Figure 6.

Arabidopsis Plants Expressing VirE2 Are Hypersensitive to Bleomycin and Show Enhanced Stable Transformation Efficiency.

(A) Response of transgenic VirE2-YFP–expressing lines to bleomycin. One-week-old healthy seedlings were transferred to MS medium containing varying concentrations of bleomycin, and the response was photographed after 21 d. The box indicates the hypersensitivity of VirE2-YFP–expressing lines 8 and 11 over Col-0 control.

(B) Quantification of DNA damage by comet assay. Micrographs of nuclei in Col-0 and VirE2-YFP–expressing lines by neutral comet assay with or without bleomycin (5 μg/mL) treatment (top panel). The fraction of DNA in comet tails was visualized by SYBR Green staining and quantified with CometScore software (bottom panel). Data are presented as mean ± sd of 150 randomly selected cells per slide. Asterisks indicate a significant difference between Col-0 and VirE2-YFP–expressing lines according to Student’s t test (P < 0.05). WT, the wild type.

(C) Frequency of tumor and transgenic calli formation from root segments infected with low concentration (1 × 10⁷ cfu/mL) of tumorigenic strain Agrobacterium A208 and disarmed strain Agrobacterium GV3101 (pCAS1), respectively. Data are presented as mean ± sd (n = 3) from three replicates with 50 root segments per treatment. Asterisks indicate a significant difference between Col-0 and VirE2-YFP–expressing lines according to Student’s t test (P < 0.05).

(D) Representative plates of root tumor transformation assay from Col-0 versus VirE2-YFP–expressing lines. Root segments of wild-type Col-0 and VirE2-YFP–expressing lines were infected with a low concentration (1 × 10⁷ cfu/mL) of tumorigenic strain Agrobacterium A208. Tumors on root segments were photographed 4 weeks after infection.

(E) Root segments of Col-0 and VirE2-YFP–expressing lines were inoculated with strain Agrobacterium GV3101 harboring pBISN1, and blue spots on roots were counted at 2 and 12 d after staining with X-gluc.

(F) Root segments of Col-0 and VirE2-YFP–expressing lines were inoculated with strain Agrobacterium GV3101 harboring pKM1. Root segments were stained with X-gluc, and blue spots were counted at 5, 15, and 25 DAI. In (E) and (F), data are presented as mean ± sd (n = 3) from three replicates with 50 root segments per treatment. Asterisks indicate a significant difference between Col-0 and VirE2-YFP–expressing lines according to Student’s t test (P < 0.05; see Supplemental Figure 7 online).