Microprojectile-mediated transient and integrative transformation of rice embryogenic suspension cells: effects of osmotic cell conditioning and of the physical configuration of plasmid DNA

Microprojectile-mediated transient and integrative transformation Frequenci es in rice (Oryza sativa cv. Taipei 309) embryogenic suspension cells were studied as a function of various parameters. Mannitol at concentrations of 0.5 and 0.6 M was best for osmotic preconditioning of the cells for transie nt, but not For integrative transformation, for which sucrose yielded the b est and most reliable results. Denaturation of the transforming plasmid DNA Frier to bombardment improved transient and: integrative transformation fr equencies two to three fold. Delivery of double-stranded plasmids in linear form had no effect on transient transformation when compared to supercoile d plasmid DNA, but led to an overall two fold increase in integrative trans formation frequency. This shows that optimized protocols for generating tra nsgenic plants should not be based, exclusively on transient gene expressio n assays.