The presence of toxic heavy metals lead (Pb) and cadmium (Cd) in polluted soil damage crop production and consequently harms human and livestock health. Tartary buckwheat (Fagopyrum tataricum) is a potential model plant for heavy metal phytoremediation because of its valuable characteristics of high heavy metal tolerance and abundant biomass production. Here, we report that the Tartary buckwheat FtMYB46-FtNRAMP3 module enhances plant Pb and Cd tolerance. RNA sequencing analysis showed that Pb treatment specifically induced expression of FtNRAMP3, a member of the NRAMP (Natural Resistance-Associated Macrophage Protein) transporter gene family. Further cytological and biochemical analysis revealed that FtNRAMP3 was localised to the plasma membrane and significantly contributed to increased tolerance to Pb and Cd in yeast cells. Consistently, transgenic overexpression of FtNRAMP3 in Arabidopsis significantly increased plant tolerance to Pb and Cd applications, reducing Pb concentration but increasing Cd concentration in the overexpression transgenic plants. Subsequent yeast one-hybrid and electrophoretic mobility shift assays showed that the transcription factor FtMYB46 directly binds to the FtNRAMP3 promoter. Further, FtMYB46 promoted FtNRAMP3 expression and increased plant Pb and Cd tolerance. Overall, this study demonstrates the important role of the FtMYB46-FtNRAMP3 module and its potential value in the phytoremediation of Pb and Cd stress.

Aluminum (Al) toxicity is a considerable factor limiting crop yield and biomass in acidic soil. Tartary buckwheat growing in acidic soil may suffer from Al poisoning. Here, we investigated the influence of Al stress on the growth of tartary buckwheat seedling roots, and the alleviation of Al stress by silicon (Si), as has been demonstrated in many crops. Under Al stress, root growth (total root length, primary root length, root tips, root surface area, and root volume) was significantly inhibited, and Al and malondialdehyde (MDA) accumulated in the root tips. At the same time, catalase (CAT) and ascorbate peroxidase activities, polyphenols, flavonoids, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2 '-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) free-radical scavenging ability were significantly decreased. After the application of Si, root growth, Al accumulation, and oxidative damage were improved. Compared to Al-treated seedlings, the contents of O-center dot(2)- and MDA decreased by 29.39% and 25.22%, respectively. This was associated with Si-induced increases in peroxidase and CAT enzyme activity, flavonoid compounds, and free-radical scavenging (DPPH and ABTS). The application of Si therefore has positive effects on Al toxicity in tartary buckwheat roots by reducing Al accumulation in the roots and maintaining oxidation homeostasis.