Liu, Yau-heiu Hsu
    Abstract:

    The 3'-untranslated region (UTR) of RNA genomes of viruses and Satellite RNAs plays essential roles in viral replication and transcription. The structural features of the 3'-UTR of the Satellite RNA of Bamboo mosaic virus (satBaMV) involved in its replication were analyzed in this study. By the use of enzymatic probing, the secondary structure of satBaMV 3'-UTR was confirmed to comprise two small stem-loops (SLA and SLB), one large stem-loop (SLC), and a poly(A) tail of mainly 75-200 adenylate residues, which is similar to those on the genomic RNA of the helper virus, BaMV. Five sets of mutants of satBaMV were constructed to analyze the biological functions of the structural elements of the 3'-UTR. The data revealed that both the polyadenylation signal and poly(A) tail are required for satBaMV RNA replication. The structural conservation of SLA, SLB, and SLC is also important for efficient satBaMV accumulation, whereas the nucleotides in these regions may also possess sequence-specific functions. In contrast to the requirement for the accumulation of BaMV genomic RNA, mutations in the conserved hexanucleotide (ACCUAA) in the loop region of SLC had limited effect on the accumulation of satBaMV RNA. In addition, replacing the 5'-, 3'-UTR, or both regions of satBaMV by those of BaMV greatly decreased the accumulation of satBaMV RNA. Taken together, these data indicate that satBaMV might have adopted a 3'-UTR structure similar to that of BaMV but may have evolved distinct features for its efficient replication.

D J Robinson - One of the best experts on this subject based on the ideXlab platform.

  • Satellite RNA is essential for encapsidation of groundnut rosette umbravirus RNA by groundnut rosette assistor luteovirus coat protein
    Virology, 1999
    Co-Authors: D J Robinson, S K Raj, I M Roberts, Michael Taliansky
    Abstract:

    Abstract Groundnut rosette disease is caused by a complex of agents comprising groundnut rosette umbravirus (GRV), GRV Satellite RNA (sat-RNA)groundnut rosette assistor luteovirus (GRAV). Both GRAV and GRV sat-RNA are needed for GRV to be aphid transmissible. To understand the role of GRAVGRV sat-RNA in the aphid transmission of GRV, encapsidation of GRV genomicSatellite RNAs has been studied using transgenic Nicotiana benthamiana plants expressing GRAV coat protein (CP). GRAV CP expressed from a transgene was shown to package GRV genomicSatellite RNAs efficiently, giving a high yield of transcapsidated virus particles. GRV sat-RNA was absolutely essential for this process. GRV genomic RNA was not encapsidated by GRAV CP in the absence of the sat-RNA. Using different mutants of GRV sat-RNA, it was found that some property of full-length Satellite RNA molecules, such as size or specific conformation rather than potential open reading frames, was required for the production of virus particles. A correlation between the ability of sat-RNA to stimulate encapsidation of GRV RNA by GRAV CPits capacity to promote aphid transmission of GRV was observed.

  • two distinct mechanisms of transgenic resistance mediated by groundnut rosette virus Satellite RNA sequences
    Molecular Plant-microbe Interactions, 1998
    Co-Authors: Michael Taliansky, Eugene V Ryabov, D J Robinson
    Abstract:

    Transformation of Nicotiana benthamiana with full-length sequences of a mild variant of the groundnut rosette virus (GRV) Satellite RNA (sat-RNA) yielded plants that did not produce symptoms when inoculated with GRV and a virulent sat-RNA. Two different resistance mechanisms operated in different transformed lines. In the first, plants contained high levels of transcript RNA, and replication of both sat-RNA and GRV genomic RNA was inhibited. This mechanism is analogous to the down-regulation of GRV genomic and sat-RNA replication in infections containing the mild sat-RNA, and indeed infection of sat-RNA transgenic plants with GRV was shown to lead to liberation of unit-length sat-RNA from transgene transcripts. In the second resistance mechanism, plants contained low transcript RNA levels, and replication of sat-RNA but not of GRV genomic RNA was inhibited. These plants were also resistant to infection by potato virus X derivatives containing GRV sat-RNA sequences. This mechanism is an example of homology-dependent gene silencing or cosuppression. Resistant plants were also produced by transformation with sequences representing only the 5′ terminal one-third of the mild sat-RNA; the mechanism of resistance in these plants was of the cosuppression type. Additional keywords: groundnut rosette disease.

