Gene silencing is the regulation of gene expression in a cell to prevent the expression of a certain gene. Gene silencing can occur during either transcription or translation and is often used in research. In particular, methods used to silence genes are being increasingly used to produce therapeutics to combat cancer and other diseases, such as infectious diseases and neurodegenerative disorders.
Virusoids are circular single-stranded RNA(s) dependent on viruses for replication and encapsidation. The genome of virusoids consists of several hundred (200–400) nucleotides and does not code for any proteins.
Agrobacterium is a genus of Gram-negative bacteria established by H. J. Conn that uses horizontal gene transfer to cause tumors in plants. Agrobacterium tumefaciens is the most commonly studied species in this genus. Agrobacterium is well known for its ability to transfer DNA between itself and plants, and for this reason it has become an important tool for genetic engineering.
Plant viruses are viruses that have the potential to affect plants. Like all other viruses, plant viruses are obligate intracellular parasites that do not have the molecular machinery to replicate without a host. Plant viruses can be pathogenic to vascular plants.
A tumour inducing (Ti) plasmid is a plasmid found in pathogenic species of Agrobacterium, including A. tumefaciens, A. rhizogenes, A. rubi and A. vitis.
Tomato bushy stunt virus (TBSV) is a virus of the tombusvirus family. It was first reported in tomatoes in 1935 and primarily affects vegetable crops, though it is not generally considered an economically significant plant pathogen. Depending upon the host, TBSV causes stunting of growth, leaf mottling, and deformed or absent fruit. The virus is likely to be soil-borne in the natural setting, but can also be transmitted mechanically, for example through contaminated cutting tools. TBSV has been used as a model system in virology research on the life cycle of plant viruses, particularly in experimental infections of the model host plant Nicotiana benthamiana.
Gene delivery is the process of introducing foreign genetic material, such as DNA or RNA, into host cells. Gene delivery must reach the genome of the host cell to induce gene expression. Successful gene delivery requires the foreign gene delivery to remain stable within the host cell and can either integrate into the genome or replicate independently of it. This requires foreign DNA to be synthesized as part of a vector, which is designed to enter the desired host cell and deliver the transgene to that cell's genome. Vectors utilized as the method for gene delivery can be divided into two categories, recombinant viruses and synthetic vectors.
Cocksfoot mottle virus (CfMV) is a pathogenic plant virus belonging to the genus Sobemovirus. The virus appears in southern and central England. It is transmitted by beetles Lema melanopa and Lema lichenis and is common in crops of cocksfoot and cocksfoot/legume mixtures.
Potato mop-top virus (PMTV) is a plant pathogenic virus transmitted through the vector Spongospora subterranea that affects potatoes. PMTV belongs to family of Virgaviridae, and the genus Pomovirus. The virus was first identified in 1966 by Calvert and Harrison in Britain, and is now reported in many other potato cultivating regions of the world including U.S.A., Canada, China, Pakistan, Japan, South American countries and many parts of Europe. Many disease management systems have been found to be ineffective against the virus, although a combination of sanitation and vector controls seems to work well.
Potato virus X (PVX) is a plant pathogenic virus of the family Alphaflexiviridae and the order Tymovirales.
Plant disease resistance protects plants from pathogens in two ways: by pre-formed structures and chemicals, and by infection-induced responses of the immune system. Relative to a susceptible plant, disease resistance is the reduction of pathogen growth on or in the plant, while the term disease tolerance describes plants that exhibit little disease damage despite substantial pathogen levels. Disease outcome is determined by the three-way interaction of the pathogen, the plant, and the environmental conditions.
Genetic engineering techniques allow the modification of animal and plant genomes. Techniques have been devised to insert, delete, and modify DNA at multiple levels, ranging from a specific base pair in a specific gene to entire genes. There are a number of steps that are followed before a genetically modified organism (GMO) is created. Genetic engineers must first choose what gene they wish to insert, modify, or delete. The gene must then be isolated and incorporated, along with other genetic elements, into a suitable vector. This vector is then used to insert the gene into the host genome, creating a transgenic or edited organism.
