Efficient transformation and regeneration of rice small cell groups.

Transgenic plants have been regenerated from small cell groups of rice using a simpler, faster, and more efficient method than used previously (e.g., protoplast transformation and regeneration methods). Small cell groups of 50-100 cells were prepared from established suspension cultures of rice cell lines. Transformation of small cell groups with intact cell walls was carried out with a plasmid harboring the beta-glucuronidase gene and was mediated by polyethylene glycol. Assay of beta-glucuronidase activity indicated that the frequency of transformation was about 7%. beta-Glucuronidase activity was detected in the roots and leaves of plants regenerated from transformed calli. One or two copies of the beta-glucuronidase gene per cell were determined to be integrated into the rice chromosomal DNA isolated from transformed calli. This method of transformation and regeneration is widely applicable to both dicotyledonous and monocotyledonous plants, especially those varieties that are resistant to regeneration from protoplasts.