Efficient transformation of rice protoplasts mediated by a synthetic polycationic amino polymer

 A very simple and efficient transformation system for rice was established using a synthetic polycationic amino polymer (polycation). Improvements in the culture conditions, especially filtration of the suspension cells before and after protoplast culture, greatly contributed to a large yield of high-quality protoplasts and an increased ability of the cells to regenerate. Transformation parameters, such as the ratio of DNA and polycation concentrations, preincubation of the DNA and polycation prior to DNA transfer, and precentrifugation and resuspension of protoplasts before DNA transfer, were analyzed. Fertile transgenic plants containing the bar gene were selected and shown to demonstrate resistance against high concentrations of bialaphos. Southern blot analysis showed four to nine bands representing the bar gene in polycation-mediated transgenic rice plants compared with two to three bands in electroporation-mediated transgenic rice plants. The regeneration efficiency of the polycation-mediated method was compared to that of the electroporation-mediated method; while the polycation-mediated method tended to show a relatively lower regeneration rate, regenerants showed a normal phenotype. Received: 26 February 1998 / Accepted: 15 May 1998