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.

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.

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