VirA and VirG form a two component signaling system during Agrobacterium infection in plants. In an experiment, VirG was mutated resulting in…
VirA and VirG form a two component signaling system during Agrobacterium infection in plants. In an experiment, VirG was mutated resulting in nonfunctional VirG protein. Which one of the following consequences is most likely?
Select an option to attempt
Correct Answer: Option B
Explanation
VirA-VirG two-component system in Agrobacterium:Agrobacterium tumefaciens virulence signal transduction uses a two-component system:1. VirA: the sensor histidine kinase (located in the bacterial inner membrane).• Perceives phenolic signals (e.g., acetosyringone) released from wounded plant cells.• Upon sensing, VirA AUTOPHOSPHORYLATES on a conserved histidine residue.• Transfers the phosphate to VirG.2. VirG: the response regulator (transcription factor).• When phosphorylated (by VirA), VirG activates transcription of all vir genes (virB, virC, virD, virE, virF, virH).• vir gene products mediate T-DNA processing and transfer.If VirG is non-functional:• VirA can still perceive and autophosphorylate normally.• But without functional VirG to receive the phosphate, downstream vir genes are NOT activated.• Signal is PERCEIVED but NOT TRANSDUCED → no virulence.Answer: VirA (sensor) perceives plant signals normally; non-functional VirG cannot transduce the signal → virulence blocked.