  • trans acting untranslated elements of groundnut rosette virus Satellite RNA are involved in symptom production
    Journal of General Virology, 1997
    Co-Authors: Michael Taliansky, D J Robinson
    Abstract:

    Isolates of groundnut rosette umbravirus (GRV) contain a Satellite RNA (sat-RNA), about 900 nucleotides (nt) in length, different variants of which are responsible for the symptoms of different forms of rosette disease in groundnuts and, in the particular instance of sat-RNA YB3b, for the production of yellow blotch symptoms in Nicotiana benthamiana. Sat-RNA YB3b does not affect the accumulation of GRV genomic or subgenomic RNAs in infected plants. Replication of sat-RNA YB3b and induction of yellow blotch symptoms do not require the production of any sat-RNA-encoded proteins. Experiments with deletion mutants identified three functional untranslated elements in sat-RNA YB3b. One (designated R) comprises nt 47-281, is essential for sat-RNA replication and appears to be cis-acting. The other two (designated A and B) comprise nt 280-470 and 629-849, respectively, are both involved in yellow blotch symptom production and can act in trans. Element A contains the determinant that is unique to sat-RNA YB3b. The process of symptom induction by sat-RNA YB3b apparently involves a novel type of specific interaction of two untranslated RNA elements, which can complement each other, with a host factor or factors.

  • down regulation of groundnut rosette virus replication by a variant Satellite RNA
    Virology, 1997
    Co-Authors: Michael Taliansky, D J Robinson
    Abstract:

    Symptom production in groundnut plants infected with groundnut rosette virus (GRV) depends on the presence of Satellite RNA (sat-RNA) in the GRV culture, and sat-RNA variants that induce only mild symptoms are known. One such variant drastically diminished the replication of GRV genomic RNA in infected Nicotiana benthamiana plants. This down-regulating ability did not involve either of the two open reading frames in the sat-RNA but was controlled by a region near its 5' end, which is required for sat-RNA replication. When N. benthamiana plants were inoculated with GRV and the mild Satellite and challenged by inoculation with a GRV isolate (YB) containing a sat-RNA that induces yellow blotch symptoms, no symptoms appeared and little GRV genomic RNA or sat-RNA was detected in the plants, provided the two inoculations were no more than 2 days apart. A GRV isolate containing a sat-RNA that neither induces symptoms in N. benthamiana nor affects genomic RNA accumulation also provided protection against yellow blotch symptom production if inoculated before or up to 2 days after isolate YB. However, in this case protection ws incomplete and both GRV RNA and sat-RNA accumulated to normal levels. It is suggested that sequences from the mild sat-RNA may provide a novel source of resistance against rosette disease.

  • detection of groundnut rosette umbravirus infections with radioactive and non radioactive probes to its Satellite RNA
    Annals of Applied Biology, 1995
    Co-Authors: V C Blok, D J Robinson, Angelika Ziegler, K Scott, D B Dangora, A F Murant
    Abstract:

    Summary A cloned cDNA copy of the Satellite RNA of groundnut rosette virus (GRV), labelled with either 32P or digoxigenin, was used as a probe to detect the Satellite RNA in infected leaves. The test was successfully applied to N. benthamiana and to groundnuts, infected with isolates of GRV from East and West Africa and with isolates which cause different types of symptom in groundnuts, including one which is almost symptomless. Although the probe did not react with extracts from plants infected with GRV isolates from which the Satellite RNA had been artificially eliminated, all naturally occurring GRV isolates contain the Satellite RNA. The test therefore provides a reliable indicator of infection by GRV.

Yau-heiu Hsu - One of the best experts on this subject based on the ideXlab platform.

