Overexpression of NtGPX8a Improved Cadmium Accumulation and Tolerance in Tobacco (Nicotiana tabacum L.)

Cadmium (Cd)-induced oxidative stress detrimentally affects hyperaccumulator growth, thereby diminishing the efficacy of phytoremediation technology aimed at Cd pollution abatement. In the domain of plant antioxidant mechanisms, the role of glutathione peroxidase (GPX) in conferring Cd tolerance to tobacco (Nicotiana tabacum) remained unclear. Our investigation employed genome-wide analysis to identify 14 NtGPX genes in tobacco, revealing their organization into seven subgroups characterized by analogous conserved domain patterns. Notably, qPCR analysis highlighted NtGPX8a as markedly responsive to Cd2+ stress. Subsequent exploration through yeast two-hybridization unveiled NtGPX8a's utilization of thioredoxins AtTrxZ and AtTrxm2 as electron donors, and without interaction with AtTrx5. Introduction of NtGPX8a into Escherichia coli significantly ameliorated Cd-induced adverse effects on bacterial growth. Transgenic tobacco overexpressing NtGPX8a demonstrated significantly augmented activities of GPX, SOD, POD, and CAT under Cd2+ stress compared to the wild type (WT). Conversely, these transgenic plants exhibited markedly reduced levels of MDA, H2O2, and proline. Intriguingly, the expression of NtGPX8a in both E. coli and transgenic tobacco led to increased Cd accumulation, confirming its dual role in enhancing Cd tolerance and accumulation. Consequently, NtGPX8a emerges as a promising candidate gene for engineering transgenic hyperaccumulators endowed with robust tolerance for Cd-contaminated phytoremediation.