The identification of the key genes regulating plant tolerance to Zn stress is important for enhancing the Zn phytoremediation of targeted plants. Here, we showed that the T-DNA insertion-induced inhibition of the BRUTUS (BTS) gene in the bts-1 mutant greatly improved Zn tolerance, as indicated by increased biomass production and reduced leaf chlorosis. The ProBTS::BTS-GFP complementation in the bts-1 mutant abolished the improvement of Zn tolerance. Unexpectedly, the bts-1 mutant had higher and comparable Zn concentrations in the roots and citrate effluxer shoots, respectively, compared to wild-type plants. As a result, the shoots and roots of bts-1 mutants had 53% and 193% more Zn accumulation than the wild-type plants, respectively. RNA-seq analyses revealed that the Fe nutrition-related genes were upregulated in bts-1 mutants, especially under Zn stress conditions. Therefore, the bts-1 mutants had a greater Fe concentration and a higher Fe/Zn ratio than the wild-type plants exposed to Zn toxicity. Further study showed that the differences in Zn tolerance between bts-1 and wild-type plants were minimized by eliminating Fe or supplementing excessive Fe in the growth medium. Taken together, the T-DNA insertion-induced inhibition of BTS improves plant Zn tolerance by optimizing Fe nutrition; thus, the knockdown of BTS may be a promising approach for improving Zn phytoremediation efficiency.
Keywords: Zn phytoremediation; biotechnological method; iron nutrition; metal ions homeostasis.