Natural sweet potato transgene Ib-rolB/C enhances abiotic and biotic stress tolerance through redox and defense regulation.

Abstract

Main conclusion: Natural sweet potato transgene Ib-rolB/C enhances abiotic and biotic stress tolerance through coordinated regulation of ROS signaling, antioxidant defense, immune activation, and secondary metabolism. Horizontal gene transfer from Agrobacterium has contributed to plant genome evolution, yet the physiological roles of naturally integrated T-DNA genes remain poorly understood. Cultivated sweet potato (Ipomoea batatas) contains two cellular T-DNA regions, including the IbT-DNA2 locus harboring the naturally acquired gene Ib-rolB/C. Here, we investigated the stress-responsive expression and functional significance of Ib-rolB/C using transgenic Arabidopsis thaliana. The gene was strongly induced by cold, heat, and salinity. Moreover, Ib-rolB/C-expressing plants exhibited enhanced tolerance to abiotic stresses during germination, as well as increased resistance to Pseudomonas syringae and Botrytis cinerea. These phenotypes were associated with moderate ROS accumulation, enhanced antioxidant capacity, elevated GSH/GSSG ratios, reduced lipid peroxidation, and elevated basal expression of stress- and defense-related genes. In addition, Ib-rolB/C expression induced substantial metabolic reprogramming characterized by increased accumulation of flavonol glycosides and camalexin together with reduced glucosinolate levels. Our findings demonstrate that Ib-rolB/C functions as a multifunctional regulator integrating redox signaling, stress adaptation, immune responses, and secondary metabolism, highlighting the evolutionary significance of naturally acquired T-DNA genes in plants.