Starvation Treatment Increases Transient Expression Frequency of a Foreign Gene Introduced into Eustoma grandiflorum Root Tissues by Particle Bombardment

Root explants of Eustoma grandiflorum were bombarded with plasmid pBI221 harboring the uidA gene encoding β-glucuronidase (GUS) driven by a cauliflower mosaic virus 35S promoter, and the effects of pre- and post-bombardment culture in various starvation media on the number of blue spots of GUS-expressing cells were studied. It was found that pre- and post-bombardment culture in nitrogen-depleted media increased the expression frequency of the transgene, by 4- to 8-times that of the control, and that 3-h pre-culture in the nitrogen-depleted medium gave the highest expression frequency.