Interactions and DNA transfer between Agrobacterium tumefaciens , the Ti-plasmid and the plant host (original) (raw)
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Plant Molecular Biology, 1984
A shooty tumor induced by a shooter mutant of an octopine strain of Agrobacterium tumefaciens was cloned. One clone obtained (TS038) behaved aberrantly in that it grew as a shooty tumor tissue on phytohormone free medium, but did not contain octopine synthase activity. In line TS038 the genes for octopine synthase and for the enzymes involved in agropine and mannopine synthesis were present, but were not transcribed. However, the above genes became active in TS038 tumor shoots after grafting as well as after treatment with the hypomethylating agent 5-azacytidine. After an unusually long incubation period in the growth cabinet shoot cultures appeared to have developed small shoots from the top of the leaves. This unusual form of differentiation was found to be accompanied by the induction of octopine synthase activity.
Journal of General Microbiology, 1977
A mutant of A . tumefaciens strain ~6~3 , carrying the R factor RP4, was able to transfer its TI plasmid to various avirulent Agrobacterium strains and to a strain of Rhizobium. Strains carrying the TI(~6s3) plasmid were selected by their ability to utilize octopine. The isolates were able to induce tumours and exclude phage API . The tumours induced on Kalanchoe daigremontiana were rough and contained
Delivery of T-DNA from the Agrobacterium tumefaciens chromosome into plant cells
The EMBO journal, 1984
The intact T-region of the B6Ti plasmid of Agrobacterium tumefaciens was stepwise cloned into a site in transposon Tn3. In this way a suitable vehicle (Tn1882) was obtained for translocating the T-region to different replicons, i.e., to other plasmids or the chromosome. The IncP plasmid R772::Tn1882 conferred tumorigenicity on Agrobacterium if the virulence genes were provided in trans in the same cell. This result showed that the T-region present on Tn1882 was transferred efficiently to plant cells. Normal tumor development also occurred if the T-region was placed in the chromosome of A. tumefaciens and an R' plasmid was present carrying virA-E or virA-F. We conclude that the plasmid location of the T-region is not a prerequisite for transfer to the plant cell. The apparently normal delivery of the T-DNA from a bacterial chromosomal location supports a model involving a processing step within Agrobacterium effecting transfer of the T-region as a separate entity.
Agrobacterium tumefaciens Transformation of Monocotyledons
Crop Science, 1995
Agrobaclerium tumefaciens (Smitb and Townsend, 1907) bas been an extremely useful vector to transfer foreign genes into dicotyledonous plants. Monocotyledonous plants, particularly the cereals, have been considered outside the host range for A. tumefaciens, which has necessi tated the development of other transformation systems sucb as naked DNA delivery to protoplasts and, most recently, microprojectile bom bardment delivery of DNA to cells and tissues. Both systems have worked, but there are still many difficulties encountered in routine transrormation of any monocotyledon. Recently, there has been re newed interest in using the A. tumefacuns system to transform econom ically important grasses and other monocotyledons. This paper exam ines the literature and steps involved in transformation of monocotyledons by A. tumefaciens. The many recent advances in understanding the biology of the infection process (meristematic target cell, vir gene inducing compounds, and wide host range strains of A. tumefaciens), and availability or more monocotyledon gene promot ers and improved selectable markers greatly improve the opportunities of developing monocotyledon transformation systems with A. tume/a ciens.
New Approaches to Agrobacterium tumefaciens-Mediated Gene Transfer to Plants
Genetic Engineering - An Insight into the Strategies and Applications, 2016
Agrobacterium tumefaciens, a plant pathogen, is commonly used as a vector for the introduction of foreign genes into plants and consequent regeneration of transgenic plants. A. tumefaciens naturally infects the wound sites in dicotyledonous plants and induces diseases known as crown gall. The bacterium has a large plasmid that induces tumor induction, and for this reason, it was named tumor-inducing (Ti) plasmid. The expression of T-DNA genes of Ti-plasmid in plant cells causes the formation of tumors at the infection site. The molecular basis of Agrobacterium-mediated transformation is the stable integration of a DNA sequence (T-DNA) from Ti (tumor-inducing) plasmid of A. tumefaciens into the plant genome. A. tumefaciens-mediated transformation has some advantages compared with direct gene transfer methods such as integration of low copy number of T-DNA into plant genome, stable gene expression, and transformation of large size DNA segments. That is why manipulations of the plant, bacteria and physical conditions have been applied to increase the virulence of bacteria and to increase the transformation efficiency. Preculturing explants before inoculation, modification of temperature and medium pH, addition chemicals to inoculation medium such as acetosyringone, changing bacterial density, and cocultivation period, and vacuum infiltration have been reported to increase transformation. In this chapter, four new transformation protocols that can be used to increase the transformation efficiency via A. tumefaciens in most plant species are described.