ABSTRACT
Plants that hyperaccumulate selenium (Se) contain more than 1 mg Se/g DW in their aboveground tissues. 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. The study has identified a number of genes either up-regulated by Se or overexpressed in the hyperaccumulator compared to the non-accumulator, principally involved in antioxidant systems, plant defense, jasmonic acid/salicylic acid/ethylene signaling, S acquisition and assimilation. In a reverse assay, SpATPS2 was inhibited by both sulfate and selenate, but the effect of selenate was less pronounced, thus suggesting a greater affinity of this protein for Se over S. TPS2 gene from Stanleya pinnata, in particular, looks an intriguing candidate for explaining elevate Se assimilation rates and tolerance in this hyperaccumulator, while SULTR1.2 could be responsible for extremely high rates of Se uptake.
