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Post by ravendra on Nov 18, 2015 4:34:19 GMT -6
Potexviruses have single stranded positive sense RNA genomes. Genomic RNA is capped at 5’ end and has a 3’ poly(A) tail. Potato virus X is the type species of the potexvirus genus. The first complete genome sequence of Potato virus X was determined in 1988. In the same year, the first transgenic plants resistant against PVX infection were developed. In the year 1990, infectious transcripts of PVX from the cDNA were developed. In 1992, PVX was developed as a vector for gene expression. PVX represents the critical evolutionary model for the Potexvirus genus. The viruses of potexvirus genus have a wide host range including potato, brassica and several other dicots. There are a number of genome sequences reported to NCBI that belong to potexvirus genus. These sequences are important for providing information on the genetic diversity of the virus species in the potexvirus genus. The development of cDNA infectious clone was an important step to study the host range and symptomatology of the potexviruses. The availability of an infectious cDNA clone enables us to use the reverse genetics approach to investigate the host range and indentify the genes responsible for disease development. The availability of complete genome sequences of the number of agriculturally important members of potexvirus genus and their infectious cDNA clones as well as the genome sequence information of major hosts like Solanum tuberosum, and Solanum lycopersicum will enable us to screen for the disease resistant genes in the host species using reverse genetics. This will help us to develop strategies to control the potexvirus diseases in the important agricultural crops.
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Post by jontrip247 on Nov 18, 2015 9:10:06 GMT -6
Ravendra,
Please forgive me, but what model(s) are you proposing for the evolution of Potexvirus?
Can the triple gene block (TGB) give insight into the evolution of this virus?
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Post by omararias on Nov 18, 2015 16:40:57 GMT -6
Potexviruses have single stranded positive sense RNA genomes. Genomic RNA is capped at 5’ end and has a 3’ poly(A) tail. Potato virus X is the type species of the potexvirus genus. The first complete genome sequence of Potato virus X was determined in 1988. In the same year, the first transgenic plants resistant against PVX infection were developed. In the year 1990, infectious transcripts of PVX from the cDNA were developed. In 1992, PVX was developed as a vector for gene expression. PVX represents the critical evolutionary model for the Potexvirus genus. The viruses of potexvirus genus have a wide host range including potato, brassica and several other dicots. There are a number of genome sequences reported to NCBI that belong to potexvirus genus. These sequences are important for providing information on the genetic diversity of the virus species in the potexvirus genus. The development of cDNA infectious clone was an important step to study the host range and symptomatology of the potexviruses. The availability of an infectious cDNA clone enables us to use the reverse genetics approach to investigate the host range and indentify the genes responsible for disease development. The availability of complete genome sequences of the number of agriculturally important members of potexvirus genus and their infectious cDNA clones as well as the genome sequence information of major hosts like Solanum tuberosum, and Solanum lycopersicum will enable us to screen for the disease resistant genes in the host species using reverse genetics. This will help us to develop strategies to control the potexvirus diseases in the important agricultural crops. Hi, please could you help me with some questions. I agree with Jon, please could you be more specific about the evolution model that you are writing about? Besides, from what you are relating, which specifically will be the strategy that you would apply for coping the disease? Second, which pathway do you think these type of viruses developed for evolution? Was it co-evolution with host or infection of multiple host species? Thanks. |
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Post by dulanjani on Nov 18, 2015 20:08:04 GMT -6
Potexviruses have single stranded positive sense RNA genomes. Genomic RNA is capped at 5’ end and has a 3’ poly(A) tail. Potato virus X is the type species of the potexvirus genus. The first complete genome sequence of Potato virus X was determined in 1988. In the same year, the first transgenic plants resistant against PVX infection were developed. In the year 1990, infectious transcripts of PVX from the cDNA were developed. In 1992, PVX was developed as a vector for gene expression. PVX represents the critical evolutionary model for the Potexvirus genus. The viruses of potexvirus genus have a wide host range including potato, brassica and several other dicots. There are a number of genome sequences reported to NCBI that belong to potexvirus genus. These sequences are important for providing information on the genetic diversity of the virus species in the potexvirus genus. The development of cDNA infectious clone was an important step to study the host range and symptomatology of the potexviruses. The availability of an infectious cDNA clone enables us to use the reverse genetics approach to investigate the host range and indentify the genes responsible for disease development. The availability