Use in plant propagation
Hairy root culture can also be used for regeneration of whole plants and for production of artificial seeds. [7]
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Hairy root culture, also called transformed root culture, is a type of plant tissue culture that is used to study plant metabolic processes or to produce valuable secondary metabolites or recombinant proteins, often with plant genetic engineering. [1]
A naturally occurring soil bacterium Agrobacterium rhizogenes that contains root-inducing plasmids (also called Ri plasmids) can infect plant roots and cause them to produce a food source for the bacterium, opines, and to grow abnormally. [2] The abnormal roots are particularly easy to culture in artificial media because hormones are not needed in contrast to adventitious roots, [2] and they are neoplastic, with indefinite growth. The neoplastic roots produced by A. rhizogenes infection have a high growth rate (compared to untransformed adventitious roots), as well as genetic and biochemical stability.
Currently the main constraint for commercial utilization of hairy root culture is the development and up-scaling of appropriate (bioreactors) vessels for the delicate and sensitive hairy roots. [2] [3] [4]
Some of the applied research on utilization of hairy root cultures has been and is conducted at VTT Technical Research Centre of Finland Ltd. [5] [6] Other labs working on hairy roots are the phytotechnology lab of Amiens University and the Arkansas Biosciences Institute.
Hairy root cultures can be used for phytoremediation, and are particularly valuable for studies of the metabolic processes involved in phytoremediation. [2]
Further applications include detailed studies of fundamental molecular, genetic and biochemical aspects of genetic transformation and of hairy root induction. [7]
The Ri plasmids can be engineered to also contain T-DNA, used for genetic transformation (biotransformation) of the plant cells. The resulting genetically transformed root cultures can produce high levels of secondary metabolites, comparable or even higher than those of intact plants. [8]
Hairy root culture can also be used for regeneration of whole plants and for production of artificial seeds. [7]
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Bacterial conjugation is the transfer of genetic material between bacterial cells by direct cell-to-cell contact or by a bridge-like connection between two cells. This takes place through a pilus. It is a parasexual mode of reproduction in bacteria.
In molecular biology and genetics, transformation is the genetic alteration of a cell resulting from the direct uptake and incorporation of exogenous genetic material from its surroundings through the cell membrane(s). For transformation to take place, the recipient bacterium must be in a state of competence, which might occur in nature as a time-limited response to environmental conditions such as starvation and cell density, and may also be induced in a laboratory.
Agrobacterium radiobacter is the causal agent of crown gall disease in over 140 species of eudicots. It is a rod-shaped, Gram-negative soil bacterium. Symptoms are caused by the insertion of a small segment of DNA, from a plasmid into the plant cell, which is incorporated at a semi-random location into the plant genome. Plant genomes can be engineered by use of Agrobacterium for the delivery of sequences hosted in T-DNA binary vectors.
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.
The transfer DNA is the transferred DNA of the tumor-inducing (Ti) plasmid of some species of bacteria such as Agrobacterium tumefaciens and Agrobacterium rhizogenes . The T-DNA is transferred from bacterium into the host plant's nuclear DNA genome. The capability of this specialized tumor-inducing (Ti) plasmid is attributed to two essential regions required for DNA transfer to the host cell. The T-DNA is bordered by 25-base-pair repeats on each end. Transfer is initiated at the right border and terminated at the left border and requires the vir genes of the Ti plasmid.
Mary-Dell Chilton is one of the founders of modern plant biotechnology.
A tumour inducing (Ti) plasmid is a plasmid found in pathogenic species of Agrobacterium, including A. tumefaciens, A. rhizogenes, A. rubi and A. vitis.
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Rhizobium rhizogenes is a Gram-negative soil bacterium that produces hairy root disease in dicotyledonous plants. R. rhizogenes induces the formation of proliferative multiple-branched adventitious roots at the site of infection, so-called 'hairy roots'. It also induces galls.
Nicotiana tabacum, or cultivated tobacco, is an annually grown herbaceous plant of the genus Nicotiana. N. tabacum is the most commonly grown species in the genus Nicotiana, as the plant's leaves are commercially harvested to be processed into tobacco for human use. The plant is tropical in origin, is commonly grown throughout the world, and is often found in cultivation. It grows to heights between 1 and 2 meters. Research is ongoing into its ancestry among wild Nicotiana species, but it is believed to be a hybrid of Nicotiana sylvestris, N. tomentosiformis, and possibly N. otophora.
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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.
Agroinfiltration is a method used in plant biology and especially lately in plant biotechnology to induce transient expression of genes in a plant, or isolated leaves from a plant, or even in cultures of plant cells, in order to produce a desired protein. In the method, a suspension of Agrobacterium tumefaciens is introduced into a plant leaf by direct injection or by vacuum infiltration, or brought into association with plant cells immobilised on a porous support, whereafter the bacteria transfer the desired gene into the plant cells via transfer of T-DNA. The main benefit of agroinfiltration when compared to the more traditional plant transformation is speed and convenience, although yields of the recombinant protein are generally also higher and more consistent.
Rhodococcus fascians is a Gram positive bacterial phytopathogen that causes leafy gall disease. R. fascians is the only phytopathogenic member of the genus Rhodococcus; its host range includes both dicotyledonous and monocotyledonous hosts. Because it commonly afflicts tobacco (Nicotiana) plants, it is an agriculturally significant pathogen.
Plant transformation vectors are plasmids that have been specifically designed to facilitate the generation of transgenic plants. The most commonly used plant transformation vectors are termed T-DNA binary vectors and are often replicated in both E. coli, a common lab bacterium, and Agrobacterium tumefaciens, a plant-virulent bacterium used to insert the recombinant (customized) DNA into plants. Plant Transformation vectors contain three key elements;
Plant tissue culture is a collection of techniques used to maintain or grow plant cells, tissues, or organs under sterile conditions on a nutrient culture medium of known composition. It is widely used, to produce clones of a plant in a method known as micropropagation. Different techniques in plant tissue culture may offer certain advantages over traditional methods of propagation, including:
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Acetosyringone is a phenolic natural product and a chemical compound related to acetophenone and 2,6-dimethoxyphenol. It was first described in relation to lignan/phenylpropanoid-type phytochemicals, with isolation from a variety of plant sources, in particular, in relation to wounding and other physiologic changes.
Allorhizobium vitis is a plant pathogen that infects grapevines. The species is best known for causing a tumor known as crown gall disease. One of the virulent strains, A. vitis S4, is responsible both for crown gall on grapevines and for inducing a hypersensitive response in other plant species. Grapevines that have been affected by crown gall disease produce fewer grapes than unaffected plants. Though not all strains of A. vitis are tumorigenic, most strains can damage plant hosts.
The root inducing (Ri) -plasmid of Rhizobium rhizogenes is a plasmid capable of undergoing horizontal gene transfer of its transfer DNA (T-DNA), upon contact with a plant host. The T-DNA of the Ri-plasmid affects the plant host in such a way, that gene expression is altered, especially in regard to phytohormonal balances, metabolism and certain phenotypical characteristics.