Question

Plants are naturally infected by a soil bacteria that scientists use for plant transformation.

i) What is the name of these bacteria, and what do they contain that is useful for plant transformation?

ii) Explain how foreign genes become a permanent part of the plant cell using these bacteria.

Answer 1

Answer (i)

Agrobacterium tumifaciens is a soil bacteria which infects plants and causes crown gall disease in plants. Bacteria transfers it's T-DNA (located on Ti plasmid) into the plants cell through type IV secretion system (T4SS) T-DNA contains gene for the biosynthesis of auxin and cytokinin which increase the cell division in plants and leads to tumor formation. T- DNA can modified as the gene responsible for crown gall disease can replaced with the gene we have to transfer to the plant cell or we can say with the gene of interest.

(ii) There are vir (virulence) genes also present on Ti plasmid which helps in transfer of T-DNA to the host cell. First of all bacteria attached to the plant cell and sense the plant signals in the form of sugars, phenolic or acid. Vir A and G sense and transduce the signals and further activation of other vir genes. Vir B ,D2 and D4 helps in generation of T-DNA and creation of Type 4 secretion system (T4SS) for the transport of T- DNA from bacterial cell to plant cell. After transfer to the plant cell host factors along with vir E2 and F helps in nuclear import of T-DNA along with foreign gene. And foreign gene get integrated to the plant genome permanently.

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