Ti-Plasmid : Features, Diagram and Uses

Ti-plasmid, short for tumour-inducing plasmid, is an extrachromosomal molecule of DNA found commonly in the plant pathogen Agrobacterium tumefaciens. It is also found in other species of Agrobacterium such as A.rubi, A.vitis and A.rhizogenes.

History

Agrobacterium is a gram negative bacteria that belongs to the class Alphaproteobacteria. It is one of the pathogenic species belonging to this class. Other non-pathogenic and plant symbiotic species include Caulobacter, Rhodobacter and Rhizobium.

The Ti-plasmid in the bacteria is known to induce crown gall disease in plants by transferring crucial regions from the plasmid. These crucial regions were seen to modify the plant cells into a tumour to produce synthetic plant hormones and cause crown gall. This led the scientists to believe that there is a scope for bioengineering techniques to modify the plants using Ti-plasmid for our own use.

Well Labelled Diagram of Ti Plasmid

Features of Ti Plasmid

• Virulence Region: The virulence region codes for virulence genes that are responsible for the transfer of T-DNA to the plant cells and also recruiting various effector proteins for infecting the plant cells.
• T-DNA: The T-DNA region is the crucial region that gets transferred to the plant cell for infection. It is approximately 15-20 kbp in length and is transferred to the plant cell via means of genetic recombination.
• Opine Catabolism: The opine catabolism region is the region from where the bacteria sources its nutrients for the whole process. Opines are derivatives of amino acid or sugar phosphates that can be catabolized to use in the form of nutrients. The types of opines found in Ti-plasmid are nopaline and octopine types.
• Origin of Replication: The origin of replication is the region where replication of the plasmid is initiated.

Uses in Bioengineering

• The ability of the Ti-plasmid to modify the plant cells has been taken advantage of for the production of transgenic plants.
• The plasmids have been modified into a cloning vector now which are no more pathogenic to plants. They are being used to transfer genes of our interest into the plant and produce plants with better quality and quantity.
• It is therefore known as ‘nature’s genetic engineer’

Visit BYJU’S Biology for more information.

Also Read:

• Difference Between Plasmid DNA And Chromosomal DNA
• Difference between Plasmid and Vector
• Difference between Cloning Vector and Plasmid Vector