of complete genome sequences of the number of agriculturally important members of potexvirus genus and their infectious cDNA clones as well as the genome sequence information of major hosts like Solanum tuberosum, and Solanum lycopersicum will enable us to screen for the disease resistant genes in the host species using reverse genetics. This will help us to develop strategies to control the potexvirus diseases in the important agricultural crops. As you mentioned above in 1988 first transgenic plant resistant to PVX was developed. In one paper i have read that resistance to potato virus X (PVX) is determined by the product of a host resistance gene and a viral determinant specifying either virulence (resistance-breaking ability) or avirulence (resistance sensitivity). The viral coat protein is the determinant of resistance mediated by the host Nx gene while the 25 kDa movement protein is the determinant of Nb-mediated resistance. They were able to recognize different strains that are either virulent or avirulent. There could be two alternative evolutionary mechanisms by which the various strain groups might have evolved: either by recombination between strains carrying virulence (or avirulence) determinants that evolved once only, or alternatively, by independent evolution of at least one virulence (or avirulence) determinant in distinct phylogenetic branches. Which one do you think possibly could occur? and why? |
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Post by ravendra on Nov 20, 2015 6:36:18 GMT -6
Yes, TGB model gives insights into evolution of these viruses. TGB3 is expressed by leaky scanning of the TGB2 subgenomic mRNA. Replication occurs in viral factories recruited by TGB1. The triple gene block proteins allow cell-to-cell and long-distance movement.
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Post by ravendra on Nov 21, 2015 8:06:51 GMT -6
Potexviruses have single stranded positive sense RNA genomes. Genomic RNA is capped at 5’ end and has a 3’ poly(A) tail. Potato virus X is the type species of the potexvirus genus. The first complete genome sequence of Potato virus X was determined in 1988. In the same year, the first transgenic plants resistant against PVX infection were developed. In the year 1990, infectious transcripts of PVX from the cDNA were developed. In 1992, PVX was developed as a vector for gene expression. PVX represents the critical evolutionary model for the Potexvirus genus. The viruses of potexvirus genus have a wide host range including potato, brassica and several other dicots. There are a number of genome sequences reported to NCBI that belong to potexvirus genus. These sequences are important for providing information on the genetic diversity of the virus species in the potexvirus genus. The development of cDNA infectious clone was an important step to study the host range and symptomatology of the potexviruses. The availability of an infectious cDNA clone enables us to use the reverse genetics approach to investigate the host range and indentify the genes responsible for disease development. The availability of complete genome sequences of the number of agriculturally important members of potexvirus genus and their infectious cDNA clones as well as the genome sequence information of major hosts like Solanum tuberosum, and Solanum lycopersicum will enable us to screen for the disease resistant genes in the host species using reverse genetics. This will help us to develop strategies to control the potexvirus diseases in the important agricultural crops. As you mentioned above in 1988 first transgenic plant resistant to PVX was developed. In one paper i have read that resistance to potato virus X (PVX) is determined by the product of a host resistance gene and a viral determinant specifying either virulence (resistance-breaking ability) or avirulence (resistance sensitivity). The viral coat protein is the determinant of resistance mediated by the host Nx gene while the 25 kDa movement protein is the determinant of Nb-mediated resistance. They were able to recognize different strains that are either virulent or avirulent. There could be two alternative evolutionary mechanisms by which the various strain groups might have evolved: either by recombination between strains carrying virulence (or avirulence) determinants that evolved once only, or alternatively, by independent evolution of at least one virulence (or avirulence) determinant in distinct phylogenetic branches. Which one do you think possibly could occur? and why? As you know that strains are defined mainly by two characteristics- 1. Percent sequence similarity between genomes and, 2. symptomatology (they produce different symptoms in the same host). Resistance to virus movement occurs where some kind of movement of virus through the plant is impeded. The hypersensitive response could be regarded as a kind of resistance to virus movement, because movement is arrested by cell death. Your question is- how the various strains might have evolved? It would be recombination between different isolates or different selective pressures. Also, the mutation(s) in the key domains would also greatly alter the disease characteristics. A single amino acid mutation would render the PVX from virulent to avirulent. As reported by David Baulcombe's group at Cambridge University, a single mutation in GDD motif was expressed as GAD or GED which led to no effect on susceptibility to PVX infection in N. benthamiana plants. But, when GDD motif was mutated to be ADD in the conserved motif, the F1 and F2 progeny plants were highly resistant to PVX infection. So, in case of virus evolution, as we know recombination plays a significant role but, I think the possibility of independent evolution by selection pressure would also be a critical factor as a single amino acid substitution or mutation would be lethal for the virus survival. In my opinion, it would not be easy to say with confidence if one or the other hypothesis is being applied when you say PVX strain evolution. |
