Production and Characterization of Transgenic indica Rice Plants Carrying Maize Ac-Ds Elements Introduced by Particle Bombardment.

Following a few reports on indica rice transformation, we demonstrated the recovery of transgenic indica rice cultivars carrying potentially useful genes through co-transformation with a selectable marker using a particle bombardment method (biolistic process). Scutellum-derived calli and embryos of 3 selected indica rice cultivars were used as explants. Co-transformation with selectable bar gene was employed to isolate transformed callus lines that are resistant to the herbicide bialaphos. Subsequently, bialaphos-resistant calli were regenerated and 29% of R0 plants were shown to possess Ac and Ds by PCR analysis. About 50% of the putative R0 transformants showed transmission of the transgene based on PCR and Southern blot analyses, indicating that a large number of primary transformants represented chimeric individuals, or that elimination of the transgenes eventually occurred during meiosis/mitosis. PCR-positive R0 plants were self-pollinated to produce R1 lines. Single and multiple integrative events were detected and R1 progenies from 3 transgenic lines exhibited the expected Mendelian inheritance pattern. Although a few rearranged copies of the transgenes were noted, a majority of the copies remained intact after integration. Expression of the CaMV35S-driven transposase gene was revealed by the presence of the transposase transcript in Northern blots. The procedure described here provides an applicable tranformation system that can be further improved to generate more Ac and Ds lines towards establishing a functional transposon mutagenesis system in indica rice.