Which one of the following microorganisms is used as a cloning vector to deliver the genes of interest into a variety of plants?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Agrobacterium tumifaciens
A cloning vector is a carrier that delivers a gene of interest into a host cell. Agrobacterium tumifaciens is a pathogen of several dicot plants. It delivers a piece of DNA called T-DNA into plant cells and turns them into a tumour. Its Ti plasmid has been modified so that it no longer causes disease, but it can still deliver our genes into a variety of plants.
(1) Bacillus thuringiensis — Incorrect. It is the source of the Bt toxin gene. It is not the vector that carries genes into plants.
(2) Rhino viruses — Incorrect. They cause the common cold in humans. They are not used as vectors for plants.
(3) Agrobacterium tumifaciens — Correct. Its modified Ti plasmid is the cloning vector for plants.
(4) Nucleopolyhedrovirus — Incorrect. It is a virus that attacks insects. It is used to control insect pests, not to carry genes into plants.
NCERT Extract:
Cloning Vectors – “… A better understanding of the art of delivering genes by pathogens in their eukaryotic hosts has generated knowledge to transform these tools of pathogens into useful vectors for delivering genes of interest to humans. The tumor inducing (Ti) plasmid of Agrobacterium tumifaciens has now been modified into a cloning vector which is no more pathogenic to the plants but is still able to use the mechanisms to deliver genes of our interest into a variety of plants.”