Plant Viral Vectors
Plant Viral Vectors for Protein Expression
from Yuri Y. Gleba and Anatoli Giritch writing in Recent Advances in Plant Virology
Plant-virus-driven transient expression of heterologous proteins is the basis of several mature manufacturing processes that are currently being used for the production of multiple proteins including vaccine antigens and antibodies. Viral vectors have also become useful tools for research. In recent years, advances have been made both in the development of first-generation vectors (those that employ the 'full virus' strategy) as well as second-generation vectors designed using the 'deconstructed virus' approach. This second strategy relies on Agrobacterium as a vector to deliver DNA copies of one or more viral RNA replicons. Among the most often used viral backbones are those of Tobacco mosaic virus, Potato virus X, and Cowpea mosaic virus. Prototypes of industrial processes that provide for high-yield, rapid scale-up, and fast manufacturing have been recently developed using viral vectors, with several manufacturing facilities compliant with good manufacturing practices (GMP) in place, and a number of pharmaceutical proteins currently in pre-clinical and clinical trials.
Further reading: Recent Advances in Plant Virology | Virology Publications
from Yuri Y. Gleba and Anatoli Giritch writing in Recent Advances in Plant Virology
Plant-virus-driven transient expression of heterologous proteins is the basis of several mature manufacturing processes that are currently being used for the production of multiple proteins including vaccine antigens and antibodies. Viral vectors have also become useful tools for research. In recent years, advances have been made both in the development of first-generation vectors (those that employ the 'full virus' strategy) as well as second-generation vectors designed using the 'deconstructed virus' approach. This second strategy relies on Agrobacterium as a vector to deliver DNA copies of one or more viral RNA replicons. Among the most often used viral backbones are those of Tobacco mosaic virus, Potato virus X, and Cowpea mosaic virus. Prototypes of industrial processes that provide for high-yield, rapid scale-up, and fast manufacturing have been recently developed using viral vectors, with several manufacturing facilities compliant with good manufacturing practices (GMP) in place, and a number of pharmaceutical proteins currently in pre-clinical and clinical trials.
Further reading: Recent Advances in Plant Virology | Virology Publications
Viral Species Diversity of Plants
Genomic Approaches to Discovery of Viral Species Diversity of Non-cultivated Plants
from Ulrich Melcher and Veenita Grover writing in Recent Advances in Plant Virology
Outbreaks of newly emerging and re-emerging animal and plant viruses pose a constant threat to public health and food security and emphasize the need to develop efficient methods for viral detection and identification. Ongoing studies for discovery of viral species in non-cultivated plants utilize genomic approaches for systematic unbiased searches for viruses related to known viruses. Genomic approaches use various combinations of methods for sampling the environment, enriching samples for content of viral genomes, amplifying nucleic acids, and detecting virus-related sequences among the amplified nucleic acids. These methods include particularly array hybridization to macroarrays and microarrays, and various megasequencing approaches. In all cases, relatives of known viruses are discovered. However, the identification of a novel plant virus completely unrelated to known ones remains a challenge. Despite a growing list of viruses infecting wild plants, virus infections in wild plant communities are often underestimated relative to cultivated systems, since viruses in wild plants are generally considered not to harm the host. Viruses may not be explicitly damaging wild plants, but their biodiversity and abundance suggest an important role of these viruses in ecosystems. These roles should not be under-rated just because they are under-researched.
Further reading: Recent Advances in Plant Virology | Virology Publications
from Ulrich Melcher and Veenita Grover writing in Recent Advances in Plant Virology
Outbreaks of newly emerging and re-emerging animal and plant viruses pose a constant threat to public health and food security and emphasize the need to develop efficient methods for viral detection and identification. Ongoing studies for discovery of viral species in non-cultivated plants utilize genomic approaches for systematic unbiased searches for viruses related to known viruses. Genomic approaches use various combinations of methods for sampling the environment, enriching samples for content of viral genomes, amplifying nucleic acids, and detecting virus-related sequences among the amplified nucleic acids. These methods include particularly array hybridization to macroarrays and microarrays, and various megasequencing approaches. In all cases, relatives of known viruses are discovered. However, the identification of a novel plant virus completely unrelated to known ones remains a challenge. Despite a growing list of viruses infecting wild plants, virus infections in wild plant communities are often underestimated relative to cultivated systems, since viruses in wild plants are generally considered not to harm the host. Viruses may not be explicitly damaging wild plants, but their biodiversity and abundance suggest an important role of these viruses in ecosystems. These roles should not be under-rated just because they are under-researched.
