Frequency of mutations of the transgene, which might result in the loss of the glyphosate-tolerant phenotype, was lowered in Roundup Ready® soybeans

Polymerase chain reaction (PCR) primers were prepared to amplify the DNA fragment between the genomic DNA sequence adjacent to the 5'-integration site of Roundup Ready (R) (RR) soybeans neighboring the transgene and the parts of the coding region of the transgene, together with the primer set for the internal host gene, the alpha' subunit of p-conglycinin storage protein gene (Cong gene). Using the primers for the transgene and Cong gene, the DNA fragments were amplified from the individual genomic DNAs prepared from 72 samples of RR soybean isolated from imported soybean seeds labeled "not segregated.'' Although the frequency of alterations of the nucleotide sequences in both the transgene and Cong gene were almost the same, the mutations that caused alterations to the amino acid sequence were more highly repressed in the transgene than in the Cong gene. In the nucleotide sequence upstream of the coding region of the transgene, the number of alterations of the nucleotide in the proximal promoter region was smaller than that in the further upstream region, suggesting that the mutants missing or being weak glyphosate-tolerance by an alteration of the critical nucleotide sequences in the promoter or coding region might be discarded artificially. It is supposed that the selective bias on the transgene might be extremely high, which indicates that the nucleotide sequence of the transgene might be stable and maintained in inbred RR soybean lines.