Q.30 Agrobacterium rhizogenes is used to genetically engineer the plant because of the
following statement
1. It contains a Ti plamid
2. It causes gene transfer to plants
3. It infects all types of plants
4. Infects plants and produce a good root system
Agrobacterium Rhizogenes Genetic Engineering
Agrobacterium rhizogenes enables plant genetic engineering through its unique plasmid capabilities. The correct answer is option 2: It causes gene transfer to plants.
Correct Answer
Agrobacterium rhizogenes transfers T-DNA from its Ri plasmid (root-inducing plasmid) into plant genomes, integrating genes that promote hairy root formation while enabling foreign DNA insertion for transformation. This natural gene transfer mechanism, similar to A. tumefaciens’ Ti plasmid, makes it a key tool for stable plant genetic engineering. Disarmed Ri vectors retain vir genes for efficient T-DNA delivery without oncogenic effects.
Option Analysis
| Option | Statement | Explanation |
|---|---|---|
| 1. It contains a Ti plasmid | Ti plasmid | Incorrect. A. rhizogenes has an Ri plasmid, not Ti (which is specific to A. tumefaciens for tumors). Ri shares vir homology but differs in T-DNA effects. |
| 2. It causes gene transfer to plants | Gene transfer | Correct. Ri plasmid’s T-DNA and vir genes drive DNA transfer/integration into plants for engineering. |
| 3. It infects all types of plants | All plants | False. Limited to dicots; less effective on monocots compared to A. tumefaciens strains. |
| 4. Infects plants and produce a good root system | Root system | Partial truth but incomplete. Ri induces hairy roots via auxin genes, useful for transformation but not the primary engineering reason. Gene transfer is the core mechanism. |
Application in Plant Biotech
A. rhizogenes produces “hairy roots” ideal for secondary metabolite production and gene expression studies. Binary vectors combine Ri vir regions with custom T-DNA for targeted engineering in species like tomato and tobacco. For exams, note Ri vs. Ti distinction: roots vs. tumors.