Further reading: Recent Advances in Plant Virology | Virology Publications
Emergence of Plant RNA Viruses
Evolutionary Constraints on Emergence of Plant RNA Viruses
from Santiago F. Elena writing in Recent Advances in Plant Virology
Over the recent years, agricultural activity in many regions has been compromised by a succession of devastating epidemics caused by new viruses that switched host species, or by new variants of classic viruses that acquired new virulence factors or changed their epidemiological patterns. Although viral emergence has been classically associated with ecological change or with agronomical practices that brought in contact reservoirs and crop species, it has become obvious that the picture is much more complex, and results from an evolutionary process in which the main players are the changes in ecological factors, the tremendous genetic plasticity of viruses, the several host factors required for virus replication, and a strong stochastic component. A recent review puts the emergence of RNA viruses into the framework of evolutionary genetics and reviews the basic notions necessary to understand emergence, stressing that viral emergence begins with a stochastic process that involves the transmission of a pre-existing viral strain with the right genetic background into a new host species, followed by adaptation to the new host during the early stages of infection.
Further reading: Recent Advances in Plant Virology | Virology Publications
from Santiago F. Elena writing in Recent Advances in Plant Virology
Over the recent years, agricultural activity in many regions has been compromised by a succession of devastating epidemics caused by new viruses that switched host species, or by new variants of classic viruses that acquired new virulence factors or changed their epidemiological patterns. Although viral emergence has been classically associated with ecological change or with agronomical practices that brought in contact reservoirs and crop species, it has become obvious that the picture is much more complex, and results from an evolutionary process in which the main players are the changes in ecological factors, the tremendous genetic plasticity of viruses, the several host factors required for virus replication, and a strong stochastic component. A recent review puts the emergence of RNA viruses into the framework of evolutionary genetics and reviews the basic notions necessary to understand emergence, stressing that viral emergence begins with a stochastic process that involves the transmission of a pre-existing viral strain with the right genetic background into a new host species, followed by adaptation to the new host during the early stages of infection.
Further reading: Recent Advances in Plant Virology | Virology Publications
Plant Infection by Viruses
Population Dynamics and Genetics of Plant Infection by Viruses
from Fernando García-Arenal and Aurora Fraile writing in Recent Advances in Plant Virology
During the last thirty years, progress in understanding the mechanistic aspects of virus-plant interactions has been remarkable, notably in aspects such as genome replication, movement within the infected host or pathogenesis and resistance. Progress in understanding the population dynamics and genetics of plant infection by viruses has not been as great. However, understanding the kinetics of plant colonisation and the genetic structure of the within-host virus population is necessary for addressing many issues of plant-virus interaction and of virus evolution. The quantitative aspects of plant infection and colonisation by viruses were mostly addressed during the early period of plant virology, when many detailed studies were published that often incorporated mathematical modelling. These issues have not been thoroughly re-examined using molecular techniques. Recent work has focussed on the description of the genetic structure of the virus population at the organ and the plant level. Data suggest that in spite of huge fecundity, the effective numbers of the within-host virus population may be small due to severe population bottlenecks at each stage of plant infection and colonisation, which results in a spatially structured population.
Further reading: Recent Advances in Plant Virology | Virology Publications
from Fernando García-Arenal and Aurora Fraile writing in Recent Advances in Plant Virology
During the last thirty years, progress in understanding the mechanistic aspects of virus-plant interactions has been remarkable, notably in aspects such as genome replication, movement within the infected host or pathogenesis and resistance. Progress in understanding the population dynamics and genetics of plant infection by viruses has not been as great. However, understanding the kinetics of plant colonisation and the genetic structure of the within-host virus population is necessary for addressing many issues of plant-virus interaction and of virus evolution. The quantitative aspects of plant infection and colonisation by viruses were mostly addressed during the early period of plant virology, when many detailed studies were published that often incorporated mathematical modelling. These issues have not been thoroughly re-examined using molecular techniques. Recent work has focussed on the description of the genetic structure of the virus population at the organ and the plant level. Data suggest that in spite of huge fecundity, the effective numbers of the within-host virus population may be small due to severe population bottlenecks at each stage of plant infection and colonisation, which results in a spatially structured population.
