High levels of regeneration and optimized transient expression factors are critical for increasing transformation rates in plant species. An efficient regeneration protocol was developed and transient expression experiments were carried out to provide information for the improvement of Agrobacterium tumefaciens mediated transformation system in Japanese plum (Prunus salicina Lindl.). Five different varieties of Japanese plum ('Shiro', 'Early Golden', 'Gladstone', 'Red Heart' and 'Bruce'), four different basal salt mixtures (QL, WPM, B5 and MS), light regimes and TDZ pretreatments were evaluated to optimize adventitious shoot regeneration. Regeneration ability was highly variety dependent. Basal salt composition significantly affected the regeneration frequency. Best regeneration frequencies were obtained from 'Shiro' (56.4%) on QL salts and 'Early Golden' (42.8 %) on B5 medium. Subsequently transient expression experiments were carried out using three Agrobacterium tumefaciens strains; LBA4404, EHA105 and GV3101, each containing binary vector pCAMBIA2301. There were significant differences observed among Agrobacterium strains tested. Agrobacterium strains LBA4404 and EHA105 were much more effective than GV3101 strain and the presence of acetosyringone in the co-cultivation medium resulted in increased GUS expression