Question

How has the use of Agrobacterium as vectors helped in controlling Meloidogyne incognita infestation in tobacco plants? Explain in the correct sequence.

Answer 1

Transgenic plants are those plants into which one or more than one genes from other species which have been introduced into the genome by using genetic engineering processes. This technique is used to introduce a new trait to the plant.

Complete answer:
Agrobacterium tumefaciens belongs to a genus of Gram-negative bacterium, which is a soil phytopathogen (an organism that is pathogenic to plant) that naturally infects the plant wound site by causing tumor in plants i.e. crown gall disease. Agrobacterium has the ability to work as a vector for introducing new or foreign genetic material into the plant and regenerating transgenic plants.
Meloidogyne incognita (or root-nematode) a plant-parasitic roundworm grows in soil in areas with hot climatic conditions. Larvae of root-knot nematodes invade the roots of the tobacco plant, which allows the root-knot galls to form that take out nutrients from the plant.
To prevent this infection of tobacco plants RNA interference process was adopted. RNA interference involves the silencing of specific mRNA due to a complementary ds-RNA molecule (double-stranded RNA) which binds and prevents the translation of the mRNA which is known as RNA silencing. This complementary ds-RNA can be obtained from the infection due to the virus-containing RNA genome. With the help of Agrobacterium as a vector, the root-knot nematode specific genes were inserted into the host plant so that they produce sense and antisense RNA in the host cells. Two complementary RNAs form double-stranded RNA which initiates RNAi (RNA interference), thus silencing the specific mRNA of the nematode.

Note: Agrobacterium uses a horizontal gene transfer mechanism i.e. transmission of genetic material between non-mating species by processes other than fertilization to transfer genes. Those plants that are infected by the root nematode exhibit water and nutrient stress, yellowing, and wilting.