  • transgenic resistance to bamboo mosaic virus by expression of interfering Satellite RNA
    Molecular Plant Pathology, 2013
    Co-Authors: Na-sheng Lin, Yau-heiu Hsu, Kuanyu Lin, Hsinchuan Chen
    Abstract:

    Summary Plant genetic engineering has broadened the options for plant virus resistance and is mostly based on pathogen-derived resistance. Previously, we have shown that interfering Satellite RNA (satRNA) of Bamboo mosaic virus (satBaMV) greatly reduces Bamboo mosaic virus (BaMV) accumulation and BaMV-induced symptoms in co-inoculated plants. Here, we generated a nonviral source of virus-resistant transgenic Nicotiana benthamiana and Arabidopsis thaliana by introducing interfering satBaMV. Asymptomatic transgenic N. benthamiana lines were highly resistant to BaMV virion and viral RNA infection, and the expression of the transgene BSL6 was higher in asymptomatic than mildly symptomatic lines. In addition, BaMV- and satBaMV-specific small RNAs were detectable only after BaMV challenge, and their levels were associated with genomic viral RNA or satRNA levels. By transcriptomic analysis, the salicylic acid (SA) signalling pathway was not induced in satBaMV transgenic A. thaliana in mock conditions, suggesting that two major antiviral mechanisms, RNA silencing and SA-mediated resistance, are not involved directly in transgenic satBaMV-mediated BaMV interference. In contrast, resistance is associated with the level of the interfering satBaMV transgene. We propose satBaMV-mediated BaMV interference in transgenic plants by competition for replicase with BaMV.

  • hsp90 interacts specifically with viral RNA and differentially regulates replication initiation of bamboo mosaic virus and associated Satellite RNA
    PLOS Pathogens, 2012
    Co-Authors: Ying-wen Huang, Chinghsiu Tsai, Menghsiao Meng, Na-sheng Lin, Banyang Chang, Mingru Liou, Yau-heiu Hsu
    Abstract:

    Host factors play crucial roles in the replication of plus-strand RNA viruses. In this report, a heat shock protein 90 homologue of Nicotiana benthamiana, NbHsp90, was identified in association with partially purified replicase complexes from BaMV-infected tissue, and shown to specifically interact with the 3′ untranslated region (3′ UTR) of BaMV genomic RNA, but not with the 3′ UTR of BaMV-associated Satellite RNA (satBaMV RNA) or that of genomic RNA of other viruses, such as Potato virus X (PVX) or Cucumber mosaic virus (CMV). Mutational analyses revealed that the interaction occurs between the middle domain of NbHsp90 and domain E of the BaMV 3′ UTR. The knockdown or inhibition of NbHsp90 suppressed BaMV infectivity, but not that of satBaMV RNA, PVX, or CMV in N. benthamiana. Time-course analysis further revealed that the inhibitory effect of 17-AAG is significant only during the immediate early stages of BaMV replication. Moreover, yeast two-hybrid and GST pull-down assays demonstrated the existence of an interaction between NbHsp90 and the BaMV RNA-dependent RNA polymerase. These results reveal a novel role for NbHsp90 in the selective enhancement of BaMV replication, most likely through direct interaction with the 3′ UTR of BaMV RNA during the initiation of BaMV RNA replication.

  • phosphorylation of bamboo mosaic virus Satellite RNA satbamv encoded protein p20 downregulates the formation of satbamv p20 ribonucleoprotein complex
    Nucleic Acids Research, 2012
    Co-Authors: Paramasivan Vijayapalani, Yau-heiu Hsu, Hsinchuan Chen, Mingru Liou, Jeff C F Chen, Na-sheng Lin
    Abstract:

    Bamboo mosaic virus (BaMV) Satellite RNA (satBaMV) depends on BaMV for its replication and encapsidation. SatBaMV-encoded P20 protein is an RNA-binding protein that facilitates satBaMV systemic movement in co-infected plants. Here, we examined phosphorylation of P20 and its regulatory functions. Recombinant P20 (rP20) was phosphorylated by host cellular kinase(s) in vitro, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and mutational analyses revealed Ser-11 as the phosphorylation site. The phosphor-mimic rP20 protein interactions with satBaMV-translated mutant P20 were affected. In overlay assay, the Asp mutation at S11 (S11D) completely abolished the self-interaction of rP20 and significantly inhibited the interaction with both the WT and S11A rP20. In chemical cross-linking assays, S11D failed to oligomerize. Electrophoretic mobility shift assay and subsequent Hill transformation analysis revealed a low affinity of the phospho-mimicking rP20 for satBaMV RNA. Substantial modulation of satBaMV RNA conformation upon interaction with nonphospho-mimic rP20 in circular dichroism analysis indicated formation of stable satBaMV ribonucleoprotein complexes. The dissimilar satBaMV translation regulation of the nonphospho- and phospho-mimic rP20 suggests that phosphorylation of P20 in the ribonucleoprotein complex converts the translation-incompetent satBaMV RNA to messenger RNA. The phospho-deficient or phospho-mimicking P20 mutant of satBaMV delayed the systemic spread of satBaMV in co-infected Nicotiana benthamiana with BaMV. Thus, satBaMV likely regulates the formation of satBaMV RNP complex during co-infection in planta.

  • structural and functional analyses of the 3 untranslated region of bamboo mosaic virus Satellite RNA
    Virology, 2009
    Co-Authors: Ying-wen Huang, Chinghsiu Tsai, Na-sheng Lin, Chihan Lin, Yuping Liu, Yau-heiu Hsu
    Abstract:

    The 3'-untranslated region (UTR) of RNA genomes of viruses and Satellite RNAs plays essential roles in viral replication and transcription. The structural features of the 3'-UTR of the Satellite RNA of Bamboo mosaic virus (satBaMV) involved in its replication were analyzed in this study. By the use of enzymatic probing, the secondary structure of satBaMV 3'-UTR was confirmed to comprise two small stem-loops (SLA and SLB), one large stem-loop (SLC), and a poly(A) tail of mainly 75-200 adenylate residues, which is similar to those on the genomic RNA of the helper virus, BaMV. Five sets of mutants of satBaMV were constructed to analyze the biological functions of the structural elements of the 3'-UTR. The data revealed that both the polyadenylation signal and poly(A) tail are required for satBaMV RNA replication. The structural conservation of SLA, SLB, and SLC is also important for efficient satBaMV accumulation, whereas the nucleotides in these regions may also possess sequence-specific functions. In contrast to the requirement for the accumulation of BaMV genomic RNA, mutations in the conserved hexanucleotide (ACCUAA) in the loop region of SLC had limited effect on the accumulation of satBaMV RNA. In addition, replacing the 5'-, 3'-UTR, or both regions of satBaMV by those of BaMV greatly decreased the accumulation of satBaMV RNA. Taken together, these data indicate that satBaMV might have adopted a 3'-UTR structure similar to that of BaMV but may have evolved distinct features for its efficient replication.

  • subcellular localization and expression of bamboo mosaic virus Satellite RNA encoded protein
    Journal of General Virology, 2009
    Co-Authors: Paramasivan Vijaya Palani, Yau-heiu Hsu, Chi Ping Cheng, Morgan Chiu, Wei Chen, Chingchi Wang, Choychieng Lin, Chuenchi Hsu, Chungmong Chen, Na-sheng Lin
    Abstract:

    The Satellite RNA of bamboo mosaic virus (satBaMV) has a single open reading frame encoding a non-structural protein, P20, which facilitates long-distance movement of satBaMV in BaMV and satBaMV co-infected plants. Immunohistochemistry and immunoelectron microscopy revealed that the P20 protein accumulated in the cytoplasm and nuclei in co-infected cells. P20 and the helper virus coat protein (CP) were highly similar in their subcellular localization, except that aggregates of BaMV virions were not labelled with anti-P20 serum. The BaMV CP protein was fairly abundant in mesophyll cells, whilst P20 was more frequently detected in mesophyll cells and vascular tissues. The expression kinetics of the P20 protein was similar to but slightly earlier than that of CP in co-infected Bambusa oldhamii protoplasts and Nicotiana benthamiana leaves. However, satBaMV-encoded protein levels declined rapidly in the late phase of co-infection. During co-infection, in addition to the intact P20, a low-molecular-mass polypeptide of 16 kDa was identified as a P20 C-terminally truncated product; the possible method of generation of the truncated protein is discussed.

