Efforts to deregulate Rainbow papaya in Japan: Molecular characterization of transgene and vector inserts

Transformation plasmid-derived insert number and insert site sequence in 55-1 line papaya derivatives Rainbow and SunUp was determined as part of a larger petition to allow its import into Japan (Suzuki et al., 2007, 2008). Three insertions were detected by Southern analysis and their corresponding sequences determined by clones (Fermín, 2002) or via the whole genome shotgun (WGS) sequence database of SunUp (Ming et al., 2008). All functional transgenes including the coat protein (CP) gene that confers resistance to PRSV, and visible and selectable marker genes, uidA encoding glucuronidase (GUS) and nptII encoding neomycin phosphotransferase II were found in a single 9,789 basepair (bp) insert referred to as the functional transgene. The two other insertion sites consisted of a 290 bp nonfunctional sequence of the nptII gene and a 1,533 bp plasmid-derived fragment containing a nonfunctional 222 bp segment of the tetA gene. Detection of the same three inserts in Rainbow and in samples of SunUp representing transgenic generations five to eight (R5 to R8) suggests that the inserts are stable. Five out of the six genomic DNA segments flanking the three inserts were nuclear plastid sequences (nupts). No changes to endogenous gene function based on sequence structure of the transformation plasmid DNA insertion sites could be determined and no allergenic or toxic proteins were predicted from analysis of the insertion site and flanking genomic DNA. These results should support a positive review of the petition to allow the import and consumption of Rainbow and its derivatives in Japan, which is currently in its final stages. Export of Rainbow papaya to Japan will greatly benefit the local papaya industry in Hawaii and will provide a case for testing consumer acceptance of genetically engineered fresh products in Japan