Multigene Coexpression (HMA9-CadWp-ZIP6) Enables Cadmium-Hyperaccumulating Transgenic Poplar for Efficient Soil Remediation

Poplar shows promise for cadmium (Cd(II)) phytoremediation
due
to its rapid growth and high biomass yet lacks hyperaccumulation capacity.
Here, the ZIP and HMA gene families
were identified in poplar. Under Cd(II) stress, ZIP6 expression in poplar roots decreased, while HMA9 expression increased over time. CadWp can chelate Cd(II) in vitro.
Overexpression (OE) and reduced expression (RE) transgenic poplar
lines of these genes were generated. OE/RE ZIP6 lines
demonstrated that this gene enhanced Cd(II) absorption in roots, while
OE/RE HMA9 lines demonstrated that this gene facilitated
Cd(II) transport. OE CadWp in poplar largely alleviates
the toxicity of Cd(II). Then, poplar lines (OE 9HCZ) with simultaneous overexpression of HMA9-CadWp-ZIP6 were generated and accumulated higher Cd(II) levels with a minimal
growth penalty. In summary, we identified genes involved in Cd(II)
absorbing, transporting, and detoxification, and coexpression of these
genes in poplar enabled the development of new biomaterials for Cd(II)-contaminated
soil phytoremediation.