Agrobacterium tumefaciens Ti plasmid

Morris, P.F., Bone, E., and Tyler, B.M., Chemotropic and contact responses of Phytophthora sojae hyphae to soybean isoflavonoids and artificial substrates. Plant Physiol, 117, 1171, 1998. Zerback, R., Dressier, K., and Hess, D., Flavonoid compounds from pollen and stigma of Petunia hybrida inducers of the vir region of the Agrobacterium tumefaciens Ti plasmid. Plant Scl, 62, 83, 1989. 

Hooykaas-van Slogteren, G.M.S., Hooykaas, P.J.J. Schilperoort, R.A. (1984). Expression of Ti plasmid genes in monocotyledonous plants infected with Agrobacterium tumefaciens. Nature, 311, 763-4. 

A. M. Ashby, M. D. Watson, and C. H. Shaw, A Ti-plasmid determined function is responsible for cheinotaxis of Agrobacterium tumefaciens towards the plant wound product acetosyringone, FEMS Microbiology Letters 47 189 (1987). 

There exist a variety of vectors for cloning into eukaryotic systems, ranging from yeast (Saccharomyces as well as Pichia) through insect cells (Baculovims) and plants (Ti plasmid from Agrobacterium tumefaciens) to mammalian cells (transfected by viral or mammalian vectors). As expression in eukaryotic hosts is less efficient than bacterial expression in terms of yield and time and more complicated in terms of vector structure and culture conditions, such eukaryotic expression systems are only used for genes whose proteins require posttranslational modification which is not possible in bacteria. Yeast is the preferred option as a relatively easily culturable single-cell system but posttranslational modification capabilities is limited. The additional complexity can be circumvented in part by exploiting the ability of eukaryotic vectors to act as shuttle vectors, which can be shuttled between two evolutionarily different hosts. Thus, eukaryotic vectors can be replicated and analyzed in bacteria and transfected into eukaryotic cells for expression of the recombinant product. 

Piper, K.R., Beck vonBodman, S., FarrandS.K. Conjugation factor of Agrobacterium tumefaciens regulates Ti plasmid transfer by autoinduction. Nature 1993 362 448-450. 

Figure 13. Agrobacterium tumefaciens, the natural transformation system for plants. The bacterium contains a circular piece of DNA, the Ti-plasmid. The bacterium infects a dicotyledonous plant and transfers the T-DNA from the Ti-plasmid to the plant chromosomal DNA causing a tumor to form. The tumor is called a "crown gall". The gall, or teratoma, can be removed from the plant and placed into culture on medium without exogenous hormones.

Figure 6.33. Tumors in Plants. Crown gall, a plant tumor, is caused by a bacterium Agrobacterium tumefaciens) that carries a tumor-inducing plasmid (Ti plasmid). 

Fig. 1. A widely used method for DNA transfer to plants makes use of the natural DNA transfer system of Agrobacterium tumefaciens. Virulence genes located on the Ti plasmid (vir-region) are part of the machinery by which the T-DNA-protein complex (T-complex) is transferred from agrobacterium to the plant cell nucleus. Here the T-DNA is inserted into the plant genome.

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