Acetosyringone and osmoprotectants like betaine or proline synergistically enhance Agrobacterium-mediated transformation of apple.

The effects of the plant signal molecule acetosyringone (AS) and the osmoprotectant betaine phosphate (BP) have been examined for their ability to increase the transformation efficiency of Agrobacterium tumefaciens (At), C58C1::pGV3850 harboring the binary vector pKIWI105. This binary plasmid encodes the β-glucuronidase (GUS) gene and was previously shown to be expressed exclusively in plant tissues. Bacteria were grown in one of two previously reported virulence induction media (MS20 and SIM) for 5h and GUS activity was measured fluorimetrically in individual 6 week old leaf discs as a quantitative measure of stable transformation events. Bacteria induced in MS20 supplemented with AS (0.1 mM) and BP (1 mM) showed a significant increase in GUS activity as compared to media containing AS or BP added singly or control media lacking the supplements. The effects of another osmoprotectant proline (1 mM) could replace the beneficial effects of betaine. No significant difference was observed among treatments with respect to the two induction media.