The Ti-plasmid and Plant Molecular Biology.

Agrobacterium-mediated plant transformation also is the major method for generating transgenic plants for research and biotechnology purposes. Agrobacterium species have the natural ability to conduct interkingdom genetic transfer from bacteria to eukaryotes, including most plant species, yeast, fungi, and even animal cells.

From the research point of view, Agrobacterium is an important plant pathogen that is required for biological genetic transformation in plants and Agrobacterium transformation technologies were developed by leading international crop science players such as Bayer and others.

Updated information of mechanisms for T-DNA transfer to plant cells by Agrobacterium tumefaciens is provided, focused on the role played by the different components of the virulence system.

In the Ti-plasmid, there are genes encoding for plant hormones such as auxin and cytokinin synthesis, which will induce tumour tissue in plants. However, for vaccine production, these genes will be deleted to form disarmed Ti-plasmid and heterologous gene is inserted forming a recombinant plasmid vector.

Research Organization, P.O. Box 6,. harboring Ti-plasmid pGV3850 (16), was used as host for the. Strain C58NT1, which does not contain a Ti plasmid (17), was used as control.Agrobacterium strains carrying Ti plasmids with individual vir loci inactivated by Tn3-HoHo1 transposon insertions were described previously (18).

The disarmed Ti plasmid in Agrobacterium synthesize vir gene products that are involved in transfering target gene present between two border sequences from bacteria to plant cell. Co-integrative Vector: In this approach, the vector is designed to co-integrate into the T-region of the Ti plasmid.

In fact, Agrobacterium attaches to and genetically transforms several types of human cells. The researchers found that in stably transformed HeLa cells, the integration event occurred at the right border of the Ti plasmid's T-DNA, exactly as would happen when it is being transferred into a plant cell genome.

Updated information of mechanisms for T-DNA transfer to plant cells by Agrobacterium tumefaciens is provided, focused on the role played by the different components of the virulence system. The general assessments for the establishment of efficient transformation protocols are discussed with an emphasis in the application of this methodology to monocotyledonous plants.

On the Ti plasmid, there is a DNA fragment called T-DNA (transfer DNA) which contains the gene causing crown galls development. Plant cells have genes to code for the production of auxin and cytokinin, the two plant hormones which are used as energy sources by Agrobacterium.

The capability of Agrobacterium to integrate its own DNA into the host genome is predominantly determined by large Ti (tumor inducing) plasmid (Gelvin, 2003). Indeed, bacterial strains that are devoid of Ti plasmid are not virulent, i.e. they do not induce tumors. Moreover, virulence can be restored upon Ti plasmid acquisition.

This review chronicles the development of the plant binary vectors of Ti plasmid in Agrobacterium tumefaciens during the last 30 years. A binary vector strategy was designed in 1983 to separate the T-DNA region in a small plasmid from the virulence genes in avirulent T-DNA-less Ti plasmid. The small plant vectors with the T-DNA region have been simply now called binary Ti vectors.

Introduction. Agrobacterium tumefaciens is the only known organism that routinely mediates inter-Kingdom gene transfer 1, 2, 3, and, as such, has been exploited as a natural vector for the incorporation of foreign genes into higher plants .Briefly, when virulent A. tumefaciens infects a wound site, the virulence (vir) genes on the resident tumor-inducing (Ti) plasmid are expressed.