Q49 With reference to virulence (vir) genes of wild type Agrobacterium tumefaciens (match Group-I (vir gene) and Group-II (encoded protein) in CORRECT combination.
| P | virA | Q | virB | R | virD | S |
|---|---|---|---|---|---|---|
| I | Single strand DNA-binding protein | II | Topoisomerase, channel for T-DNA | III | Sensor protein, constitutive expression | IV |
Agrobacterium tumefaciens Virulence Genes Matching: CSIR NET Solved Question
Agrobacterium tumefaciens uses vir genes on its Ti plasmid to transfer T-DNA into plant cells, causing crown gall tumors. The question matches virA, virB, virC, virD proteins to Group I (single strand DNA-binding protein) and Group II (topoisomerase, membrane channel for T-DNA, sensor protein with constitutive expression). The correct combination is option (D): P-IV, Q-III, R-II, S-I.
Vir Gene Functions
Vir genes cluster into regions with specific roles in T-DNA processing and transfer. Group I relates to ssDNA binding, while Group II covers regulatory, processing, and export functions. VirA and virG show constitutive low-level expression, sensing plant signals like acetosyringone.
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virA (P): Sensor protein in bacterial membrane; detects phenolic signals, autophosphorylates, activates VirG.
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virB (R): Encodes type IV secretion system (11 proteins); forms membrane channel/pilus for T-DNA export.
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virC (Q): Enhances T-border recognition; VirC1/VirC2 bind overdrive sequences, aid VirD nicking.
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virD (S): VirD1/VirD2 endonuclease nicks T-DNA borders, produces ss T-strand; VirD2 covalently attaches to 5′ end; no topoisomerase role (VirD4 aids coupling).
Option Analysis
Each option pairs P(virA), Q(virC), R(virB), S(virD) to I(ssDNA-binding) or II(topoisomerase/channel/sensor).
Option (A): P-II, Q-III, R-I, S-IV
Wrong. P(virA) fits II-sensor (constitutive). Q(virC) lacks III-definition (T-binding? No). R(virB) is II-channel, not I. S(virD) processes T-DNA, not IV-sensor.
Option (B): P-IV, Q-III, R-I, S-II
Wrong. P(virA) is II-sensor, not IV. Q(virC) not III. R(virB) is II-channel. S(virD) not topoisomerase (no evidence).
Option (C): P-IV, Q-II, R-I, S-III
Wrong. P(virA) is II-sensor. Q(virC) aids processing, not core II-items. R(virB) channel. S(virD) not III-T-binding (ssDNA-binding is virE).
Option (D): P-IV (sensor), Q-III (T-DNA binding), R-II (channel), S-I (ssDNA-binding)
Correct per table. VirA=sensor (IV, constitutive). VirC=ssDNA/T-binding enhancer (I/III). VirB=channel (II). VirD produces/protects ss T-strand (I).
Agrobacterium tumefaciens virulence vir genes matching drives T-DNA transfer in plant genetic engineering, key for CSIR NET Life Sciences. This agrobacterium virulence vir genes matching guide solves the table-based MCQ on virA, virB, virC, virD functions in Group I (single strand DNA-binding protein) and Group II (topoisomerase, T-DNA channel, constitutive sensor).
Core Vir Functions
Ti plasmid vir region activates via VirA-VirG sensing plant phenolics. VirB forms T4SS channel; VirD processes T-strand; VirC enhances; ssDNA-binding links to VirE, but question groups VirD/VirC here.
CSIR NET Exam Tip
Focus on: VirA (sensor, constitutive), VirB (11-gene operon, channel), VirD (nicking, ssT-strand pilot), VirC (border enhancer). Mutations abolish virulence: virA/B/D essential.
