ABSTRACT
Plants that hyperaccumulate selenium (Se) contain more than 1 mg Se/g DW in their aboveground tissues (Schiavon & Pilon-Smits 2017). The capacity to hyperaccumulate and hypertolerate Se by these species possibly developed as a result of convergent evolution of selective transporters and biochemical pathways in distinct angiosperm clades during geological periods when Se in soil was widely abundant and more widespread than today (White 2015). Some of the mechanisms evolved by Se hyperaccumulators are those involved in the regulation of specific Se/sulfur (S) transporters, methylation of Se-amino acids, rupture of Se-cysteine (Se-Cys) into alanine and elemental Se, and volatilization of Se-organic compounds (Schiavon & Pilon-Smits 2017, Lima et al. 2018). Additional mechanisms might include oxidation and transamination of selenocysteine (Secys), and conversion of SeCys to selenomethionine (SeMet) (Zhou et al. 2018).
