[Studies of the integration and expression of exogenes in transgenic rice obtained via particle bombardment...

Various integration events from simple to complex have been found in transgenic elite rice varieties, which were co-transformed with bar and cecropin B gene by particle bombardment after system studies of the structure and expression of the transgene. It was displayed that there were one to seven insertion loci and one to ten copies of transgene in different transformants. No absolute correlation was found between the numbers of transgene copies and the gene expression. Different level expression of transgenes with similar insertion mode was also discovered. The expression cassette integrity and transcription frequency of selectable bar gene were more than non-selectable cecropin B gene, whereas gene silence in plants integrated with intact bar gene was found and higher expression level of cecropin B gene with 0.6 kb fragments degraded in terminator was deduced.