Further reading: Recent Advances in Plant Virology | Virology Publications
Control Measures Against Viruses
Integrated Control Measures Against Viruses and Their Vectors
from Alberto Fereres and Aranzazu Moreno writing in Recent Advances in Plant Virology
Viruses and their vectors produce severe damage to crops worldwide. Of importance are the strategies and tactics used to manage vectors of plant viruses, with special attention to insects, by far the most important type of vector. The philosophy and principles of Integrated Pest Management (IPM) developed long ago can still provide an effective and sustainable way to manage insect vectors of virus diseases of plants. Preventive strategies such as the development of models that forecast virus disease outbreaks together with host plant resistance, cultural and physical tactics are the most effective ways to control nonpersistently-transmitted viruses. A reduction in vector numbers using conventional systemic insecticides or innundative biological control agents can also provide effective control of persistently-transmitted viruses. Recent advances on understanding of the mode of transmission of plant viruses are also a very promising way to develop molecules to block putative virus binding sites within the vector and to avoid virus retention and transmission. Also, the characterization of aphid's salivary components that is underway may facilitate the development of new tools to interfere with the process of transmission of plant viruses.
Further reading: Recent Advances in Plant Virology | Virology Publications
from Alberto Fereres and Aranzazu Moreno writing in Recent Advances in Plant Virology
Viruses and their vectors produce severe damage to crops worldwide. Of importance are the strategies and tactics used to manage vectors of plant viruses, with special attention to insects, by far the most important type of vector. The philosophy and principles of Integrated Pest Management (IPM) developed long ago can still provide an effective and sustainable way to manage insect vectors of virus diseases of plants. Preventive strategies such as the development of models that forecast virus disease outbreaks together with host plant resistance, cultural and physical tactics are the most effective ways to control nonpersistently-transmitted viruses. A reduction in vector numbers using conventional systemic insecticides or innundative biological control agents can also provide effective control of persistently-transmitted viruses. Recent advances on understanding of the mode of transmission of plant viruses are also a very promising way to develop molecules to block putative virus binding sites within the vector and to avoid virus retention and transmission. Also, the characterization of aphid's salivary components that is underway may facilitate the development of new tools to interfere with the process of transmission of plant viruses.
Further reading: Recent Advances in Plant Virology | Virology Publications
Resistance to Viruses in Plants
Sustainable Management of Plant Resistance to Viruses
from Benoît Moury, Alberto Fereres, Fernando García-Arenal and Hervé Lecoq writing in Recent Advances in Plant Virology
Although viruses are among the parasites which induce the most severe damages on cultivated plants, few control methods have been developed against them. Notably, no curative methods can be applied against virus diseases in crops. In view of this major economic problem, the development of resistant cultivars has become a critical factor of competitiveness for breeders. However, plant - virus interactions are highly dynamic and the selective pressure exerted by plant resistance frequently favours the emergence of adapted virus populations. Given the scarcity of resistance genes, there is consequently an urgent need to increase the sustainability of these genetic resources. A recent publication reviews the biological mechanisms which allow the emergence of virus populations adapted to plant resistances and how we can use this knowledge to explain the relative durability of different resistance genes, to built predictors of resistance durability and to combine the use of resistances with other control methods to increase their sustainability.
Further reading: Recent Advances in Plant Virology | Virology Publications
from Benoît Moury, Alberto Fereres, Fernando García-Arenal and Hervé Lecoq writing in Recent Advances in Plant Virology
Although viruses are among the parasites which induce the most severe damages on cultivated plants, few control methods have been developed against them. Notably, no curative methods can be applied against virus diseases in crops. In view of this major economic problem, the development of resistant cultivars has become a critical factor of competitiveness for breeders. However, plant - virus interactions are highly dynamic and the selective pressure exerted by plant resistance frequently favours the emergence of adapted virus populations. Given the scarcity of resistance genes, there is consequently an urgent need to increase the sustainability of these genetic resources. A recent publication reviews the biological mechanisms which allow the emergence of virus populations adapted to plant resistances and how we can use this knowledge to explain the relative durability of different resistance genes, to built predictors of resistance durability and to combine the use of resistances with other control methods to increase their sustainability.