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Post by ravendra on Nov 21, 2015 13:13:19 GMT -6
Hi, please could you help me with some questions. I agree with Jon, please could you be more specific about the evolution model that you are writing about? Besides, from what you are relating, which specifically will be the strategy that you would apply for coping the disease? Second, which pathway do you think these type of viruses developed for evolution? Was it co-evolution with host or infection of multiple host species? Thanks. There has been a lot of work done towards the development of resistant potato plants against PVX infection. In some earlier work, in the year 2002, V. Doreste et. al. reported transgenic potato plants expressing PVX coat protein gene developed resistance to the viral infection. In this paper, the gene coding for PVX coat protein was expressed in transgenic potato plants obtained by Agrobacterium tumefaciens transformation. Doreste et. al. analyzed a total of one hundred independent clones for resistance to PVX infection under greenhouse conditions as a preliminary test. From this test, 16 clones with the best resistance outcome were selected for a small-scale field trial. Most of these selected clones demonstrated strong resistance against PVX in the potato field. This work reported that there was correlation between resistance to virus infection and expression of the CP gene of PVX in the analyzed clones in the field setting. (Doreste, V. et. al. Phytoparasitica. 2002, pages 177-185).
In a recent publication by Kyoko et. al. (2013) in journal of Molecular Plant Microbe Interaction, there is a report of a replicase of PVX that acts as the resistance-breaking determinant for JAX1-mediated resistance. This publication describes that the lectin-mediated resistance (LMR) has been suggested to comprise an uncharacterized branch of antiviral plant innate immunity. Therefore, in this paper the work was carried out to unveil the feature of resistance conferred by jacalin-type lectin required for potexvirus resistance 1 (JAX1), a recently isolated LMR gene against potexviruses. The authors analyzed the resistance-breaking variants to find the viral component involved in resistance. They used grafting mediated inoculation which is a high-pressure virus inoculation method to obtain PVX variants that can overcome JAX1-mediated resistance. They sequenced the complete genomes of the variants which revealed that a single amino acid in the methyl transferase domain of the replicase encoded by PVX was responsible for this resistance-breaking property. Reintroduction of the amino-acid substitution to avirulent wild-type PVX was sufficient to overcome the JAX1-mediated resistance. There findings concluded that the viral replicase was involved in JAX1-mediated resistance. The paper describes that the residue that determines the resistance-breaking properties was highly conserved among potexviruses, suggesting a general role of the residue in potexvirus–JAX1 interactions.
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Post by ravendra on Nov 21, 2015 13:32:48 GMT -6
Hi, please could you help me with some questions. I agree with Jon, please could you be more specific about the evolution model that you are writing about? Besides, from what you are relating, which specifically will be the strategy that you would apply for coping the disease? Second, which pathway do you think these type of viruses developed for evolution? Was it co-evolution with host or infection of multiple host species? Thanks. In a Plant Cell publication in 1999, A. Bendahmane et. al. from David Baulcombe's group reported that the hypersensitive response-mediated cell death and PVX infection arrest are two separate disease resistance responses in the plants. The paper discusses that the Rx-mediated resistance against PVX, like that controlled by many disease resistance (R) genes, can be described in terms of an elicitor–receptor model. According to this model, there are separate stages in the process involving pathogen recognition and the plant’s response to the pathogen. In Rx-mediated resistance, the pathogen recognition involves an interaction between Rx which encodes the receptor, and the PVX coat protein which is the elicitor. The Rx-mediated resistance was able to suppress accumulation of PVX. One of the critical features of the Rx-mediated resistance is the rapid arrest of PVX accumulation in the initially infected cell and unlike other disease resistance responses, the Rx-mediated resistance is not associated with a hypersensitive response at the site of inoculation but it is active in protoplasts via mechanisms that either suppress virus replication or promote degradation of the viral RNA. Citation: A. Bendahmane et. al. (1999). The Rx gene from potato controls separate virus resistance and cell death responses. The Plant Cell, Vol. 11, 781–791. |
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Post by gabriela on Nov 22, 2015 21:20:04 GMT -6
