T-LOC: A comprehensive tool to localize and characterize T-DNA integration sites

Scientists have developed many approaches based on PCR or next-generation sequencing to localize and characterize integrated T-DNAs in transgenic plants generated by Agrobacterium tumefaciens-mediated T-DNA transfer. However, none of these methods has the robust ability to handle all transgenic plants with diversified T-DNA patterns. Utilizing the valuable information in the whole-genome sequencing data of transgenic plants, we have developed a comprehensive approach (T-LOC) to localize and characterize T-DNA integration sites (TISs). We evaluated the performance of T-LOC on genome sequencing data from 48 transgenic rice (Oryza sativa) plants that provide real and unbiased resources of T-DNA integration patterns. T-LOC discovered 75 full TISs and reported a diversified pattern of T-DNA integration: the ideal single-copy T-DNA between two borders, multiple-copy of T-DNAs in tandem or inverted repeats, truncated partial T-DNAs with or without the selection hygromycin gene, the inclusion of T-DNA backbone, the integration at the genome repeat region, and the concatenation of multiple ideal or partial T-DNAs. In addition, we reported that DNA fragments from the two A. tumefaciens plasmids can be fused with T-DNA and integrated into the plant genome. Besides, T-LOC characterizes the genomic changes at TISs, including deletion, duplication, accurate repair, and chromosomal rearrangement. Moreover, we validated the robustness of T-LOC using PCR, Sanger sequencing, and Nanopore sequencing. In summary, T-LOC is a robust approach to studying the TISs independent of the integration pattern and can recover all types of TISs in transgenic plants.