Further reading: Recent Advances in Plant Virology | Virology Publications
Virus Resistance in Plants
Advanced Breeding for Virus Resistance in Plants
from Alain Palloix and Frank Ordon writing in Recent Advances in Plant Virology
Breeding for virus resistance was successful in the past years using conventional breeding methods since many virus resistant cultivars have been delivered for a wide range of crops. Genome mapping provided molecular markers for many resistance loci (i.e., major genes or Quantitative Trait Loci) that were introgressed into cultivars e.g., through backcross breeding schemes. Molecular mapping also delivered much information on the genomic architecture of polygenic and quantitative resistances. However, marker assisted selection for such complex traits is difficult so that the combination of quantitative resistance factors from multiallelic origins commonly relies on sophisticated phenotyping procedures. The cloning of resistance genes and the rapid development of high throughput molecular technologies increased the access to functional markers and multiallelic markers, promoting the applicability of marker assisted selection for complex traits at the whole genome scale in the near future. In parallel, the advances in the identification of molecular determinants of plant/virus interactions and in genetics and evolution of virus populations provide new selection criteria for breeders to choose the most durable resistance genes and gene combinations, so that breeding for durable virus resistance becomes an accessible quest.
Further reading: Recent Advances in Plant Virology | Virology Publications
from Alain Palloix and Frank Ordon writing in Recent Advances in Plant Virology
Breeding for virus resistance was successful in the past years using conventional breeding methods since many virus resistant cultivars have been delivered for a wide range of crops. Genome mapping provided molecular markers for many resistance loci (i.e., major genes or Quantitative Trait Loci) that were introgressed into cultivars e.g., through backcross breeding schemes. Molecular mapping also delivered much information on the genomic architecture of polygenic and quantitative resistances. However, marker assisted selection for such complex traits is difficult so that the combination of quantitative resistance factors from multiallelic origins commonly relies on sophisticated phenotyping procedures. The cloning of resistance genes and the rapid development of high throughput molecular technologies increased the access to functional markers and multiallelic markers, promoting the applicability of marker assisted selection for complex traits at the whole genome scale in the near future. In parallel, the advances in the identification of molecular determinants of plant/virus interactions and in genetics and evolution of virus populations provide new selection criteria for breeders to choose the most durable resistance genes and gene combinations, so that breeding for durable virus resistance becomes an accessible quest.
Further reading: Recent Advances in Plant Virology | Virology Publications
Plant Resistance to Viruses
Plant Resistance to Viruses Mediated by Translation Initiation Factors
from Olivier Le Gall, Miguel A. Aranda and Carole Caranta writing in Recent Advances in Plant Virology
Host resistance to viruses can show dominant or recessive inheritance. Remarkably, recessive resistance genes are much more common for viruses than for other plant pathogens. Recessive resistances to viruses are especially well documented within the dicotyledons, and have been described for various viruses that belong to very different viral genera, although clearly they predominate among viruses belonging to the genus Potyvirus. The elucidation of the molecular nature of this particular class of resistance genes is recent, but has so far only revealed a group of proteins linked to the translation machinery, chiefly the eukaryotic translation initiation factors (eIF) 4E and 4G. There are specific features and mechanisms of eIF4E- and 4G-mediated resistances to potyviruses and viruses belonging to other genera, such as carmoviruses.
Further reading: Recent Advances in Plant Virology | Virology Publications
from Olivier Le Gall, Miguel A. Aranda and Carole Caranta writing in Recent Advances in Plant Virology
Host resistance to viruses can show dominant or recessive inheritance. Remarkably, recessive resistance genes are much more common for viruses than for other plant pathogens. Recessive resistances to viruses are especially well documented within the dicotyledons, and have been described for various viruses that belong to very different viral genera, although clearly they predominate among viruses belonging to the genus Potyvirus. The elucidation of the molecular nature of this particular class of resistance genes is recent, but has so far only revealed a group of proteins linked to the translation machinery, chiefly the eukaryotic translation initiation factors (eIF) 4E and 4G. There are specific features and mechanisms of eIF4E- and 4G-mediated resistances to potyviruses and viruses belonging to other genera, such as carmoviruses.
Further reading: Recent Advances in Plant Virology | Virology Publications
NB-LRR Immune Receptors in Plant Virus Defense
NB-LRR Immune Receptors in Plant Virus Defense
from Patrick Cournoyer and Savithramma P. Dinesh-Kumar writing in Recent Advances in Plant Virology
Resistance genes protect plants from infection by viruses and many other classes of pathogens. The dominant, anti-viral R genes that have been cloned thus far encode NB-LRR immune receptors that detect a single viral protein and trigger defense. Many different types of viral proteins are known to elicit defense by corresponding NB-LRRs. Defense often results in a type of localized programmed cell death at the site of attempted pathogen infection known as the hypersensitive response (HR-PCD), but some NB-LRRs confer resistance to viruses without HR-PCD. The activation of NB-LRRs triggers manifold signaling events including reactive oxygen species (ROS) production, nitric oxide (NO) production, calcium (Ca2+) influx, activation of mitogen activated protein kinases (MAPKs), and production of the plant hormones salicylic acid (SA), jasmonic acid (JA), and ethylene. After a successful NB-LRR-mediated defense event, the plant exhibits heightened resistance to future pathogen challenge in a state called systemic acquired resistance.
