Persistence and Bioavailability of Transgenic Genes Released from Genetically Modified Papaya and the Influence on Soil Bacterial Communities in Taiwan

Papaya ringspot virus (PRSV) is the most destructive disease of papaya (Carica papaya L.) in Taiwan, and transgenic papaya resistant to PRSV and PLDMV (papaya leaf distortion mosaic virus) were developed in Taiwan. Horizontal gene transformation (HGT) of kanamycin resistant gene nptII from transgenic papaya, the persistence of transgenic genes in soil samples, and the influence of transgenic papaya on the soil diversity of microorganisms were reported. Two strains of Acinetobacter sp. BD413 and BD413 (pFG4 nptII) were used as recipient cells, and no transformation was detected in both bacteria when transgenic papaya genomic DNA were added. However, transformations were detected in Acinetobacter sp. BD413 (pFG4 nptII) on filter and in soil microcosms when PCR products of different lengths (1396, 786, and 604 bp, contained nptII) amplified from transgenic papaya DNA were added. The persistence of transgenic gene of 398 bp (located between plasmid pBI121 and NOS terminator, pBI121/NOS-T) in soil was 0.06 g g soil, whereas the residues of 769 bp (located between 35S promoter and coat protein, 35S-P/PRSV-CP) and 200 bp (located between NOS promoter and nptII gene, NOSP/nptII) were less than 30 pg g soil (detection limit). The influence of transgenic papaya on the soil diversity of microorganisms were conducted by DGGE (Denaturing Gradient Gel Electrophoresis) method, and the results showed that some differences appeared on the bacterial DGGE patterns at the beginning of planting, but the difference reduced after six months. _____________________________________________________________________________________________________________