Characterization of rice transformed via an Agrobacterium-mediated inflorescence approach

Rice inflorescences were inoculated with Agrobacterium tumefaciens strain LBA4404 carrying plasmid pJD4 with application of vacuum infiltration. After co-cultivation, callus was initiated and subjected to hygromycin selection, and plants were regenerated from resistant callus lines. Based on the total number of co-cultivated inflorescences bearing flowers 1 to 3 mm in length, the average frequency for recovering independent transgenic rice plants was at least 30%. Seeds from selfed R0 plants were harvested within 6 months after initiation of the experiments. Genomic DNA blot analysis showed that genes in the T-DNA of the binary plasmid were stably integrated into the rice genome, typically at low copy number. In most, but not all, cases the transgene was transmitted to R1 progeny at a frequency characteristic for Mendelian inheritance of a single dominant trait. For selfed progeny of one two-locus insertion line, reactivation of GUS expression was observed for a single copy locus that segregated from a silenced multicopy locus. For this line and some additional plants, fluorescence in situ hybridization was used to visualize the chromosomal location of the transgene insert.