Michael Taliansky - One of the best experts on this subject based on the ideXlab platform.

  • Satellite RNA is essential for encapsidation of groundnut rosette umbravirus RNA by groundnut rosette assistor luteovirus coat protein
    Virology, 1999
    Co-Authors: D J Robinson, S K Raj, I M Roberts, Michael Taliansky
    Abstract:

    Abstract Groundnut rosette disease is caused by a complex of agents comprising groundnut rosette umbravirus (GRV), GRV Satellite RNA (sat-RNA)groundnut rosette assistor luteovirus (GRAV). Both GRAV and GRV sat-RNA are needed for GRV to be aphid transmissible. To understand the role of GRAVGRV sat-RNA in the aphid transmission of GRV, encapsidation of GRV genomicSatellite RNAs has been studied using transgenic Nicotiana benthamiana plants expressing GRAV coat protein (CP). GRAV CP expressed from a transgene was shown to package GRV genomicSatellite RNAs efficiently, giving a high yield of transcapsidated virus particles. GRV sat-RNA was absolutely essential for this process. GRV genomic RNA was not encapsidated by GRAV CP in the absence of the sat-RNA. Using different mutants of GRV sat-RNA, it was found that some property of full-length Satellite RNA molecules, such as size or specific conformation rather than potential open reading frames, was required for the production of virus particles. A correlation between the ability of sat-RNA to stimulate encapsidation of GRV RNA by GRAV CPits capacity to promote aphid transmission of GRV was observed.

  • two distinct mechanisms of transgenic resistance mediated by groundnut rosette virus Satellite RNA sequences
    Molecular Plant-microbe Interactions, 1998
    Co-Authors: Michael Taliansky, Eugene V Ryabov, D J Robinson
    Abstract:

    Transformation of Nicotiana benthamiana with full-length sequences of a mild variant of the groundnut rosette virus (GRV) Satellite RNA (sat-RNA) yielded plants that did not produce symptoms when inoculated with GRV and a virulent sat-RNA. Two different resistance mechanisms operated in different transformed lines. In the first, plants contained high levels of transcript RNA, and replication of both sat-RNA and GRV genomic RNA was inhibited. This mechanism is analogous to the down-regulation of GRV genomic and sat-RNA replication in infections containing the mild sat-RNA, and indeed infection of sat-RNA transgenic plants with GRV was shown to lead to liberation of unit-length sat-RNA from transgene transcripts. In the second resistance mechanism, plants contained low transcript RNA levels, and replication of sat-RNA but not of GRV genomic RNA was inhibited. These plants were also resistant to infection by potato virus X derivatives containing GRV sat-RNA sequences. This mechanism is an example of homology-dependent gene silencing or cosuppression. Resistant plants were also produced by transformation with sequences representing only the 5′ terminal one-third of the mild sat-RNA; the mechanism of resistance in these plants was of the cosuppression type. Additional keywords: groundnut rosette disease.

  • trans acting untranslated elements of groundnut rosette virus Satellite RNA are involved in symptom production
    Journal of General Virology, 1997
    Co-Authors: Michael Taliansky, D J Robinson
    Abstract:

    Isolates of groundnut rosette umbravirus (GRV) contain a Satellite RNA (sat-RNA), about 900 nucleotides (nt) in length, different variants of which are responsible for the symptoms of different forms of rosette disease in groundnuts and, in the particular instance of sat-RNA YB3b, for the production of yellow blotch symptoms in Nicotiana benthamiana. Sat-RNA YB3b does not affect the accumulation of GRV genomic or subgenomic RNAs in infected plants. Replication of sat-RNA YB3b and induction of yellow blotch symptoms do not require the production of any sat-RNA-encoded proteins. Experiments with deletion mutants identified three functional untranslated elements in sat-RNA YB3b. One (designated R) comprises nt 47-281, is essential for sat-RNA replication and appears to be cis-acting. The other two (designated A and B) comprise nt 280-470 and 629-849, respectively, are both involved in yellow blotch symptom production and can act in trans. Element A contains the determinant that is unique to sat-RNA YB3b. The process of symptom induction by sat-RNA YB3b apparently involves a novel type of specific interaction of two untranslated RNA elements, which can complement each other, with a host factor or factors.

