Ti plasmid

The structure of the Ti plasmid

A Ti or tumour inducing plasmid is a plasmid that often, but not always, is a part of the genetic equipment that Agrobacterium tumefaciens and Agrobacterium rhizogenes use to transduce its genetic material to plants. The Ti plasmid is lost when Agrobacterium is grown above 28 °C. Such cured bacteria do not induce crown galls, i.e. they become avirulent. pTi and pRi share little sequence homology but are functionally rather similar. The Ti plasmids are classified into different types based on the type of opine produced by their genes. The different opines specified by pTi are octopine, nopaline, succinamopine and leucinopine.

The plasmid has 196 genes that code for 195 proteins. There is one structural RNA. The plasmid is 206,479 nucleotides long, the GC content is 56% and 81% of the material is coding genes. There are no pseudogenes.

The modification of this plasmid is very important in the creation of transgenic plants.

Virulence region

Genes in the virulence region are grouped into the operons virABCDEFG, which code for the enzymes responsible for mediating conjugative transfer of T-DNA to plant cells.[1]

Characteristic features

See also

References

  1. Scott E.Stachelt; Eugene W.Nester (1986). "The genetic and transcriptional organization of the vir region of the A6 Ti plasmid of Agrobacterium tumefaciens". The EMBO Journal. 5 (7): 1445–1454. PMC 1166964Freely accessible. PMID 3017694.
  2. 1 2 3 4 5 Schrammeijer, B., Beijersbergen, A., Idler, K.B., Melchers, L.S., Thompson, D.V., Hooykaas, P.J.J. (2000). "Sequence analysis of the vir-region from Agrobacterium tumefaciens octopine Ti plasmid pTi15955". Journal of Experimental Botany. 51 (347): 1167–1169. doi:10.1093/jexbot/51.347.1167. PMID 10948245.
  3. Reconstitution of Acetosyringone-Mediated Agrobacterium tumefaciens Virulence Gene Expression in the Heterologous Host Escherichia coli. Scott M. Lohrke, Hongjiang Yang, and Shouguang Jin, J Bacteriol. 2001 June; 183(12): 3704–3711, doi:10.1128/JB.183.12.3704-3711.2001
  4. 1 2 3 Alexander N. Glazer; Hiroshi Nikaidō (2007). Microbial biotechnology: fundamentals of applied microbiology. Cambridge University Press. ISBN 0-521-84210-7.
  5. Hamilton CM, Lee H, Li PL, et al. (March 2000). "TraG from RP4 and TraG and VirD4 from Ti plasmids confer relaxosome specificity to the conjugal transfer system of pTiC58". J. Bacteriol. 182 (6): 1541–8. doi:10.1128/jb.182.6.1541-1548.2000. PMC 94450Freely accessible. PMID 10692358.

External links

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