Deciphering the complex molecular architecture of the genetically modified soybean FG72 through paired-end whole genome sequencing

Abstract

The clear molecular characterization of genetically modified (GM) plants and animals is a prerequisite for obtaining regulatory approval and safety certification for commercial cultivation. This characterization includes the identification of the transferred DNA (T-DNA) insertion site, its flanking sequences, the copy number of inserted genes, and the detection of any unintended genomic alterations accompanying the transformation process. In this study, we performed a comprehensive molecular characterization of the well-known GM soybean event FG72 using paired-end whole-genome sequencing (PE-WGS). We examined the T-DNA insertion site, flanking sequences, the entire structure and copy number of the T-DNA integration, the presence of plasmid backbone sequences, and genome-wide structural variations (SVs). Our analysis revealed that the T-DNA integrated into two distinct sites on chromosome 15 of the host genome, accompanied by a translocation of host genomic sequences. One site harbored a partial T-DNA integration, while the other site contained two tandem repeats of the full T-DNA. Importantly, no plasmid backbone sequences were detected in the host genome, indicating a clean T-DNA integration during the biolistic transformation process. Furthermore, we identified numerous genome-wide SVs, with chromosome 15 ranking second among all 20 chromosomes in terms of SV frequency, and most of these variations occurring within gene-coding regions. These results provide a refined and comprehensive molecular characterization of the FG72 soybean event, which could further support its commercial approval and cultivation. Our work highlights the utility of the PE-WGS approach as a sensitive and labor-efficient alternative to conventional molecular characterization techniques, generating comprehensive data to facilitate the safety assessment of GM crops during research and commercialization pipelines.