1
Question
Select the option that correctly identifies the given statements as true (T) or false (F)
I. A bacteria that is helpful in creating transgenic plants is Agrobacterium
II. Silencing of mRNA or RNA interference (RNAi) technique is used to produce transgenic plants resistant to nematodes
III. The Ti plasmid is used for introducing foreign DNA in plants, and is found in Azotobacter
Select the option that correctly identifies the given statements as true (T) or false (F)
I. A bacteria that is helpful in creating transgenic plants is Agrobacterium
II. Silencing of mRNA or RNA interference (RNAi) technique is used to produce transgenic plants resistant to nematodes
III. The Ti plasmid is used for introducing foreign DNA in plants, and is found in Azotobacter
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Solution
The correct option is C I - T, II - T, III - F
Agrobacterium tumefaciens, a pathogen (bacteria) of various dicot plants is able to transfer a T-DNA (present in Ti plasmid) to convert normal plant cells into tumour inducing cells. The tumour inducing plasmid i.e., Ti plasmid of Agrobacterium tumefaciens is modified into a cloning vector that is not pathogenic to the plant but is capable of transferring the foreign DNA in the cell. It can be modified as per the requirement to insert the desired genes. Hence, it is helpful in creating transgenic plants.
The nematode Meloidogyne incognita, infects the roots of the tobacco plant and creates knot-like structures in the root. These knot-like structures affect efficient functioning of the roots and decrease the yield of the plant. The scientists adopted a unique strategy to prevent this infestation which was based on the process of RNA interference (RNAi). RNAi involves silencing of a specific mRNA.
The mechanism of RNA interference can be explained in the following steps:
The nematode-specific genes were introduced into the tobacco plant using Agrobacterium. Both sense and antisense RNA were produced from the nematode genes in the host cells. This two RNA’s being complementary to each other formed a double-stranded RNA (dsRNA). This long double-stranded RNA gets diced into small fragments with the help of an enzyme called dicer. These small fragments are known as siRNA or small interfering RNA.
The siRNAs enter into the body of the nematode during infection. The siRNAs bind to a specific protein and one of the strands from the double-stranded RNA is removed. The remaining strand with the protein binds to the mRNA target sequence of the nematode. This protein cleaves the mRNA and hence mRNA of the nematode is silenced. Due to this the proteins essential for survival of the nematode are not synthesised. This causes the death of the nematode and the transgenic tobacco plant gets itself protected from the parasite.
Ti plasmid is not found in Azotobacter. Azotobacter species are used as a biofertilizer for the cultivation of most agricultural crops such as cereals and pulses. These bacteria enrich the nutrient quality of the soil.
Agrobacterium tumefaciens, a pathogen (bacteria) of various dicot plants is able to transfer a T-DNA (present in Ti plasmid) to convert normal plant cells into tumour inducing cells. The tumour inducing plasmid i.e., Ti plasmid of Agrobacterium tumefaciens is modified into a cloning vector that is not pathogenic to the plant but is capable of transferring the foreign DNA in the cell. It can be modified as per the requirement to insert the desired genes. Hence, it is helpful in creating transgenic plants.
The nematode Meloidogyne incognita, infects the roots of the tobacco plant and creates knot-like structures in the root. These knot-like structures affect efficient functioning of the roots and decrease the yield of the plant. The scientists adopted a unique strategy to prevent this infestation which was based on the process of RNA interference (RNAi). RNAi involves silencing of a specific mRNA.
The mechanism of RNA interference can be explained in the following steps:
The nematode-specific genes were introduced into the tobacco plant using Agrobacterium. Both sense and antisense RNA were produced from the nematode genes in the host cells. This two RNA’s being complementary to each other formed a double-stranded RNA (dsRNA). This long double-stranded RNA gets diced into small fragments with the help of an enzyme called dicer. These small fragments are known as siRNA or small interfering RNA.
The siRNAs enter into the body of the nematode during infection. The siRNAs bind to a specific protein and one of the strands from the double-stranded RNA is removed. The remaining strand with the protein binds to the mRNA target sequence of the nematode. This protein cleaves the mRNA and hence mRNA of the nematode is silenced. Due to this the proteins essential for survival of the nematode are not synthesised. This causes the death of the nematode and the transgenic tobacco plant gets itself protected from the parasite.
Ti plasmid is not found in Azotobacter. Azotobacter species are used as a biofertilizer for the cultivation of most agricultural crops such as cereals and pulses. These bacteria enrich the nutrient quality of the soil.
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