Integrative omics reveals IbADT6 involvement in chlorogenic acid accumulation and stress tolerance in sweet potato

As a major global crop, sweet potato (Ipomoea batatas), is valued for its starch content, versatility, and rich nutritional profile, including polyphenols and chlorogenic acid (CGA). Despite its significance, genetic and molecular research on sweet potato has been constrained by its complex hexaploid genome. Recent advances in genome sequencing have enabled the integration of transcriptomic and metabolomic platforms, facilitating investigation into the regulatory mechanisms of CGA accumulation. Here, we employed a multi-omics approach to analyze CGA synthesis regulation and related polyphenols in sweet potato cultivars with varying CGA contents grown at different planting durations. The results showed that both genotype and planting date significantly influenced CGA accumulation, with extended cropping duration enhancing the expression of key biosynthetic genes such as PAL, C4H, 4CL, C3H, HCT, HQT, and UGT84. Co-expression network analysis identified IbADT6 as a central hub gene involved in phenylalanine synthesis, which was closely associated with CGA accumulation. The functional validation was carried out through the heterologous overexpression (OE) of IbADT6 in tobacco, where it was confirmed to be involved in the enhancement of CGA production, with the transgenic plants exhibiting total CGA content 108.6% higher than wild-type (WT) plants subjected to salt stress (P = 0.0009) and more than double under drought stress (P = 0.0002). Moreover, IbADT6-overexpressing tobacco lines exhibited significantly improved resistance to drought and salt stress, which was associated with increased CGA accumulation and enhanced antioxidant enzyme activities. Under stress conditions, the transgenic lines showed smaller reductions in plant height and biomass, increased activities of antioxidant enzymes such as superoxide dismutase, peroxidase, and catalase, and accumulated lower levels of malondialdehyde, indicating reduced oxidative damage. The results provide a basis for metabolic engineering and molecular breeding for the improvement of the nutritional and industrial value of sweet potato.