  • down regulation of groundnut rosette virus replication by a variant Satellite RNA
    Virology, 1997
    Co-Authors: Michael Taliansky, D J Robinson
    Abstract:

    Symptom production in groundnut plants infected with groundnut rosette virus (GRV) depends on the presence of Satellite RNA (sat-RNA) in the GRV culture, and sat-RNA variants that induce only mild symptoms are known. One such variant drastically diminished the replication of GRV genomic RNA in infected Nicotiana benthamiana plants. This down-regulating ability did not involve either of the two open reading frames in the sat-RNA but was controlled by a region near its 5' end, which is required for sat-RNA replication. When N. benthamiana plants were inoculated with GRV and the mild Satellite and challenged by inoculation with a GRV isolate (YB) containing a sat-RNA that induces yellow blotch symptoms, no symptoms appeared and little GRV genomic RNA or sat-RNA was detected in the plants, provided the two inoculations were no more than 2 days apart. A GRV isolate containing a sat-RNA that neither induces symptoms in N. benthamiana nor affects genomic RNA accumulation also provided protection against yellow blotch symptom production if inoculated before or up to 2 days after isolate YB. However, in this case protection ws incomplete and both GRV RNA and sat-RNA accumulated to normal levels. It is suggested that sequences from the mild sat-RNA may provide a novel source of resistance against rosette disease.

D Gallitelli - One of the best experts on this subject based on the ideXlab platform.

  • response of tomato and its wild relatives in the genus solanum to cucumber mosaic virus and Satellite RNA combinations
    Journal of General Virology, 2007
    Co-Authors: Fabrizio Cillo, M M Finettisialer, M M Pasciuto, C De Giovanni, Luigi Ricciardi, D Gallitelli
    Abstract:

    The differential response of 29 genotypes of tomato and wild tomato relatives (Solanum section Lycopersicon species) to cucumber mosaic virus strain Fny (CMV-Fny), alone or in combination with three different Satellite RNA (satRNA) variants, allowed the identification of four disease phenotype patterns, each including plants that developed very severe symptoms (leaf malformations, top stunting and lethal necrosis) and plants that remained asymptomatic. No resistance or tolerance to CMV-Fny was observed, whilst individual host genotypes displayed latent infection upon inoculation with one (CMV-Fny/Tfn-satRNA, phenotype patterns 1 and 4), two (CMV-Fny/Tfn-satRNA and CMV-Fny/TTS-satRNA, phenotype pattern 2) or all three (the former two plus CMV-Fny/77-satRNA, phenotype pattern 3) CMV/satRNA combinations. RNA gel-blot analyses showed that latent infection generally correlated with a strong downregulation of CMV RNA accumulation levels. Introgression lines derived from a cross between Solanum habrochaites LA1777, which displayed disease phenotype pattern 2, and Solanum lycopersicum were screened for tolerance to the stunting phenotype induced by CMV-Fny/TTS-satRNA, and only one line, carrying an introgression on chromosome 6, was identified as being partially tolerant. Solanum chilense LA1932xS. lycopersicum back-cross introgression lines were screened for tolerance to lethal necrosis induced by CMV-Fny/77-satRNA (phenotype pattern 3); the tolerant phenotype was observed in 33 % of plants of the BC(1)F(2) progeny and <1 % of plants of the BC(1)F(3) progeny. Thus, potentially useful sources of tolerance to CMV/satRNA-induced diseases were identified, although the tolerant phenotypes appeared to be controlled by complex quantitative trait loci.

