Figure 1.

Activation tagging identifies Arabidopsis mutants that are hypersusceptible to Agrobacterium transformation (hat mutants). Root segments of wild-type (ecotype Wassilewskija) and T-DNA activation-tagged mutants (Weigel et al., 2000) were inoculated with the tumorigenic strain A. tumefaciens A208 at low inoculum density (10⁶ colony forming units/mL). After 2 d of cocultivation, the root segments were transferred to Murashige and Skoog medium lacking phytohormones and tumors were allowed to develop (Zhu et al., 2003b). The plates were photographed after 4 weeks. Note the larger and more numerous tumors formed on root segments of the hat1 mutant line, compared to the tumors formed on wild-type roots. The hat1 mutant has a T-DNA activation tag inserted into a cellulose synthase-like gene. Expression of a neighboring UGT gene is greatly enhanced in the hat1 mutant.