Further reading: Recent Advances in Plant Virology | Virology Publications
from Patrick Cournoyer and Savithramma P. Dinesh-Kumar writing in Recent Advances in Plant Virology
Resistance genes protect plants from infection by viruses and many other classes of pathogens. The dominant, anti-viral R genes that have been cloned thus far encode NB-LRR immune receptors that detect a single viral protein and trigger defense. Many different types of viral proteins are known to elicit defense by corresponding NB-LRRs. Defense often results in a type of localized programmed cell death at the site of attempted pathogen infection known as the hypersensitive response (HR-PCD), but some NB-LRRs confer resistance to viruses without HR-PCD. The activation of NB-LRRs triggers manifold signaling events including reactive oxygen species (ROS) production, nitric oxide (NO) production, calcium (Ca2+) influx, activation of mitogen activated protein kinases (MAPKs), and production of the plant hormones salicylic acid (SA), jasmonic acid (JA), and ethylene. After a successful NB-LRR-mediated defense event, the plant exhibits heightened resistance to future pathogen challenge in a state called systemic acquired resistance.
Further reading: Recent Advances in Plant Virology | Virology Publications
Plant Virology
Carole Caranta, Miguel A. Aranda, Mark Tepfer and J.J. Lopez-Moya (INRA-UR , Génétique et Amélioration des Fruits et Légumes, Montfavet cedex, France;Centro de Edafología y Biología Aplicada del Segura (CEBAS), CSIC, Espinardo, Murcia, Spain;Laboratoire de Biologie Cellulaire, INRA, F Versailles Cedex, France;IBMB, Centre for Research in Agricultural Genomics (CRAG) CSIC-IRTA-UAB, Barcelona, Spain, respectively) present a new book on Recent Advances in Plant Virology
Viruses that infect plants are responsible for reduction in both yield and quality of crops around the world, and are thus of great economic importance. This has provided the impetus for the extensive research into the molecular and cellular biology of these pathogens and into their interaction with their plant hosts and their vectors. However interest in plant viruses extends beyond their ability to damage crops. Many plant viruses, for example tobacco mosaic virus, have been used as model systems to provide basic understanding of how viruses express genes and replicate. Others permitted the elucidation of the processes underlying RNA silencing, now recognised as a core epigenetic mechanism underpinning numerous areas of biology.
This book attests to the huge diversity of research in plant molecular virology. Written by world authorities in the field, the book opens with two chapters on the translation and replication of viral RNA. Following chapters cover topics such as viral movement within and between plants, plant responses to viral infection, antiviral control measures, virus evolution, and newly emerging plant viruses. To close there are two chapters on biotechnological applications of plant viruses. Throughout the book the focus is on the most recent, cutting-edge research, making this book essential reading for everyone, from researchers and scholars to students, working with plant viruses.
Viruses that infect plants are responsible for reduction in both yield and quality of crops around the world, and are thus of great economic importance. This has provided the impetus for the extensive research into the molecular and cellular biology of these pathogens and into their interaction with their plant hosts and their vectors. However interest in plant viruses extends beyond their ability to damage crops. Many plant viruses, for example tobacco mosaic virus, have been used as model systems to provide basic understanding of how viruses express genes and replicate. Others permitted the elucidation of the processes underlying RNA silencing, now recognised as a core epigenetic mechanism underpinning numerous areas of biology.
This book attests to the huge diversity of research in plant molecular virology. Written by world authorities in the field, the book opens with two chapters on the translation and replication of viral RNA. Following chapters cover topics such as viral movement within and between plants, plant responses to viral infection, antiviral control measures, virus evolution, and newly emerging plant viruses. To close there are two chapters on biotechnological applications of plant viruses. Throughout the book the focus is on the most recent, cutting-edge research, making this book essential reading for everyone, from researchers and scholars to students, working with plant viruses.
 | Edited by: Carole Caranta, Miguel A. Aranda, Mark Tepfer and J.J. Lopez-Moya ISBN: 978-1-904455-75-2 Publisher: Caister Academic Press Publication Date: February 2011 Cover: hardback |