Transcription activator that binds specifically to the VIP1 response elements (VREs) DNA sequence 5'-ACNGCT-3' found in some stress genes (e.g. TRX8 and MYB44), when phosphorylated/activated by MPK3. Required for Agrobacterium VirE2 nuclear import and tumorigenicity. Promotes transient expression of T-DNA in early stages by interacting with VirE2 in complex with the T-DNA and facilitating its translocation to the nucleus, and mediates stable genetic transformation by Agrobacterium by binding H2A histone. Prevents cell differentiation and shoot formation. Limits sulfate utilization efficiency (SUE) and sulfate uptake, especially in low-sulfur conditions (PubMed:11432846, PubMed:12124400, PubMed:15108305, PubMed:15824315, PubMed:17947581, PubMed:19820165, PubMed:20547563). Plays a role in osmosensory response by binding to the 5'-AGCTGT/G-3' DNA sequence found in the promoters of the hypoosmolarity-responsive genes CYP707A1 and CYP707A3 (PubMed:25093810, PubMed:22452852). Involved in the negative regulation of touch-induced root bending and salt-dependent root bending (PubMed:27208231, PubMed:30010769, PubMed:31504762). Forms homomultimers. Interacts with Agrobacterium tumefaciens VirE2 and mediates its translocation to the host nucleus. Binds to VIP2. Forms a complex made of Agrobacterium VirE2, VIP1, VIP2 and single-stranded DNA (ssDNA). The interaction with KAP1 mediates its nuclear import. Binds to the H2A histone RAT5. Interacts with MPK3 and Agrobacterium virF. Forms a complex made of VIP1, VBF and Agrobacterium virE2. Interacts with SCF(VBF) E3 ubiquitin ligase complex. Binds directly to VBF. Forms heterodimers with BZIP34 AND BZIP61. Confined to nucleus when phosphorylated (PubMed:17947581). Transiently accumulates in the nucleus when cells are exposed to hypoosmotic conditions (PubMed:25093810, PubMed:31504762). Mostly expressed in dividing cells, present in leaves, roots and seedlings. Transcriptionally activated during the acquisition of pluripotentiality (in protoplasts) by pericentromeric chromatin decondensation and DNA demethylation. Targeted to degradation by the proteasome by VBF and Agrobacterium virF in SCF(VBF) and SCF(virF) E3 ubiquitin ligase complexes after mediating T-DNA translocation to the nucleus. Phosphorylated by MPK3. This phosphorylation promotes nuclear localization. Enhanced low sulfur tolerance with higher rate of sulfate uptake at low sulfate levels. Improved tolerance to heavy metal (e.g. CdCl(2)) and oxidative stress (e.g. paraquat). Belongs to the bZIP family.