  • analysis of mechanisms involved in the cucumber mosaic virus Satellite RNA mediated transgenic resistance in tomato plants
    Molecular Plant-microbe Interactions, 2004
    Co-Authors: Fabrizio Cillo, M M Finettisialer, Maria A Papanice, D Gallitelli
    Abstract:

    Transgenic tomato (Lycopersicon esculentum Mill. cv. UC82) plants expressing a benign variant of Cucumber mosaic virus Satellite RNA (CMV Tfn-satRNA) were generated. The transformed plants did not produce symptoms when challenged with a satRNA-free strain of CMV (CMV-FL). The same plant lines initially were susceptible to necrosis elicited by a CMV strain supporting a necrogenic variant of satRNA (CMV-77), but a phenotype of total recovery from the necrosis was observed in the newly developing leaves. The features of the observed resistance were analyzed and are consistent with two different mechanisms of resistance. In transgenic plants inoculated with CMV-FL strain, the symptomless phenotype was correlated to the down-regulation of CMV by Tfn-satRNA, amplified from the transgene transcripts, as the first resistance mechanism. On the other hand, the delayed resistance to CMV-77 in transgenic tomato lines was mediated by a degradation process that targets satRNAs in a sequence-specific manner. Evidence is provided for a correlation between a reduced accumulation level of transgenic messenger Tfn-satRNA, the accumulation of small (approximately 23 nucleotides) RNAs with sequence homology to satRNAs, the progressively reduced accumulation of 77-satRNA in infected tissues, and the transition in infected plants from diseased to healthy. Thus, events leading to the degradation of satRNA sequences indicate a role for RNA silencing as the second mechanism determining resistance of transgenic tomato lines.

  • evolutionary dynamics of cucumber mosaic virus Satellite RNA during natural epidemics in italy
    Virology, 1997
    Co-Authors: Francesco Grieco, C Lanave, D Gallitelli
    Abstract:

    The evolutionary dynamics of 22 variants of cucumber mosaic virus Satellite RNA (CMV satRNA) isolated in Italy during virus epidemics from 1988 to 1993 were investigated on the basis of their primary structure and biological properties. Most of the variants were amplified from total nucleic acid preparations extracted from field-infected plants, thus representing wild isolates of CMV satRNA. Eleven variants were associated with subgroup II CMV strains, 10 with subgroup I and 1 with a mixed infection by both strains. When inoculated onto tomato seedlings, the variants induced the phenotype (necrogenic or ameliorative) predicted by their nucleotide sequence. Phylogenetic relationships between the satRNA variants were determined using the stationary Markov model, a stochastic model for evolution. For each satRNA, the Markov analysis gave a good correlation between position in the phylogenetic tree and biological properties. The variants with ameliorative and necrogenic phenotypes in tomato followed two different evolutionary dynamics in nature. Tfn-satRNA, a 390-nt-long molecule, followed a third type of evolutionary dynamic far apart from that of the shorter satRNA molecules (i.e., those in the 334- to 340-nt-length class). Average values of the mean constant rate of nucleotide substitutions/site (Ksubs/site) indicated that in nature the variants tend to keep their heterogeneity unchanged from one epidemic episode to the other, even if the outbreaks occur in places very far from each other. This seems to be in agreement with the proposed maintenance of a functional molecular structure as a constraint to CMV satRNA evolution.

  • role of cucumber mosaic virus and its Satellite RNA in the etiology of tomato fruit necrosis in italy
    Archives of Virology, 1993
    Co-Authors: A Crescenzi, L Barbarossa, Fabrizio Cillo, A Di Franco, N Vovlas, D Gallitelli
    Abstract:

    A cucumber mosaic virus (CMV) isolate supporting a natural 390-ribonucleotide Satellite was used to reproduce under experimental conditions a disease of processing tomatoes called fruit necrosis. The virus induced incomplete differentiation of the vascular tissue of fruit stalks, which was the likely cause of the disease. On the other hand, the Satellite RNA attenuated viral symptoms on tomato leaves reproducing the disease pattern typically observed in the field. The biological properties of this seemingly new variant of cucumoviral Satellite RNAs were determined.