The statement that is NOT true is (4):
“The T‑DNA, after becoming coated with VirF binds to phosphorylated VIP1, which allows the complex to enter the plant’s nucleus.”

The T‑DNA is actually coated mainly with VirE2, not VirF; VIP1 interacts with VirE2 to help nuclear import, while VirF later targets VirE2/VIP1 for proteasomal degradation.​

Why options (1)–(3) are true

1. VirA/VirG perceive acetosyringone – True

• VirA is a membrane histidine kinase that detects plant phenolics such as acetosyringone, then phosphorylates the response regulator VirG.​

• Activated VirG induces vir gene transcription; together they form the two‑component system sensing acetosyringone.

2. VirB forms a connection and transfers T‑DNA – True

• VirB proteins build the type IV secretion system (T4SS) and T‑pilus that connect Agrobacterium to the plant cell and translocate the VirD2–T‑strand complex and effector proteins.​

3. T‑DNA is excised and bound to VirD2 – True

• VirD1/VirD2 nick the T‑DNA border sequences; the resulting single‑stranded T‑strand remains covalently linked at its 5′ end to VirD2, forming the core of the T‑complex.​

Why option (4) is false

4. “T‑DNA, after becoming coated with VirF, binds phosphorylated VIP1 for nuclear entry” – Not true

• The T‑DNA in the plant cytoplasm is mainly coated by VirE2, a single‑stranded DNA‑binding protein, together with VirD2; this nucleoprotein is called the T‑complex.​

• Plant protein VIP1 binds VirE2, and this VirE2–VIP1 interaction, along with VirD2 NLSs, mediates nuclear import of the T‑complex.​

• VirF is an F‑box effector that later targets VirE2/VIP1 and other proteins for proteasomal degradation to uncoat T‑DNA; it does not “coat” T‑DNA or partner with VIP1 for nuclear entry.​

Thus, statement (4) misassigns VirF’s role and confuses it with VirE2, making it the only incorrect option.

SEO‑oriented introduction (for article use)

During Agrobacterium infection of plant cells, phenolic signals such as acetosyringone are perceived by the VirA/VirG system, the VirB type IV secretion machinery transfers the VirD2‑linked T‑strand, and once inside the plant cell the DNA is coated by VirE2, which interacts with plant VIP1 to promote nuclear import. The protein VirF, in contrast, functions later to remove VirE2/VIP1 via the proteasome, so the statement that T‑DNA is coated with VirF and enters the nucleus via VirF–VIP1 binding is not true.