Potexviruses have single stranded positive sense RNA genomes. Genomic RNA is capped at 5’ end and has a 3’ poly(A) tail. Potato virus X is the type species of the potexvirus genus. The first complete genome sequence of Potato virus X was determined in 1988. In the same year, the first transgenic plants resistant against PVX infection were developed. In the year 1990, infectious transcripts of PVX from the cDNA were developed. In 1992, PVX was developed as a vector for gene expression. PVX represents the critical evolutionary model for the Potexvirus genus. The viruses of potexvirus genus have a wide host range including potato, brassica and several other dicots. There are a number of genome sequences reported to NCBI that belong to potexvirus genus. These sequences are important for providing information on the genetic diversity of the virus species in the potexvirus genus. The development of cDNA infectious clone was an important step to study the host range and symptomatology of the potexviruses. The availability of an infectious cDNA clone enables us to use the reverse genetics approach to investigate the host range and indentify the genes responsible for disease development. The availability of complete genome sequences of the number of agriculturally important members of potexvirus genus and their infectious cDNA clones as well as the genome sequence information of major hosts like Solanum tuberosum, and Solanum lycopersicum will enable us to screen for the disease resistant genes in the host species using reverse genetics. This will help us to develop strategies to control the potexvirus diseases in the important agricultural crops. |
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Post by gabriela on Nov 22, 2015 21:22:14 GMT -6
Potexviruses have single stranded positive sense RNA genomes. Genomic RNA is capped at 5’ end and has a 3’ poly(A) tail. Potato virus X is the type species of the potexvirus genus. The first complete genome sequence of Potato virus X was determined in 1988. In the same year, the first transgenic plants resistant against PVX infection were developed. In the year 1990, infectious transcripts of PVX from the cDNA were developed. In 1992, PVX was developed as a vector for gene expression. PVX represents the critical evolutionary model for the Potexvirus genus. The viruses of potexvirus genus have a wide host range including potato, brassica and several other dicots. There are a number of genome sequences reported to NCBI that belong to potexvirus genus. These sequences are important for providing information on the genetic diversity of the virus species in the potexvirus genus. The development of cDNA infectious clone was an important step to study the host range and symptomatology of the potexviruses. The availability of an infectious cDNA clone enables us to use the reverse genetics approach to investigate the host range and indentify the genes responsible for disease development. The availability of complete genome sequences of the number of agriculturally important members of potexvirus genus and their infectious cDNA clones as well as the genome sequence information of major hosts like Solanum tuberosum, and Solanum lycopersicum will enable us to screen for the disease resistant genes in the host species using reverse genetics. This will help us to develop strategies to control the potexvirus diseases in the important agricultural crops. thanks so much for the info ravendra, in this group of virus, which is the main evolution model? is it recombination? |
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Post by omararias on Nov 22, 2015 22:26:58 GMT -6
Hi, please could you help me with some questions. I agree with Jon, please could you be more specific about the evolution model that you are writing about? Besides, from what you are relating, which specifically will be the strategy that you would apply for coping the disease? Second, which pathway do you think these type of viruses developed for evolution? Was it co-evolution with host or infection of multiple host species? Thanks. In a Plant Cell publication in 1999, A. Bendahmane et. al. from David Baulcombe's group reported that the hypersensitive response-mediated cell death and PVX infection arrest are two separate disease resistance responses in the plants. The paper discusses that the Rx-mediated resistance against PVX, like that controlled by many disease resistance (R) genes, can be described in terms of an elicitor–receptor model. According to this model, there are separate stages in the process involving pathogen recognition and the plant’s response to the pathogen. In Rx-mediated resistance, the pathogen recognition involves an interaction between Rx which encodes the receptor, and the PVX coat protein which is the elicitor. The Rx-mediated resistance was able to suppress accumulation of PVX. One of the critical features of the Rx-mediated resistance is the rapid arrest of PVX accumulation in the initially infected cell and unlike other disease resistance responses, the Rx-mediated resistance is not associated with a hypersensitive response at the site of inoculation but it is active in protoplasts via mechanisms that either suppress virus replication or promote degradation of the viral RNA. Citation: A. Bendahmane et. al. (1999). The Rx gene from potato controls separate virus resistance and cell death responses. The Plant Cell, Vol. 11, 781–791. Ok thanks for the information this model of resistance (elicitor-receptor) seems very interesting |
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