Functional Analysis of Naturally Integrated Rol Genes in Sweet Potato via CRISPR/Cas9 Genome Editing

Sweet potato (Ipomoea batatas) is a globally important crop and one of a growing number of plants recognized as naturally transgenic, harboring Agrobacterium-derived T-DNA genes whose functions remain largely uncharacterized. In this proof-of-concept study, we applied CRISPR/Cas9 technology to generate targeted knockouts of the Ib-rolB/C and Ib-rolD-like genes located within the sweet potato cellular T-DNA2 (IbT-DNA2) region. Mutations were introduced into sweet potato callus cultures using an optimized genome editing protocol, with most edits consisting of single-nucleotide insertions. Knockout of Ib-rolB/C did not affect callus growth but significantly reduced levels of chlorogenic acid derivatives. Validation in planta using transient expression in I. batatas leaves confirmed the suppressive effect of Ib-rolB/C disruption on polyphenol content. In contrast, Ib-rolD-like knockout lines showed reduced biomass accumulation and downregulation of cell cycle-related genes, but did not display significant changes in metabolite content in either callus cultures or leaf tissues. These findings suggest that Ib-rolB/C and Ib-rolD-like may differentially contribute to growth and secondary metabolism in sweet potato.