Soybean vein necrosis orthotospovirus is a plant pathogenic virus of soybeans. SVNV is a relatively new virus, which was discovered in Tennessee in 2008 and has recently been found in many US states from the Southeast and East coast to some western states including CA. This pathogen initially causes intraveinal chlorosis (yellowing) in leaves. This chlorosis then spreads throughout the leaf and eventually these chlorotic areas can become necrotic. It is a member of the order Bunyavirales, family Tospoviridae and genus Orthotospovirus, which is the only genus within this virus family that infects plants. Like other members of Bunyavirales, this virus is enveloped and has a negative sense single-stranded RNA (−ssRNA) genome composed of three genomic segments. It encodes proteins on the M and S segments in an ambisense manner.
RNA silencing suppressor p19 is a protein expressed from the ORF4 gene in the genome of tombusviruses. These viruses are positive-sense single-stranded RNA viruses that infect plant cells, in which RNA silencing forms a widespread and robust antiviral defense system. The p19 protein serves as a counter-defense strategy, specifically binding the 19- to 21-nucleotide double-stranded RNAs that function as small interfering RNA (siRNA) in the RNA silencing system. By sequestering siRNA, p19 suppresses RNA silencing and promotes viral proliferation. The p19 protein is considered a significant virulence factor and a component of an evolutionary arms race between plants and their pathogens.
Transient expression, more frequently referred to "transient gene expression", is the temporary expression of genes that are expressed for a short time after nucleic acid, most frequently plasmid DNA encoding an expression cassette, has been introduced into eukaryotic cells with a chemical delivery agent like calcium phosphate (CaPi) or polyethyleneimine (PEI). However, unlike "stable expression," the foreign DNA does not fuse with the host cell DNA, resulting in the inevitable loss of the vector after several cell replication cycles. The majority of transient gene expressions are done with cultivated animal cells. The technique is also used in plant cells; however, the transfer of nucleic acids into these cells requires different methods than those with animal cells. In both plants and animals, transient expression should result in a time-limited use of transferred nucleic acids, since any long-term expression would be called "stable expression."
Tomato spotted wilt orthotospovirus (TSWV) is a spherical negative-sense RNA virus. Transmitted by thrips, it causes serious losses in economically important crops and it is one of the most economically devastating plant viruses in the world.
RNA-directed DNA methylation (RdDM) is a biological process in which non-coding RNA molecules direct the addition of DNA methylation to specific DNA sequences. The RdDM pathway is unique to plants, although other mechanisms of RNA-directed chromatin modification have also been described in fungi and animals. To date, the RdDM pathway is best characterized within angiosperms, and particularly within the model plant Arabidopsis thaliana. However, conserved RdDM pathway components and associated small RNAs (sRNAs) have also been found in other groups of plants, such as gymnosperms and ferns. The RdDM pathway closely resembles other sRNA pathways, particularly the highly conserved RNAi pathway found in fungi, plants, and animals. Both the RdDM and RNAi pathways produce sRNAs and involve conserved Argonaute, Dicer and RNA-dependent RNA polymerase proteins.
Pal Maliga is a plant molecular biologist. He is Distinguished Professor of Plant Biology and Laboratory Director at the Waksman Institute of Microbiology, Rutgers University. He is known for developing the technology of chloroplast genome engineering in land plants and its applications in basic science and biotechnology.
Michael Maurice Goodin was a Jamaican-born plant virologist. He researched interactions between the virus and the host cell, focusing on rhabdoviruses that infect plants. He also studied emerging plant viruses, including economically significant viruses infecting coffee plants. He co-invented a widely used method of generating large amounts of expressed proteins in leaves infiltrated with Agrobacterium, and developed other techniques for plant molecular virology research. Goodin moved to the United States in around 1989 and was a professor at the University of Kentucky from 2017 until his death.
The tomato chlorosis virus (ToCV) is an RNA virus belonging to the genus crinivirus, a group of plant-infecting viruses in the family Closteroviridae.
