(A) Schematic structure of the VBF expression cassette in pEX-VBF. VBF expression in Agrobacterium is directed by the virF promoter, and VBF export from the bacterial cell is promoted by the VirE3 export signal (EX) fused to the C-terminus of VBF. (B) Representative images of tumors developed on tomato stems following infection by VirF(-) Agrobacterium strains LBA1517, LBA1517 that expresses VBF from pEX-VBF, or LBA1517 that expresses VirF from pEX-VirF. (C) Quantitation of tumorigenicity of LBA1517 (black bar), VBF-expressing LBA1517 (gray bar), or VirF-expressing LBA1517 (positive control, white bar) Agrobacterium strains in tomato plants. Standard deviations are indicated.