Exogenous titanium dioxide nanoparticles alleviate cadmium toxicity by enhancing the antioxidative capacity of Tetrastigma hemsleyanum

Nanotechnology is one of the most recent approaches employed to defend plants against both biotic and abiotic stress including heavy metals such as Cadmium (Cd). In this study, we evaluated the effects of titanium dioxide (TiO2) nanoparticles (TiO2 NPs) in alleviating Cd stress in Tetrastigma hemsleyanum Diels et Gilg. Compared with Cd treatment, TiO2 NPs decreased leaf Cd concentration, restored Cd exposure-related reduction in the biomass to about 69% of control and decreased activities of antioxidative enzymes. Integrative analysis of transcriptome and metabolome revealed 325 differentially expressed genes associated with TiO2 NP treatment, most of which were enriched in biosynthesis of secondary metabolites. Among them, the flavonoid and phenylpropanoid biosynthetic pathways were significantly regulated to improve the growth of T. hemsleyanum when treated with Cd. In the KEGG Markup Language (KGML) network analysis, we found some commonly regulated pathways between Cd and Cd+TiO2 NP treatment, including phenylpropanoid biosynthesis, ABC transporters, and isoflavonoid biosynthesis, indicating their potential core network positions in controlling T. hemsleyanum response to Cd stress. Overall, our findings revealed a complex response system for tolerating Cd, encompassing the transportation, reactive oxygen species scavenging, regulation of gene expression, and metabolite accumulation in T. hemsleyanum. Our results indicate that TiO2 NP can be used to reduce Cd toxicity in T. hemsleyanum.