Q.58. In relation to Agrobacterium mediated genetic engineering in plants, match the following in
CORRECT combination
Gene name
P. virA
Q. virB
R. virD1
S. vir 𝐺
Function
i. Acetosyringone receptor
ii. Conjugal tube formation
iii. Topoisomerase
iv. Inducer of all vir operons
v. Octopine synthesis
(A) P-iv, Q-iii, R-ii, S-v
(B) P-ii, Q-i, R-iii, S-v
(C) P-i, Q-ii, R-iii, S-iv
(D) P-iii, Q-i, R-ii, S-iv

Agrobacterium-mediated genetic engineering relies on specific vir genes for T-DNA transfer into plants. The correct matching identifies their precise functions in this process.

Correct Answer
The correct option is (C) P-i, Q-ii, R-iii, S-iv. This pairs P. virA with acetosyringone receptor (i), Q. virB with conjugal tube formation (ii), R. virD1 with topoisomerase (iii), and S. virG with inducer of all vir operons (iv).​

Vir Genes Functions
VirA encodes a sensor kinase that detects plant phenolic signals like acetosyringone, acting as the receptor to initiate the virulence cascade. VirB proteins form a type IV secretion system, analogous to a conjugal tube, for exporting T-DNA and proteins into plant cells. VirD1 teams with VirD2 as an endonuclease with topoisomerase-like activity to process T-DNA borders. VirG, once phosphorylated by VirA, serves as the transcriptional activator inducing all other vir operons.​

Options Analysis
Option (A) P-iv, Q-iii, R-ii, S-v mismatches virA (not inducer), virB (not topoisomerase), virD1 (not tube), and assigns octopine synthesis (T-DNA gene, not vir) to virG.
Option (B) P-ii, Q-i, R-iii, S-v incorrectly links virA to tube formation, virB to receptor, and virG to octopine.
Option (D) P-iii, Q-i, R-ii, S-iv wrongly attributes topoisomerase to virA, receptor to virB, and tube to virD1.
Option (C) alone aligns all functions accurately based on established Agrobacterium biology.​